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The solid-solution aqueous-solution (SSAS) system often involves dissolution/precipitation and redox reactions simultaneously. Comprehensive understanding of the SSAS system requires mechanistic insights into the dissolution mechanism of the solid solution based on reliable characterisation of the solid phases. Given this background, this study investigates the dissolution behaviour of zirconium–cerium oxide solid solution ((Zr,Ce)O2/(Ce,Zr)O2), which contains the redox-active metal Ce (Ce(III / IV)) and is of particular importance in the nuclear industry. The solid phases of the solid solution were comprehensively characterised by powder X-ray diffraction (PXRD) with Rietveld analysis and X-ray absorption spectroscopy (XAS) with factor analysis, indicating that the solid solution was primarily composed of tetragonal-(Zr,Ce)O2 and cubic-(Ce,Zr)O2. Water immersion of the solid solution leads to the dissolution of the solid phase at the solid–liquid interface. The addition of a reductant to the system reduces Ce(IV) in the solid solution to -(III) at the surface, promoting the dissolution of Ce from the solid-solution phase. The release of Ce from the solid solution also enriches the Zr content in the remaining solid-solution phase at the surface, which makes it more insoluble. This results in the formation of a protective layer at the solid surface, retarding further dissolution of the solid-solution phase. [ABSTRACT FROM AUTHOR]

The traditional impregnation method for preparing supported catalysts often faces challenges such as particle agglomeration and weak support–metal interactions. This study focuses on utilizing the exsolution method to prepare Fe, Co, and Ni supported catalysts from ABO3-type perovskites, aiming to overcome these challenges. Experimental results show that LaBO3 perovskites with different B site metals (B = Fe, Co, Ni) exhibit different metal exsolution kinetics in the ammonia synthesis reaction. LaNiO3 demonstrates an initial activity of 782.2 μmol g−1 h−1 within the first 2 hours of the reaction, maintaining stability beyond 80 hours. In contrast, LaFeO3 and LaCoO3 exhibit prolonged initiation periods for the metal exsolution process, reaching activities of 7873.8 μmol g−1 h−1 and 8046.7 μmol g−1 h−1, respectively, after approximately 80 hours. The degree of B-site metal exsolution was investigated using X-ray absorption fine structure (XAFS) and Rietveld refinement of XRD data, revealing exsolution rates of 72.03%, 69.3%, and 86.3% for Fe, Co, and Ni, respectively, after 80 hours of reaction. This study not only introduces the exsolution method for ammonia synthesis but also empirically validates several computational predictions, thereby supporting both theoretical and practical research. [ABSTRACT FROM AUTHOR]

Crystals of Ca10.5−xTMx(VO4)7 (TM = Co, Cu), belonging to the whitlockite family, were synthesized by solid-state reaction and studied as a function of the TM content (x) for the first time. The structure was refined at ambient conditions and at high temperatures up to 1200 K using the Rietveld method. The unit cell size significantly decreases with increasing TM content up to the solubility limit, xlim, which is 0.78(3) for TM = Co and 0.75(4) for TM = Cu. Occupancy factors show a preference for the M5 site by Co/Cu. The unit cell size varies smoothly with temperature, while the axial ratio exhibits nonlinear behaviour above approximately 800 K. The thermal expansion coefficient was determined from 300–1100 K. Atomic arrangement modifications at higher temperatures are indicated by changes in the axial ratio, the thermal expansion coefficient, and the reduction of fractional TM occupancy at the M5 site at specific temperatures. [ABSTRACT FROM AUTHOR]

A number of phosphomolybdic acid dispersed on SBA-15 catalysts with structural defects and strong acidity were synthesized and applied for the production of ultralow sulfur diesel. The oxygen defect concentration in the catalysts was quantitatively determined by the Rietveld refinement method. These catalysts contained many Brønsted (B) and Lewis (L) acid sites (648 to 1479 μmol g−1) depending on the heteropolyacid content and the thermal treatment. The Mo5+/Mo6+ ratio calculated by XPS technique varied from 0.21 to 0.27%, indicating the creation of oxygen defects in the Keggin unit. The area under the IR absorption band at 980 cm−1 (characteristic of the Mo＝O bond) in the FTIR spectra of different catalysts was found to be inversely proportional to the variation of L acidity as a function of temperature, indicating that oxygen defects are the origin of the L acidity. In the oxidation reaction for removing dibenzothiophene, DBT, from a model diesel, the DBT conversion correlated well with the oxygen defect concentration and total surface acidity, confirming that the surface acidity and oxygen defects played key roles in DBT adsorption and oxidation. Almost 100% DBT conversion was achieved on the best 30 wt% H3PMo12O40/SBA-15 catalyst under the optimal reaction conditions (reaction time 60 min, reaction temperature 70 °C, H2O2/DBT molar ratio 6–8, catalyst concentration 2–2.5 mg ml−1, and hydrogen peroxide to formic acid molar ratio 1.5). A novel mechanism of the DBT oxidative removal in a biphasic system involving the participation of the neighboring L and B acid sites, oxygen defects, and the formation of peroxometallic and superoxometallic species was proposed. [ABSTRACT FROM AUTHOR]

Na2/3Mn2/3Fe1/3O2 layered oxides were synthesized using an enhanced solid-state synthesis method. Analysis via XRD confirmed the high purity of the prepared samples. Rietveld refinement of the crystal structure revealed that the synthesized materials adopt a rhombohedral system with the P63/mmc space group and P2 structure type. Calorimetric study confirms the presence of two-phase transitions at 393 K and 433 K. Vibrational investigation conducted using IR spectroscopy demonstrated the presence of an MO6 group. The dielectric properties of the material were evaluated over a frequency range of 0.1–107 Hz across temperatures ranging from 313 K to 453 K. The study of the real part of the dielectric permittivity using impedance spectroscopy suggested a high dielectric constant at low frequency and indicated the existence of both space charge and dipolar polarizations. The dielectric losses were analyzed according to the Giuntini law to extract the relaxation process. As a result, the module revealed two relaxations attributed to grain boundaries and grain relaxations. The frequency-dependent conductivity was interpreted following Jonscher's law. The variation of the power law exponent with temperature, corresponding to the grains s1 and s2, suggests that the conduction behavior of the P2-Na2/3Mn2/3Fe1/3O2 compound can be ascribed to the NSPT and CBH models. [ABSTRACT FROM AUTHOR]

The new lithium arsenidotetrelates Li8SiAs4, Li8GeAs4, Li14SiAs6, Li14GeAs6 and Li14SnAs6 were synthesized via ball milling and structurally characterized by Rietveld analysis of X-ray powder diffraction data. The aliovalent substitution of lithium in hexagonal Li3As by introducing a tetravalent tetrel cation stabilizes cubic structures for Li8TtAs4 (Tt = Si, Ge) in the space group Pa3¯ and for the lithium richer compound Li14TtAs6 (Tt = Si, Ge, Sn) in the higher symmetrical space group Fm3¯m (no. 225). Thermal properties of the arsenidotetrelates were investigated via high temperature powder diffraction and differential thermal analysis revealing a decomposition process of the lithium richer arsenidotetrelate (Li14TtAs6 → Li8TtAs4 + 2Li3As) into the lithium poorer arsenidotetrelates and lithium arsenide at moderate temperatures. Impedance spectroscopy shows moderate to good lithium ion conductivity for the lithium arsenidotetrelates. [ABSTRACT FROM AUTHOR]

Owing to the occupying tendency of Mn4+ at octahedral sites, doping Mn4+ activators in tetrahedral structures poses challenges and hence is seldom reported. In this work, tetrahedrally sited Mn4+ phosphors were studied. By combining X-ray diffraction (XRD) data with Rietveld refinement analysis, the location of Mn4+ was determined. It was found that by adding excessive raw MgO, the phosphor synthesis temperature can be improved, enhancing the crystallinity of the crystal and thus improving the emission performance of the phosphor. In addition, excessive raw MgO forms a second phase in an LMGO matrix, which does not change the doping site for Mn4+. The Tanabe–Sugano diagram of Mn4+ in the tetrahedral field and the energy-level diagram of these phosphors were constructed for the first time, and the excitation and emission mechanisms are discussed in detail. With 1.2-fold excess of raw MgO, the prepared sample (LMGO-Mn-1.2) shows the best luminescence, demonstrating red emissions peaked at 656 nm and affording an emission intensity enhancement of over 50 times compared to a stoichiometric LMGO:Mn4+ system. At 150 °C, LMGO-Mn-1.2 keeps 90% emission intensity compared to that at room temperature. Finally, a high-efficiency warm white light–emitting diode was built. This work provides new insights into the study of Mn4+-activated phosphors in a tetrahedron crystal field. [ABSTRACT FROM AUTHOR]

Owing to the occupying tendency of Mn4+ at octahedral sites, doping Mn4+ activators in tetrahedral structures poses challenges and hence is seldom reported. In this work, tetrahedrally sited Mn4+ phosphors were studied. By combining X-ray diffraction (XRD) data with Rietveld refinement analysis, the location of Mn4+ was determined. It was found that by adding excessive raw MgO, the phosphor synthesis temperature can be improved, enhancing the crystallinity of the crystal and thus improving the emission performance of the phosphor. In addition, excessive raw MgO forms a second phase in an LMGO matrix, which does not change the doping site for Mn4+. The Tanabe–Sugano diagram of Mn4+ in the tetrahedral field and the energy-level diagram of these phosphors were constructed for the first time, and the excitation and emission mechanisms are discussed in detail. With 1.2-fold excess of raw MgO, the prepared sample (LMGO-Mn-1.2) shows the best luminescence, demonstrating red emissions peaked at 656 nm and affording an emission intensity enhancement of over 50 times compared to a stoichiometric LMGO:Mn4+ system. At 150 °C, LMGO-Mn-1.2 keeps 90% emission intensity compared to that at room temperature. Finally, a high-efficiency warm white light–emitting diode was built. This work provides new insights into the study of Mn4+-activated phosphors in a tetrahedron crystal field. [ABSTRACT FROM AUTHOR]

Research into red phosphors with a high color rendering index is particularly compelling, given the absence of a red component in the spectrum of commercial pc-WLEDs, which combine blue LED chips with yellow-emitting YAG:Ce3+ phosphors. Herein, we reported a novel Eu3+ activated Ca3Zn3Te2O12 red-emitting phosphor, synthesized using a conventional high-temperature solid-phase method. The phase and crystal structures were analyzed by powder X-ray diffraction and Rietveld refinement. The optimal excitation peak of the Ca3Zn3Te2O12:Eu3+ phosphor was located at 395 nm, matching those of conventional commercial near-ultraviolet chips. In addition, the Ca3Zn3Te2O12:9%Eu3+ phosphor exhibited good thermal stability, with an activation energy of 0.267 eV, and the CIE color coordinates hardly changed with temperature. Ultimatel, a high-quality white LED device was fabricated by combining Ca3Zn3Te2O12:9%Eu3+ red phosphor, a commercial BaMgAl10O17:Eu2+ blue phosphor, and(Ba,Sr)2SiO4:Eu2+ green phosphor with a 395 nm near-UV chip. Despite a substantial increase in the input current from 20 to 320 mA, the white-LED maintained a stable color rendering index of around 80, highlighting its consistent performance. These results indicated that Eu3+ activated Ca3Zn3Te2O12 phosphors are promising red emission candidates for white LEDs pumped by near ultraviolet chips. [ABSTRACT FROM AUTHOR]

LiFe1−xMnxPO4 with elevated energy density is becoming the next-generation olivine-type cathode. However, its long cycling stability and delivered capacities are far from perfect, chiefly induced by its intrinsically poor ionic/electrical conductivities, sluggish electrode kinetics and notable Jahn–Teller effects upon charge/discharge cycles. Aimed at overcoming these barriers, we herein propose an efficient synergistic fluorine (F)/indium (In) dual doping strategy. As confirmed from the XRD Rietveld refinement results, the doped electronegative F can interact with Mn, thereby shortening Mn–O bond lengths, strengthening the covalent bonding nature and inhibiting the Jahn–Teller distortion/Mn dissolution, whereas the In doping helps to increase the electronic conductivity of particle cathodes, and opens up the crystal lattice spacing for expediting Li+ diffusion. As a proof-of-concept demonstration, the developed F/In-doped LiFe0.5Mn0.5PO4 cathodes exhibit less adverse phase variations, showing a maximum output capacity of 158.5 mA h g−1 at 0.1C, a capacity retention ratio over 86.7% after 500 cycles, and a markedly improved Mn discharge plateau capacity and capacity retention rate (at 2C). This work may not only shed new light on understanding the anion/cation co-doping effects for LiFe1−xMnxPO4, but also offer an applicable concept to design other high-energy-density electrode species. [ABSTRACT FROM AUTHOR]

Developing new photocatalysts and deciphering the structure–property relationship are always the central topics in photocatalysis. In this study, a new photocatalyst Ba3SnGa10O20 containing two d10 metal cations was prepared by a high temperature solid state reaction, and its crystal structure was investigated by Rietveld refinements of monochromatic X-ray powder diffraction data for the first time. There are 2 Ba, 4 metal cations and 6 O independent atoms in a unit cell. Sn4+ and Ga3+ co-occupy the octahedral cavities named M1 and M2 sites, and the other two metal sites are fully occupied by Ga3+. Rational In3+-to-Ga3+ substitution was performed to reduce the potential of the conduction band minimum and enhance the light absorption ability, which was indeed confirmed using UV-vis diffuse reflectance spectra and Mott–Schottky plots for Ba3SnGa10−xInxO20 (0 ≤ x ≤ 2). Interestingly, In3+ exhibits site selective doping at M1 and M2 sites exclusively. With the light absorption ability enhanced, the photocatalytic overall water splitting activity was also improved, i.e. the photocatalytic H2 generation rate was 1.7(1) μmol h−1 for Ba3SnGa10O20, and the optimal catalyst Ba3SnGa8.5In1.5O20 loaded with 1.0 wt% Pd exhibited the H2 generation rate of 27.5(4) μmol h−1 and the apparent quantum yield at 254 nm was estimated to be 2.28% in pure water. [ABSTRACT FROM AUTHOR]

We present a facile and versatile strategy for enabling CsPbI3 rods to self-assemble at an air-water interface. The CsPbI3 rods, which float at the air-water interface, align under the influence of the rotational flow field due to the vortex motion of a water subphase. The aligned CsPbI3 rods could be transferred onto various substrates without involving any sophisticated instrumentation. The temperature of the subphase, the concentration of the CsPbI3 aliquot, the rotational speed inducing vortex motion, and the liftoff position and angle of the substrate were optimized to achieve high coverage of the self-assembled rods of CsPbI3 on glass. The Rietveld refinement of the XRD profile confirms that the aligned CsPbI3 is in the pure orthorhombic phase ascribed to the Pnma space group. The hydrophilic carboxylic group of the oleic acid attaches to the Pb atoms of the halide perovskite rods, while their hydrophobic tails encapsulate the rods within their shell, creating a shielding barrier between the water and the perovskite surface like a reverse micelle. The aligned CsPbI3 rods exhibit a nearly 47-fold increment in current upon exposure to ammonia gas (amounting to 5.6 times higher sensitivity in ammonia sensing) compared to the nonaligned CsPbI3 rods. [ABSTRACT FROM AUTHOR]

The issue of preserving carbonatic stones of cultural heritage (CH) restored in the past that have undergone new decay phenomena is strongly emerging and conservation science has not yet found a reliable solution. In this paper, we propose the application of synchrotron radiation X-ray diffraction computed tomography (XRDCT) to explore the effects of using inorganic-mineral products (ammonium oxalate; ammonium phosphate) in sequence as a novel, compatible and effective re-treatment approach to consolidate decayed carbonatic stones already treated with inorganic-mineral treatments. High-quality XRDCT datasets were used to qualitatively/quantitatively investigate and 3D localize the complex mixture of crystalline phases formed after the conservation re-treatments within a porous carbonatic stone substrate. The XRDCT reconstruction images and the structural refinements of XRD patterns with the Rietveld methods showed that the phase composition of reaction products, their volume distribution, and weight fraction vary as a function of the treatment sequence and penetration depth. The high potential of XRDCT allows (i) assessment of peculiar trends of each treatment/treatment sequence; (ii) exploration of the reaction steps of the sequential treatments and (iii) demonstration of the consolidating effect of inorganic re-treatments, non-destructively and at the micron scale. Above all, our study (i) provides new analytical tools to support the conservation choices, (ii) showcases new analytical possibilities for XRDCT in conservation science, including in investigations of CH materials and decay processes, and (iii) opens up new perspectives in analytical chemistry and material characterisation for the non-destructive and non-invasive analysis of reactions within heterogeneous polycrystalline systems. [ABSTRACT FROM AUTHOR]

For further development of light sources, white light-emitting diodes (wLEDs) have attracted widespread attention as promising next-generation light sources fabricated via the combination of phosphors and LED chips. However, latent defects, such as chemical/thermal instability, low color rendering index (CRI) and high correlated color temperature (CCT), of current mainstream wLEDs seriously hinder their further large-scale implementation. Herein, in order to overcome these limitations, single-phase color-tunable gaudefroyite (Ca3Y(GaO)3(BO3)4 (CYGB)) tridoped with Bi3+/Tb3+/Eu3+ ions was synthesized for the first time and detailed characterisation was performed via high-temperature solid-state reaction and structural/spectral analyses, respectively. Radius difference percentage calculations and Rietveld refinements indicate that dopants occupy both Y3+ and Ca2+ sites but preferably the Y3+ site over the Ca2+ site due to the same valence state. Through subtly regulating the (co)doping contents and skillfully utilizing the energy transfer (ET) strategy from the allowed transition of blue light-emitting Bi to the forbidden transition of green/red light-emitting Tb/Eu, the color hue (including white light) of highly efficient PL can be easily tuned according to the need. Meanwhile, composition/content-optimized white light-emitting CYGB:2%Bi/10%Tb/12%Eu also shows splendid chemical/thermal stability. Finally, as a proof-of-concept experiment, the CYGB:2%Bi/10%Tb/12%Eu phosphor-converted wLED (pc-wLED) was fabricated and encapsulated via the up-to-date remote 'capping' method, which imparted attractive performances. Altogether, the stable CYGB:Bi/Tb/Eu phosphor is a promising candidate for application in lighting/display fields. [ABSTRACT FROM AUTHOR]

Achieving high luminescent quantum yield and thermal stability of phosphors simultaneously remains challenging, yet it is critical for facilitating high-power white light emitting diodes (WLEDs). Herein, we report the design and preparation of the layered structure BaZnB4O8:xEu3+ (0.10 ≤ x ≤ 0.60) red phosphors with high quantum yield (QY = 76.5%) and thermal stability (82.8%@150 °C) by the traditional solid-state reaction method. The results of XRD and Rietveld refinement show that the presence of Eu3+ ions at Ba2+ sites causes the formation of cation (Zn2+/Ba2+) vacancies in the lattice. The PL and PL decay results reveal that the quenching concentration of BZBO:xEu3+ phosphors is as high as 50%, and the lifetime remains unchanged with Eu3+ concentration due to the unique structure of the host and the cation vacancies generated by the heterovalent substitution. Furthermore, on a 395 nm near-UV chip, a pc-WLED device with exceptional optical performance (CCT = 4415 K, CRI = 92.1) was realized using the prepared BZBO:0.50Eu3+ as a red phosphor. Simple synthesis and excellent performance parameters suggest that the reported BaZnB4O8:xEu3+ phosphors have promising applications in high-power pc-WLEDs. At the same time, it also indicates that cationic vacancy engineering based on heterovalent ion substitution is a potential strategy for improving luminescence quantum yield and thermal quenching performance. [ABSTRACT FROM AUTHOR]

A layered rhombohedral polymorph of indium(III) triiodide is synthesized at high pressure and temperature. The unit cell symmetry and approximate dimensions are determined by single crystal X-ray diffraction. Its R3¯ crystal structure, with a = 7.214 Å, and c = 20.47 Å, is refined by the Rietveld method on powder X-ray diffraction data. The crystal structure is based on InI6 octahedra sharing edges to form honeycomb lattice layers, though with considerable stacking defects. Different from ambient pressure InI3, which has a monoclinic molecular structure and a light-yellow color, high pressure InI3 is layered and has an orange color. The band gaps of both the monoclinic and rhombohedral variants of InI3 are estimated from diffuse reflectance measurements. [ABSTRACT FROM AUTHOR]

In this work, a series of BaSrGd4O8:xBi3+ blue phosphors was synthesized employing the high-temperature solid-state method. Phase purity of the samples was verified by X-ray diffraction and Rietveld refinement. Time-resolved photoluminescence spectra revealed the existence of two distinct Bi sites. Subsequent optimization of dopant types and doping levels in the batch led to an almost twofold increase in quantum efficiency. The introduction of Eu3+ into the phosphors facilitated the construction of an energy transfer pathway. As the concentration of Eu3+ was increased, the emission color changed from blue to purple and finally to red. In addition, the thermal stability and potential applications of the phosphors were extensively investigated. Finally, two WLED devices were successfully fabricated with color rendering indices of 96.27 and 92.18, and correlated color temperatures of 5198 and 2475 K. This underscores the prospective application of these phosphors in the field of high-quality warm WLEDs. [ABSTRACT FROM AUTHOR]

Yellow-green emitting phosphors of vanadate Ca5Mg4(VO4)6 (CMV) doped with different concentrations of Ta5+ ions were synthesized by a solid-state reaction method. The formation of single-phase compounds with a garnet structure was verified by X-ray diffraction (XRD), Rietveld refinement calculations and energy-dispersive X-ray spectroscopy. Different luminescence properties of CMV phosphors such as spectral shift, luminescence lifetime, quantum efficiency, color coordinates and Stokes shift were measured and have been discussed in detail. PLE and PL spectra showed that CMV : xTa5+ (0 ≤ x ≤ 5%) phosphors could match well to 365 nm LED chips, and showed bright yellow-green emission in the visible range of 400–750 nm, with a peak at 544 nm, which is attributed to the charge transfer (CT) of an electron from the 2p orbital of the oxygen atom to the vacant 3d orbital of V5+ ions in the tetrahedral [VO4]3− group. Compared with the CMV host, the integrated luminescence intensity of CMV : 0.5%Ta5+ increased by 26.31%, and the quantum efficiency increased by 15.98%. The phenomenon can be ascribed to the substitution of V5+ ions by the large Ta5+ ions, which resulted in the squeezed and distorted VO4 tetrahedron. Finally, the white light emitting diode (WLED) devices prepared with UV WLED chips and the CMV : 0.5%Ta5+ phosphor exhibited excellent color temperature (4083 K) and CIE coordinates (0.3677, 0.3409). The CMV : 0.5%Ta5+ phosphor can be considered as a potential yellow-green emitting phosphor in the solid-state lighting field. [ABSTRACT FROM AUTHOR]

Pure micro- and nanocrystalline powders of the layered-kagome zinc orthovanadate BaZn3(VO4)2(OH)2 have been successfully prepared and thoroughly characterised. Microstructured samples (BaZn3-MPs) have been produced by hydrothermal reaction using synthetic martyite Zn3V2O7(OH)2·2H2O as the starting reagent. Nanoparticles (NPs) with an average size of ≈ 60 nm (BaZn3-NPs-7h) or ≈ 50 nm (BaZn3-NPs-25min) have been obtained by using a coprecipitation method at ambient pressure, and by varying the stirring time. Rietveld refinements of X-ray diffraction data indicate that micro- and nanostructured BaZn3(VO4)2(OH)2 both crystallize in a Rm structure very similar to that of the known layered-kagome compound BaCo3(VO4)2(OH)2. Transmission electron microscopy observation of BaZn3-NPs-7h and BaZn3-NPs-25min reveals crystallized NPs with homogenous distributions of Ba, Zn, and V elements. FT-IR and Raman spectra show subtle differences between micro- and nanostructured samples which cannot be linked to any differences in the average crystal structures. The high resolution 51V MAS NMR spectrum of BaZn3-MPs shows a single isotropic line attributed to VO43− groups with C3v point group. The spectra of the nanostructured samples reveal the presence of a weak additional signal which decreases in intensity with increasing the NPs size, and which has been tentatively assigned to the presence at the surface of the NPs of a small amount of V5+ ions in a different chemical environment. Nanostructuring also impacts the optical properties of BaZn3(VO4)2(OH)2. The UV-vis absorption spectra of NPs exhibit an additional weak transition in the visible domain which is not observed for the microstructured sample. [ABSTRACT FROM AUTHOR]

Zn1−xCoxMn1−xFexCrO4 ferrichromate was synthesized using the sol–gel auto-combustion method. Rietveld refinement confirms a single phase simple cubic spinel structure in all the samples. FESEM images indicated mixed morphology for all the samples with nearly hexagonal/spherical shape and the agglomeration of particles. The elemental composition was confirmed using EDAX analysis. To validate the morphology of Zn1−xCoxMn1−xFexCrO4 ferrichromate obtained through FESEM, TEM images were taken, and the TEM images were in accordance with the FESEM images. Different oxidation states of Zn1−xCoxMn1−xFexCrO4 (X = 1.0) ferrichromate was determined using XPS. The surface area of Zn1−xCoxMn1−xFexCrO4 ferrichromate was determined using BET analyzer. Further, the electrical conductivity of all the samples were investigated, and the correlation between the surface area and conductivity were discussed. The as-synthesized Zn1−xCoxMn1−xFexCrO4 ferrichromate materials were tested for their electrochemical and supercapacitor applications. The electrochemical measurements revealed that Zn1−xCoxMn1−xFexCrO4 with concentration (X = 1.00) exhibits superior electrochemical performance over the other samples. A high specific capacitance of 286.94 F g−1 and high energy density of 14.30 W h kg−1 at a scan rate of 10 mV s−1 and 93.4% capacity retention over 5000 cycles were observed for Zn1−xCoxMn1−xFexCrO4 (X = 1.00) ferrichromate. These properties make Co1.0Fe1.0Cr1.0O4 ferrichromate an excellent electrode material to study supercapacitor applications. [ABSTRACT FROM AUTHOR]

Extensive research has gone into modifying the chemical composition of phosphors to achieve desirable optical properties. Here, oxynitride phosphors K2Ba6.72Si16O40−1.5yNy:0.28Eu2+ were synthesized by introducing N3− (y) into a K2Ba6.72Si16O40:0.28Eu2+ lattice. An uneven shrinking of the cell parameters a, b, and c was observed through a combination of X-ray diffraction studies and Rietveld refinements. This shrinking caused a large centroid shift (εc) and splitting of the 5d energy level (εcfs), thus inducing the broadening of the excitation spectra (104 → 127 nm, y = 0 → y = 12) and the red shift of the emission spectra (501 → 543 nm, y = 0 → y = 12). The modified series of samples have a broad excitation spectrum, suitable of use in UV, near-UV, and blue light-emitting LEDs. In addition, the optimal sample, K2Ba6.72Si16O31N6:0.28Eu2+, benefits from an increased activation energy and thermal stability. [ABSTRACT FROM AUTHOR]

The new compound Ba6Si2Se12 was synthesized, and the crystal structure and physical properties are reported here. Ba6Si2Se12 adopts a new structure type in the triclinic P1¯ space group with the lattice parameters a = 9.1822(7) Å, b = 12.2633(14) Å, c = 12.3636(18) Å, α = 109.277(3)°, β = 104.734(2)°, and γ = 100.4067(16)°. Notably, the structure features disordered Se22− dumbbells that have also been observed in the germanium selenide with the analogous stoichiometry (Ba6Ge2Se12). Density functional theory calculations revealed that Ba6Si2Se12 is a semiconductor with a calculated band gap of 1.74 eV. UV/vis/NIR absorption spectra indicated that the experimental band gap of Ba6Si2Se12 is 1.89 eV. While exploring this compound's phase width, it was discovered that up to 75% of the Si could be substituted with Ge while retaining the structure type. Rietveld refinements were performed on the phase-pure samples of Ba6Si2−xGexSe12 (x = 0, 0.5, 1, and 1.5) using data collected at the Canadian Light Source's High Energy Wiggler Beamline. The cell parameters, Si/Ge occupancies, and disordered Se22− occupancies were studied. Raman spectra displayed the expected Si–Se and Ge–Se stretching modes from 215 cm−1 to 280 cm−1. The samples were also hot-pressed into pellets to determine their thermal conductivity values ranging from 0.5 to 0.4 W m−1 K−1 for the x = 0, 0.5, and 1.5 samples. The x = 1 sample stood out with a remarkably low thermal conductivity of 0.3 W m−1 K−1, consistent from room temperature up to 573 K. [ABSTRACT FROM AUTHOR]

An organic cation lacking specificity in its structure-directing action offers the possibility, through the screening of other structure-directing parameters, to synthesize a variety of zeolites. In this work we show that the organic structure-directing agent 2-isopropyl-1,3-dimethylimidazolium (2iPr13DMI) can produce up to seven different zeolite phases depending on water concentration, the presence of inorganic impurities, crystallization temperature and time, and germanium molar fraction. The obtained phases are very different in terms of pore system, connectivity of the zeolite structure and structural units. At the pure SiO2 side, ZSM-12 and SSZ-35 dominate, with ZSM-12 being favored by the presence of potassium impurities and by less concentrated conditions. The introduction of Ge at low levels favors SSZ-35 over ZSM-12 and as the Ge fraction increases it successively affords CSV, -CLO and two distinct UOS zeolites, HPM-11 and HPM-6. These two zeolites have the same topology but distinct chemical compositions and display powder X-ray diffraction patterns that are much different from each other and from that of as-synthesized IM-16 (UOS reference material). They also show different symmetry at 96 K. Rietveld refinements of the three as-made UOS materials mentioned are provided. HPM-6 and HPM-11 are produced in distinct, non-adjacent crystallization fields. The frequent cocrystallization of the chiral STW zeolite, however, did not afford its synthesis as a pure phase. Molecular mechanics simulations of the location of the organic cation and host–guest interactions fail to explain the observed trends, but also considering the intrinsic stability of the zeolites and the effect of germanium help to rationalize the results. The study is completed by DFT calculations of the NMR chemical shifts of 13C in UOS (helping to understand splittings in the spectrum) and 19F in CSV (supporting the location of fluoride inside the new [4452], which is an incomplete double 4-ring). [ABSTRACT FROM AUTHOR]

The crystal structure of YbSbO4 was determined from powder X-ray diffraction data using the Rietveld method. YbSbO4 is found to be monoclinic and isostructural to α-PrSbO4. We have also tested the influence of pressure on the crystal structure up to 22 GPa by synchrotron powder X-ray diffraction. No phase transition was found. The P–V equation of state and axial compressibilities were determined. Experiments were combined with density-functional theory calculations, which provided information on the elastic constants and the influence of pressure in the crystal structure and Raman/infrared phonons. Results are compared with those from other orthoantimonates. Reasons for the difference in the high-pressure behaviour of YbSbO4 compared with most antimony oxides will be discussed. [ABSTRACT FROM AUTHOR]

The recent discovery of an innovative chemical vapour synthesis (CVS) approach for the encapsulation and stabilization of high-spin ferromagnetic γ-Fe nanocrystals inside carbon nano-onions (CNOs) has attracted significant attention. Stabilization of the γ-phase of iron is of particular interest for possible applications in self-regulating hyperthermic dissipative systems, under specific conditions of magnetic tuning. Here, we explore a further modification of the synthesis method, by adding controlled quantities of nickelocene into mixtures of ferrocene, dichlorobenzene and sulfur. In these experiments, sulfur plays a crucial role in stabilizing the face centred cubic (FCC) γ-FeNi phase, up to relative abundances of 94%. The structural and magnetic properties were investigated by employing SEM, TEM, HRTEM, XRD, Rietveld refinements, temperature dependent SQUID magnetometry and T-ESR. The presence of a transition from a high-temperature ferromagnetic state at TC1 ~ 400 K to a low-temperature disordered frozen magnetic state at TC2 ~ 60 K is further discussed. [ABSTRACT FROM AUTHOR]

Exploring the functionalities of materials requires a profound understanding of the crystal structure. In this paper, room temperature crystal structures of a new solid solution (1 − x)Ba(Cu1/3Nb2/3)O3-(x)PbTiO3 have been investigated in the entire compositional span and different crystallographic phases and phase coexistence regions have been discovered. The confirmation of the symmetry of these crystal structures has been done with the help of Rietveld analysis of the high-resolution XRD data. Despite both the end components, Ba(Cu1/3Nb2/3)O3 and PbTiO3, having tetragonal (P4mm) symmetry, new cubic and monoclinic phases have been discovered for the intermediate compositions with multiple phase boundaries. The composition region 0.05 ≤ x ≤ 0.55 exhibits a cubic crystal structure and increasing PbTiO3 concentration to 0.62 results in a unique coexistence of two tetragonal phases with different tetragonalities. This transformation is mediated by coexisting cubic and tetragonal phases, for 0.59 and 0.60. The crystal structure of the solid solution later transforms into coexisting monoclinic and tetragonal phases for a wider compositional span i.e., 0.65 ≤ x ≤ 0.85. This composition region is very fascinating, as two phenomenologically different monoclinic structures have been observed in it. Finally, a tetragonal phase at x = 1 is achieved through the mediation of two coexisting tetragonal phases, for the region 0.85 < x ≤ 0.975. The evolution of different crystallographic structures and the coexisting phases are critically comprehended using the variations in the lattice parameters and unit cell volume. The presence of multiple phase boundaries spread across a wide range of compositions makes this solid solution very intriguing and a viable choice for exploring different properties with compositional tuning. [ABSTRACT FROM AUTHOR]

The effects of composition and preparation conditions of palmierite-type K5Yb1−xEux(MoO4)4 (KYEMO) compounds on their structural and luminescence properties were studied in this work. The solid solutions were obtained in three ways: 1) annealing at 893 ± 10 K (low-temperature (LT) phases); 2) slow cooling to room temperature from 1123 ± 10 K (intermediate (IM) phases); 3) quenching in liquid nitrogen from 1123 ± 10 K (high temperature (HT) phases). As a result, three modifications, α-phase (space group (SG) R3¯m), β-phase (superspace group (SSG) C2/m(0β0)00 or X2/m(0β0)00), and γ-phase (SG C2/c) were obtained and characterized. The regions of existence of various modifications of the solid solutions were established. α-KYEMO (0 ≤ x ≤ 1 solid solutions, HT-) and LT- and IM-phases with 0.8 ≤ x ≤ 1 have trigonal symmetry (SG R3¯m). The LT- and IM-phases with 0.3 ≤ x < 0.8 have monoclinic symmetry (SG C2/m). The incommensurately modulated structure of β-K5Yb0.3Eu0.7(MoO4)4 was refined from synchrotron XRD data by the Rietveld method in the superspace group C2/m(0β0). The luminescence characteristics of the series of KYEMO solid solutions were studied. The influence of the Eu3+ concentration on the PL spectra of α-KYEMO under excitation at the 7F0 → 5L6 Eu3+ transition (λex = 395 nm) and CTB (λex = 260 nm) and the influence of synthesis conditions on the luminescence intensities of Eu3+ and Yb3+ emission were investigated. Increasing the concentration of Eu3+ shifts the CIE coordinates from an orange to an orange-red region. The synthesis method, composition and structure affect the color change from light orange to orange in the order HT → LT → IM for x = 0.5 and LT → HT → IM for x = 0.8. Periodic (γ-phase) and aperiodic (β-phase) ordering of K1 and Yb in M1 positions in the structure is more preferable for the emission of 2F5/2 → 2F7/2 transition of Yb3+ ions than a random distribution of the cations in the α-phase structure. The 5D0 → 7F0 and 5D0 → 7F2 Eu3+ transition intensities and the Eu3+/Yb3+ emission ratio depend on the excitation. From the PLE spectra for β-KYMO, the optical band gap was determined to be 4.13 eV. The quantum yield measured for α-K5Yb0.3Eu0.7(MoO4)4 has a very high value of 62%. The intensities of Eu3+ and Yb3+ emission depend on the Eu3+/Yb3+ ratio as well as the excitation wavelength. The structural and optoelectronic characteristics make the K5Yb1−xEux(MoO4)4 phosphors strong contenders for near UV-WLEDs. [ABSTRACT FROM AUTHOR]

Two new families of zinc/cobalt/aluminum-based pigments, with a unique composition, were obtained through the polyol method. The hydrolysis process of a mixture of Co(CH3COO)2, Zn(acac)2 and Al(acac)3 (acac− = acetylacetonate ion) in 1,4-butanediol afforded dark blue gels (wPZnxCo1−xAl), in the presence of a supplementary amount of water, and light green powders (PZnxCo1−xAl), respectively, for the water-free procedure (x = 0, 0.2, 0.4). The calcination of the precursors yielded dark green (wZnxCo1−xAl) and blue (ZnxCo1−xAl) products. XRD measurements and Rietveld refinement indicate the co-existence of three spinel phases, in different proportions: ZnxCo1−xAl2O4, Co3O4 and the defect spinel, γ-Al2.67O4. The Raman scattering and XPS spectra are in agreement with the compositions of the samples. The morphology of wZnxCo1−xAl consists of large and irregular spherical particle aggregates (ca. 5–100 mm). Smaller agglomerates (ca. 1–5 mm) with a unique silkworm cocoon-like hierarchical morphology composed of cobalt aluminate cores covered with flake-like alumina shells are formed for ZnxCo1−xAl. TEM and HR-TEM analyses revealed the formation of crystalline, polyhedral particles of 7–43 nm sizes for wZnxCo1−xAl , while for ZnxCo1−xAl , a duplex-type morphology, with small (7–13 nm) and larger (30–40 nm) particles, was found. BET assessment showed that both series of oxides are mesoporous materials, with different pore structures, with the water-free samples exhibiting the largest surface areas due, most likely, to the high percent of aluminum oxide. A chemical mechanism is proposed to highlight the role of the water amount and the nature of the starting compounds in the hydrolysis reaction products and, further, in the morpho-structural features and composition of the resulting spinel oxides. The CIE L*a*b* and C* colorimetric parameters indicate that the pigments are bright, with a moderate degree of luminosity, presenting an outstanding high blueness. [ABSTRACT FROM AUTHOR]

Na2Co1−xFexSiO4 (NCFS)-based ceramics are some of the most promising alternatives to sodium-ion rechargeable batteries (SIBs). It was believed that the intrinsic qualities would be improved by the defect chemistry and the doping impact of iron in Na2CoSiO4 (NCS). In this study, Na2Co1−xFexSiO4 with x = 0.1 and 0.2 sample structural characteristics, optical properties, ionic conductivities, and Na migration are examined. Contrary to the space group Pna21 undoped compound, the Rietveld refinement of the XRD patterns of NCFSs reveals an orthorhombic phase with the space group Pca21. It is discovered that the temperature dependence relaxation obeys the Arrhenius law, and the identical relaxation times for the charge transport mechanism are suggested by the weak separation of the activation energies for the two relaxation processes (R(A) and R(B)). The transportation behavior of Na+ in many chemical environments is made more favorable by Fe doping, and this has a significant impact on the electrical characteristics. As the Fe content increases, the conductivity increases as well. As the frequency increases, the frequency dependence of ac conductivity is examined to identify the conduction mechanisms such as OLPT, CBH, and inverse OLPT models. [ABSTRACT FROM AUTHOR]

Na2Co1−xFexSiO4 (NCFS)-based ceramics are some of the most promising alternatives to sodium-ion rechargeable batteries (SIBs). It was believed that the intrinsic qualities would be improved by the defect chemistry and the doping impact of iron in Na2CoSiO4 (NCS). In this study, Na2Co1−xFexSiO4 with x = 0.1 and 0.2 sample structural characteristics, optical properties, ionic conductivities, and Na migration are examined. Contrary to the space group Pna21 undoped compound, the Rietveld refinement of the XRD patterns of NCFSs reveals an orthorhombic phase with the space group Pca21. It is discovered that the temperature dependence relaxation obeys the Arrhenius law, and the identical relaxation times for the charge transport mechanism are suggested by the weak separation of the activation energies for the two relaxation processes (R(A) and R(B)). The transportation behavior of Na+ in many chemical environments is made more favorable by Fe doping, and this has a significant impact on the electrical characteristics. As the Fe content increases, the conductivity increases as well. As the frequency increases, the frequency dependence of ac conductivity is examined to identify the conduction mechanisms such as OLPT, CBH, and inverse OLPT models. [ABSTRACT FROM AUTHOR]

The Ruddlesden–Popper (RP) oxides in a high grade of purity are generally prepared at high temperature and that is why there are few reports on their nanocrystalline state. These oxides may show good photocatalytic activity in nanocrystalline form because of higher surface area and better morphology. In this context, we are reporting rare earth doped nanocrystalline RP phases LnSrFe0.5Co0.5O4 (Ln = La, Nd, Sm, Gd), which are highly efficient in removing hazardous organic dye pollutants from wastewater both in unitary and ternary solutions. The impact of rare earth ion doping on the structural, magnetic, and optical characteristics of LnSrFe0.5Co0.5O4 has also been comprehensively investigated via different characterization methods. The Rietveld refinement analysis confirmed the formation of single-phase samples having tetragonal symmetry that crystallised in the I4/mmm space group. The refinement results revealed that with heavier rare earth ion doping, there was a continuous decrease in the value of the unit cell parameters and the cell volume. Dominant anti-ferromagnetic (AFM) interactions were seen in each of these compounds, along with the presence of weak ferromagnetic (FM) interactions due to the co-existence of the super-exchange (Co3+–O–Fe3+) FM and (Co3+–O–Co3+, Fe3+–O–Fe3+) AFM interactions. The band gap values of all these nanophases lie in the range of 1.53–1.62 eV, making them suitable photocatalysts for dye degradation. The photocatalytic activity of the synthesised nanophases was assessed using cationic (methylene blue and rhodamine B) and anionic (methyl orange) pollutants as well as their mixture. It has been observed that the Nd-doped catalyst showed better deterioration efficacy for rhodamine B dye, i.e., 99% in 40 min, followed by 84%, 87%, and 85% for the La, Sm, and Gd phases in the same time period, respectively. The results of photocatalytic activity have been interpreted on the basis of bandgap energy values and photoluminescence (PL) intensity. [ABSTRACT FROM AUTHOR]

YbFe2O4-type layered oxides have attracted tremendous interest because the unique crystal comprises two distinct geometrically frustrated triangular cation-sublattices. Herein, a series of YbFe2O4-type materials In2Zn3−xCoxGeO8 (0 ≤ x ≤ 3) were rationally designed and experimentally synthesized for the first time. The crystal structures of In2Zn3−xCoxGeO8 were investigated comprehensively by Rietveld refinements against high-resolution monochromatic Cu Kα1 XRD data. Zn2+, Co2+, and Ge4+ cations are distributed randomly on the [MO]2 bilayer and possess a trigonal bipyramid (TBP) coordination geometry. Because Co2+ has an unpaired electron in the dz2 orbital and a larger electronegativity than Zn2+, Co2+-to-Zn2+ equivalent substitution in In2Zn3−xCoxGeO8 results in more compact MO5-TBPs, which is the origin of anisotropic lattice expansion and contraction along the a and c axes, respectively. The Co2+ moments in the [MO]2 bilayer are strongly AFM coupled and geometrically frustrated, therefore resulting in a spin-glass magnetic transition at around Tg = 20 K for In2ZnCo2GeO8, while a long-range AFM ordering is established for In2Co3GeO8 with a Néel temperature of 53 K, attributed to the significantly enhanced AFM interactions and increased In3+/Co2+ anti-site disordering, as compared to those in In2ZnCo2GeO8. [ABSTRACT FROM AUTHOR]

In the context of the strain-engineering of crystals, the recent observation of the 'strain–intensity' relationship holds an interesting premise for NIR-upconverting (UC) crystals involving a symmetry perturbing agent such as Li+. In this article, we aimed to examine whether the hypothesis for the 'strain–intensity' relationship can be applied in a general manner, i.e., irrespective of the chemical nature of the symmetry-perturbing alkali metal ion. We used the synchrotron X-ray diffraction (SXRD) experiments for an in-depth structural analysis on a series of β-NaYF4:Yb3+/Ho3+-based UC crystals doped with increasing mol% of K+. Subsequent Rietveld analysis confirmed the formation of predominantly β-phase belonging to the P6¯ space group up to a certain dopant mol% of K+ ion. The compressive-lattice strain, as computed from the SXRD data using the Williamson–Hall method, demonstrated a near-proportional relationship with the UC photoluminescence intensity under increasing K+ mol% within the P6¯ phase. Such coherence could not be explained from the crystal morphologies or average structural traits, as obtained from TEM and Rietveld analysis. However, the EXAFS study revealed a possible existence of variation in the local structure in the same samples. To some extent, the observed 'strain–intensity' correlation was manifested in the electron density maps, reflective of the electronic imbalance across the P6¯ samples. We found that even when a bigger alkali metal ion, such as K+ (1.33 Å), gets incorporated within a P6¯ phase as a dopant; it occupies both the lattice position and interstitial voids and influences the resulting lattice strain via the perturbation of local symmetry just like a much smaller Li+ ion (0.60 Å) does. Such findings portray that the connection between the alkali metal ion-induced symmetry perturbation and generated lattice strain is fundamental in nature. [ABSTRACT FROM AUTHOR]

Na2MgScF7 (NMSF) was experimentally obtained for the first time by combining hydrothermal and high-temperature solid-state reactions. X-ray powder diffraction (XRD) combined with Rietveld refinement confirms that NMSF is crystallized in the space group Imma with the cell parameters a = 10.40860(18), b = 7.32804(12) and c = 7.52879(11) Å, α = β = γ = 90° and V = 574.256(24) Å3. Through doping with Tb3+ or Eu3+ ions, downshifting yellow-green or red emission could be achieved in NMSF-based phosphors, respectively. Upconversion emission could also be designed by doping with Yb3+–Er3+, Yb3+–Tm3+, Yb3+–Ho3+ or Er3+. Moreover, the NMSF:Er3+ phosphor exhibited green upconversion emission upon excitation at 980 nm, and it exhibited red emission upon excitation at 1532 nm. Finally, recognizable patterns were obtained under excitation at 254, 365 and 980 nm, indicating that the as-prepared phosphors can be applied to multicolor anti-counterfeiting. Moreover, our synthesis strategy opens up new avenues for the synthesis of novel fluorides. [ABSTRACT FROM AUTHOR]

Mixed electronic and oxide ionic conduction was enabled in digermanate-type La2−xCaxGe2O7−x/2 containing Ge3O10 chains and isolated GeO4 units by substitution of La3+ with Ca2+. The structure and solid solution limit of Ca doped La2Ge2O7 were studied by systematic experiments, including rotation electron diffraction (RED), X-ray diffraction (XRD) and neutron powder diffraction (NPD) experiments, etc. The preferred occupation of Ca2+ and oxygen vacancies was investigated by Rietveld analysis of the NPD data. The obtained conducting material La1.925Ca0.075Ge2O6.963 exhibits superior thermal stability and an order of magnitude improvement in conductivity compared to the parent La2Ge2O7 (∼9 × 10−5 S cm−1 at 1000 °C). BVEL calculations reveal that the oxygen vacancies were stabilized and transported within the framework of La2Ge2O7 by sharing oxygen and oxygen exchange between the adjacent Ge3O10 chains and GeO4 units, exhibiting a three-dimensional oxide ion transport nature. [ABSTRACT FROM AUTHOR]

Mixed electronic and oxide ionic conduction was enabled in digermanate-type La2−xCaxGe2O7−x/2 containing Ge3O10 chains and isolated GeO4 units by substitution of La3+ with Ca2+. The structure and solid solution limit of Ca doped La2Ge2O7 were studied by systematic experiments, including rotation electron diffraction (RED), X-ray diffraction (XRD) and neutron powder diffraction (NPD) experiments, etc. The preferred occupation of Ca2+ and oxygen vacancies was investigated by Rietveld analysis of the NPD data. The obtained conducting material La1.925Ca0.075Ge2O6.963 exhibits superior thermal stability and an order of magnitude improvement in conductivity compared to the parent La2Ge2O7 (∼9 × 10−5 S cm−1 at 1000 °C). BVEL calculations reveal that the oxygen vacancies were stabilized and transported within the framework of La2Ge2O7 by sharing oxygen and oxygen exchange between the adjacent Ge3O10 chains and GeO4 units, exhibiting a three-dimensional oxide ion transport nature. [ABSTRACT FROM AUTHOR]

In this work, a series of Eu3+ doped double perovskite phosphors Ba9La2W4O24:xEu3+ (0.2 ≤ x ≤ 1.0) were synthesized by a high temperature solid-state method. The phase purity and morphology features of phosphors were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rietveld refinement was also executed and the results indicated that the cation site could provide a relative symmetrical environment, which will induce a large orange/red emission ratio. When excited by n-UV light, the phosphors could emit bright orange-red light with the strongest peak at 592 nm corresponding to the 5D0–7F1 transition. The optimal doping concentration of Eu3+ ions was x = 0.8 and the photoluminescence quantum yield could reach 82.9%. The concentration quenching effect was calculated to be dominated by the dipole–dipole interaction and transient spectrum results also gave direct evidence of the concentration quenching. At the operating temperature of the LED (145 °C), the photoluminescence emission intensity can still reach 97.16% at room temperature. The abnormal thermal quenching behavior was demonstrated to be compensated by electrons captured by traps. The satisfactory CIE coordinates, high color purity and strong emission intensity indicated that BLWO:0.8Eu3+ was a potential red phosphor for WLEDs with broad application prospects. [ABSTRACT FROM AUTHOR]

In this study, we utilized the solvothermal synthesis method to engender Zn vacancies on spinel ZnCo2O4 microspheres (VZn-ZCO), intending to improve their electrochemical performance. X-ray photoelectron spectroscopy was used to quantify the Zn vacancies, and this was supported by Rietveld refinement using X-ray diffraction data and energy-dispersive X-ray analysis. The resulting VZn-ZCO material had a high specific area of 53.60 m2 g−1 and an average pore diameter of 7.96 nm, which facilitated faster transport paths and greater surface area for rapid charge transfer. In terms of supercapacitor performance, the VZn-ZCO electrode exhibited battery-type behavior and achieved a high specific capacity of 367 C g−1 at 1 A g−1, as well as excellent rate capability with 82% of capacity retention. Furthermore, it displayed superior cycling stability with 76% retention of the maximum specific capacity after 5000 cycles. Therefore, our findings suggest that producing cationic vacancies is an effective strategy for improving the electrochemical performance of spinels. [ABSTRACT FROM AUTHOR]

To enhance the working quality of WLEDs, considerable efforts have been made to upgrade the thermal quenching resistance of existing phosphors or design new anti-thermal quenching (ATQ) phosphors. Developing a new phosphate matrix material with special structural features has great importance for the fabrication of ATQ phosphors. By phase relationship and composition analysis, we have prepared a novel compound Ca3.6In3.6(PO4)6 (CIP). Coupling ab initio and Rietveld refinement techniques, the novel structure of CIP with partly vacant cationic positions was solved. Taking this unique compound as the host and using the inequivalent substitution of Dy3+ for Ca2+, a series of C1−xIP:Dy3+ rice-white emitting phosphors were successfully developed. When the temperature was raised to 423 K, the emission intensity of C1−xIP:xDy3+ (x = 0.01, 0.03, and 0.05) increased to 103.8%, 108.2%, and 104.5% of the original intensity at 298 K, respectively. Except for the strong bonding network and inherent cationic vacancy in the lattice, the ATQ property of the C1−xIP:Dy3+ phosphors is mainly attributed to the generation of interstitial oxygen from the substitution of unequal ions, which releases electrons with the thermal stimulus, causing anomalous emission. Finally, we have explored the quantum efficiency of C1−xIP:0.03Dy3+ phosphor and the working performance of PC-WLED prepared with C1−xIP:0.03Dy3+ phosphor and 365 nm chip. The research work sheds light on the relationship between lattice defects and thermal stability, and meanwhile offers a new strategy for the development of ATQ phosphors. [ABSTRACT FROM AUTHOR]

To enhance the working quality of WLEDs, considerable efforts have been made to upgrade the thermal quenching resistance of existing phosphors or design new anti-thermal quenching (ATQ) phosphors. Developing a new phosphate matrix material with special structural features has great importance for the fabrication of ATQ phosphors. By phase relationship and composition analysis, we have prepared a novel compound Ca3.6In3.6(PO4)6 (CIP). Coupling ab initio and Rietveld refinement techniques, the novel structure of CIP with partly vacant cationic positions was solved. Taking this unique compound as the host and using the inequivalent substitution of Dy3+ for Ca2+, a series of C1−xIP:Dy3+ rice-white emitting phosphors were successfully developed. When the temperature was raised to 423 K, the emission intensity of C1−xIP:xDy3+ (x = 0.01, 0.03, and 0.05) increased to 103.8%, 108.2%, and 104.5% of the original intensity at 298 K, respectively. Except for the strong bonding network and inherent cationic vacancy in the lattice, the ATQ property of the C1−xIP:Dy3+ phosphors is mainly attributed to the generation of interstitial oxygen from the substitution of unequal ions, which releases electrons with the thermal stimulus, causing anomalous emission. Finally, we have explored the quantum efficiency of C1−xIP:0.03Dy3+ phosphor and the working performance of PC-WLED prepared with C1−xIP:0.03Dy3+ phosphor and 365 nm chip. The research work sheds light on the relationship between lattice defects and thermal stability, and meanwhile offers a new strategy for the development of ATQ phosphors. [ABSTRACT FROM AUTHOR]

The reasonable modification of layered cathode materials and simple modulation of aqueous electrolytes have both been identified as effective strategies to expedite reaction kinetics, improve zinc storage capacity and maintain structural stability. Herein, (2-M-AQ)-VO nanobelts, formulated as (2-M-AQ)0.1V2O5·0.4H2O (2-M-AQ = 2-methylanthraquinone) with rich oxygen vacancies were obtained via a facile one-step solvothermal technique. Rietveld refinement demonstrated the successful intercalation of 2-M-AQ in the layered V2O5 with a large interlayer spacing of ∼13.5 Å. (2-M-AQ)-VO showed a good electrochemical performance in 3 M Zn(CF3SO3)2 electrolyte. More importantly, in the electrolyte with Cu2+ additive, it exhibited a superior rate capability and remarkably enhanced long-term cyclability with a capacity retention exceeding 100% over 1000 cycles at 1 A g−1. This is associated with the synergistic effect of cathode modification and anode protection induced by electrolyte modulation. Cu2+ in the electrolyte can enter the interlayer channel of the (2-M-AQ)-VO cathode to act as an auxiliary pillar to maintain its structural integrity and can also promote the insertion of H+ in (2-M-AQ)-VO, leading to a reversible phase conversion on the cathode side and in situ formation of a protective layer on the Zn anode side, as evidenced by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Building on studies of monoclinic Li3SiNO2, a polymorph, β-Li3SiNO2, with a previously unknown structure type was synthesized. The β-phase crystallizes in the orthorhombic space group Pbca (no. 61) with lattice parameters of a = 18.736(2), b = 11.1267(5), c = 5.0897(3) Å, and a cell volume of V = 1057.2(1) Å3. Using high-temperature solid-state reactions in sealed tantalum tubes, it was possible to obtain high purity samples (<5 wt% of side phase LiSi2N3 according to Rietveld analysis) containing exclusively one or the other polymorph, depending solely on the cooling rate. In contrast to the monoclinic phase, orthorhombic β-Li3SiNO2 additionally contains a third layer and shows a layer-sequence of the type ABCB. Doped with the activator ion Eu2+, the new polymorph exhibits an intense yellow emission (λmax = 586 nm, fwhm = 89 nm, 0.33 eV, 2650 cm−1) under irradiation with UV to blue light. Hence, the structural difference between the two polymorphs goes along with a significant blue-shift of 16 nm. The results from single-crystal diffraction and single-grain luminescence measurements were confirmed by Rietveld analysis of bulk samples and powder luminescence data. [ABSTRACT FROM AUTHOR]

Building on studies of monoclinic Li3SiNO2, a polymorph, β-Li3SiNO2, with a previously unknown structure type was synthesized. The β-phase crystallizes in the orthorhombic space group Pbca (no. 61) with lattice parameters of a = 18.736(2), b = 11.1267(5), c = 5.0897(3) Å, and a cell volume of V = 1057.2(1) Å3. Using high-temperature solid-state reactions in sealed tantalum tubes, it was possible to obtain high purity samples (<5 wt% of side phase LiSi2N3 according to Rietveld analysis) containing exclusively one or the other polymorph, depending solely on the cooling rate. In contrast to the monoclinic phase, orthorhombic β-Li3SiNO2 additionally contains a third layer and shows a layer-sequence of the type ABCB. Doped with the activator ion Eu2+, the new polymorph exhibits an intense yellow emission (λmax = 586 nm, fwhm = 89 nm, 0.33 eV, 2650 cm−1) under irradiation with UV to blue light. Hence, the structural difference between the two polymorphs goes along with a significant blue-shift of 16 nm. The results from single-crystal diffraction and single-grain luminescence measurements were confirmed by Rietveld analysis of bulk samples and powder luminescence data. [ABSTRACT FROM AUTHOR]

Microplatelets of the layered-kagome compound BaCo3(VO4)2(OH)2, which is the Co2+ analogue of mineral vesignieite BaCu3(VO4)2(OH)2, have been prepared with very high yield by hydrothermal reaction using synthetic karpenkoite Co3V2O7(OH)2·2H2O as starting reagent. The Rietveld refinement of X-ray diffraction data indicates that Co3V2O7(OH)2·2H2O is isostructural with martyite Zn3V2O7(OH)2·2H2O. Two single-phased samples of microstructured BaCo3(VO4)2(OH)2 have been characterized using powder X-ray diffraction, FT-IR and Raman spectroscopies, thermal analyses, scanning electron microscopy, energy-dispersive X-ray spectroscopy and magnetisation measurements. Their crystallite sizes perpendicular to the c-axis are in the range of 92(3) to 146(6) nm and depend on the synthesis conditions. Results have been compared to those previously obtained for quasi-spherical nanoparticles having a crystallite size of the order of 20 nm, to explore the effect of the crystallite size on the properties of BaCo3(VO4)2(OH)2. This study highlights that the magnetic properties depend on the crystallite sizes only at low temperatures. [ABSTRACT FROM AUTHOR]

We present a comprehensive experimental study of the crystal structure of calcium vanadate (Ca3V2O8) under systematic temperature and pressure conditions. The temperature evolution (4–1173 K) of the Ca3V2O8 structural properties is investigated at ambient pressure. The pressure evolution (0–13.8 GPa) of the Ca3V2O8 structural properties is investigated at ambient temperature. Across all pressures and temperatures used in the present work, the Ca3V2O8 crystal structure was determined by Rietveld refinement of powder X-ray diffraction data. The experimental high-pressure data are also supported by density-functional theory calculations. According to the high-pressure results, Ca3V2O8 undergoes a pressure-induced structural phase transition at a pressure of 9.8(1) GPa from the ambient pressure trigonal structure (space group R3c) to a monoclinic structure (space group Cc). The experimentally determined bulk moduli of the trigonal and monoclinic phases are, respectively, B0 = 69(2) GPa and 105(12) GPa. The trigonal to monoclinic phase transition appears to be prompted by non-hydrostatic conditions. Whilst the trigonal and monoclincic space groups show a group/subgroup relationship, the discontinuity in the volume per formula unit observed at the transition indicates a first order phase transition. According to the high-temperature results, the trigonal Ca3V2O8 structure persists over the entire range of studied temperatures. The pressure-volume equation of state, axial compressibilities, Debye temperature (264(2) K), and thermal expansion coefficients are all determined for the trigonal Ca3V2O8 structure. [ABSTRACT FROM AUTHOR]

Red phosphors often play a crucial role in enhancing the lighting quality of WLEDs. However, it remains difficult to develop a red phosphor that shows high efficiency, outstanding thermal stability, and high color purity. The struggle against "thermal stability" is always an inevitable task for photoluminescent materials. In this work, we propose a method inspired by nonlinear optical materials to synthesize a novel red-emitting pyrophosphate phosphor Cs2MgZn2(P2O7)2:Eu3+. The phase purity and morphology features are clearly investigated using X-ray diffraction and scanning electron microscopy. The emission spectra show that Cs2MgZn2(P2O7)2:20%Eu3+ can emit bright red light with a high color purity (84.68%) under ultraviolet light excitation. Rietveld refinement of the XRD pattern and luminescence kinetics as a function of the Eu3+ doping concentration were used to obtain information about the crystal structure and determine the Eu3+ site occupation preference. In particular, the sample exhibited excellent thermal stability (100%@170 °C) due to zero thermal quenching behavior, and the mechanism is described in detail. The present work provides a new possibility for the research and application of zero-thermal quenching phosphors. In addition, the fabricated WLED device was characterized via its satisfactory CIE coordinates (0.3508, 0.3233), outstanding correlated color temperature (CCT = 4608 K) and strong emission intensity, which demonstrates its potential for application in the field of WLED solid-state lighting. [ABSTRACT FROM AUTHOR]

In the present study we provide the sorption properties of four 8-connected Zr4+ MOFs with the general formula H16[Zr6O16(RNH-BDC)4]·solvent (RNH-BDC2− = 2-alkyl-amine-terephthalate; R = ethyl-, ET-MOF; R = propyl-, PROP-MOF; R = isobutyl-, SBUT-MOF; R = n-butyl, BUT-MOF) towards toxic Cr(VI) and radionuclide-related ReO4− oxoanions. These MOFs represent superior sorbents for the removal of oxoanionic species, in terms of kinetics, sorption isotherms, selectivity and regeneration/reusability. The excellent sorption capability of the MOFs is due to a combination of surface and intra-framework sorption phenomena. The latter process proceeds via replacement of terminal water/hydroxyl ligands from the Zr6 clusters and subsequent binding of oxonanions to the Zr4+ centers, a fact that was proved via Rietveld PXRD analysis for the anion-loaded BUT-MOF. Importantly, BUT-MOF demonstrated an exceptional sorption capacity for Cr2O72− (505 mg g−1) and was further utilized in a sorption column in the form of MOF/calcium alginate beads, displaying remarkable removal efficiency towards industrial (chrome-plating) wastewater. Furthermore, the luminescence Cr(VI) sensing properties of BUT-MOF were explored in detail, presenting high sensitivity (detection limits as low as 9 ppb) and selectivity for these species against various competitive anions. [ABSTRACT FROM AUTHOR]

The compound Li3SiNO2:Eu2+ was synthesized in high temperature solid-state reactions in weld shut tantalum ampules and the crystal structure of Li3SiNO2 has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c (no. 15) with the lattice parameters a = 1049.01(3), b = 1103.42(3), c = 511.86(2) pm, β = 116.14(1)°, and a volume of V = 0.53187(2) nm3. This compound is built up from two different layers, which are arranged alternately along the crystallographic a-axis. The results from single-crystal diffraction were confirmed by the Rietveld analysis of bulk samples. Moreover, Li3SiNO2 could be successfully doped with the activator ion Eu2+ and the luminescence spectroscopy of single-crystals revealed broad band emission at λmax = 601 nm (fwhm = 90 nm). [ABSTRACT FROM AUTHOR]

The compound Li3SiNO2:Eu2+ was synthesized in high temperature solid-state reactions in weld shut tantalum ampules and the crystal structure of Li3SiNO2 has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c (no. 15) with the lattice parameters a = 1049.01(3), b = 1103.42(3), c = 511.86(2) pm, β = 116.14(1)°, and a volume of V = 0.53187(2) nm3. This compound is built up from two different layers, which are arranged alternately along the crystallographic a-axis. The results from single-crystal diffraction were confirmed by the Rietveld analysis of bulk samples. Moreover, Li3SiNO2 could be successfully doped with the activator ion Eu2+ and the luminescence spectroscopy of single-crystals revealed broad band emission at λmax = 601 nm (fwhm = 90 nm). [ABSTRACT FROM AUTHOR]

A novel polymorph of ThB2O5, denoted as β-ThB2O5, was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB2O5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other known polymorph of ThB2O5, denoted α, synthesised herein using a known borax, B2O3–Na2B4O7, high temperature solid method, was found to transform to the β polymorph when exposed to conditions of 4 GPa and ∼900 °C. Compared to the α polymorph, β-ThB2O5 has smaller molar volume by approximately 12%. Exposing a mixture of the α and β polymorphs to HT/HP conditions ex situ further demonstrated the preferred higher-pressure phase being β, with no α phase material being observed via Rietveld refinements against laboratory X-ray powder diffraction (PXRD) measurements. In situ heating PXRD measurements on α-ThB2O5 from RT to 1030 °C indicated that α-ThB2O5 transforms to the β variant at approximately 900 °C via a 1st order mechanism. β-ThB2O5 was found to exist only over a narrow temperature range, decomposing above 1050 °C. Ab initio calculations using density functional theory (DFT) with the Hubbard U parameter indicated, consistent with experimental observations, that β is both the preferred phase at higher temperatures and high pressures. Interestingly, it was found by switching from B2O3–Na2B4O7 to H3BO3–Li2CO3 flux using consistent high temperature solid state conditions for the synthesis of the α variant, β-ThB2O5 could be generated. Comparison of their single crystal measurements showed this was identical to that obtained from HT/HP conditions. [ABSTRACT FROM AUTHOR]