Search

A series of single Ce3+ doped and Ce3+ and Tb3+ co-doped Na2BaCa(PO4)2 (NBCP) phosphors have been synthesized by conventional solid-stated reaction method. The crystal structure, luminescence properties, thermal stability and energy transfer were carefully investigated. The Ce3+ is inferred to substitute the Ba2+ site in NBCP lattice. The color-tunable emission from blue to green is observed by adjusting Tb3+ concentration among NBCP: 0.03Ce3+, yTb3+ phosphors. The energy transfer behavior from Ce3+ to Tb3+ ions is both illustrated by co-doped PL spectra and decay curves. The energy transfer efficiency is as high as 91.5%. The mechanism of energy transfer is resonance type of dipole-dipole transition. In this work, the optimal phosphor exhibits the excellent thermal stability which keeps at 94.9% of that initial value at room temperature when temperature reaches to 150 ˚C. The Ce3+ and Tb3+ co-doped NBCP phosphor is a promising candidate for the application in the general lighting and display fields.

The photoluminescence behavior of luminescent materials with rare earth (RE) ions as a luminescence center not only depends on the element type and chemical valence of RE ions but also on their concentration and occupation in the matrix, sometimes including the interaction of the matrix and RE ions or between different RE ions. Herein, special SrIn2(P2O7)2 phosphate, assembled by monolayer [SrO10]∞ and bilayer [In2P4O14]∞ consisting of InO6 units and P2O7 groups, was selected as the host material, and different cation positions (Sr and In) were substituted by Eu3+. The structure refinement in combination with Judd-Ofelt theory has shed light on the differences of the Eu3+ coordination environment in SrIn2(P2O7)2. The structural rigidity of the In3+ site is better than that of the Sr2+ site, making SrIn1.92(P2O7)2: Eu0.08 superior in thermal stability. The average distance between adjacent Sr2+ ions is larger than that between adjacent In3+ ions, causing the higher quantum efficiency of Sr0.9In2(P2O7)2: Eu0.1. The present work demonstrates that the site occupation of Eu3+ has an important effect on its luminous performance. Importantly, the newly developed Eu3+-doped SrIn2(P2O7)2 phosphors, exhibiting outstanding luminous efficiency, favorable thermal stability, and excellent color purity, are promising red components of phosphor-based light-emitting diodes.

Investigating the phosphors doped with single activators in a single component to realize white-light emission is urgently desired for phosphor-converted white-light-emitting diodes. In this work, on the basis of the chemical unit cosubstitution strategy, the new borophosphate phosphors Ba

To provide a basic guide for the design of Cu–Cr-based alloys, phase equilibrium relations in the Cu–Cr–Ti system have been studied using diffusion triples and typical equilibrated alloys. Based on the results from electron-probe microscopy analysis and x-ray diffraction, isothermal sections of the Cu–Cr–Ti ternary system at 1073 and 973 K were constructed, wherein 9 and 11 three-phase equilibria were determined, respectively. A ternary phase with an approximate composition of (Cu, Cr)4Ti3 was detected and named as τ1. The binary Cu4Ti3 phase does not connect with τ1 in the ternary region. Solid solution phases (Cu, Cr)3Ti2 and τ1 were identified and confirmed in both diffusion triple and alloy samples. The solubility of Cr in Cu3Ti2 extends to 12 at.% at both 1073 and 973 K. (Cu, Cr)3Ti2 and Cu3Ti2 form a continuous solid solution at 1073 K while do not exist as one stable phase at 973 K. In addition, two two-phase regions of Cu4Ti + (Cu, Cr)3Ti2 and Cu4Ti3 + (Cu, Cr)3Ti2 transform to the three-phase regions of Cu4Ti + Cu4Ti3 + (Cu, Cr)3Ti2 as the temperature decreases from 1073 to 973 K.

The development of novel single-component white-emitting phosphors with high thermal stability is essential for improving the illumination quality of white light-emitting diodes. In this work, we synthesized a series of Ce3+, Tb3+, Mn2+ single- and multiple-doped Ca9La(PO4)7 (CLPO) phosphors with β-Ca3(PO4)2-type structure by the simple high-temperature solid-state reaction. The crystallization behavior, crystal structure, surface morphology, photoluminescence performance, decay lifetime and thermal stability were systematically investigated. The PL spectra and decay curves have evidenced the efficient energy transfer from Ce3+ to Tb3+ and from Ce3+ to Mn2+ in the CLPO host, and corresponding energy transfer efficiency reaches 41.8% and 54.1%, respectively. The energy transfer process of Ce3+→Tb3+ and Ce3+→Mn2+ can be deduced to the resonant type via dipole-dipole and dipole-quadrupole interaction mechanism, and corresponding critical distance were determined to be 12.23 and 14.4 A, respectively. Based on the efficient energy transfer, the white light emission can be successfully achieved in the single-component CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ phosphor, which owns CIE chromaticity coordinates of (0.3245, 0.3347), CCT of 5878 K, internal and external quantum efficiency of 84.51% and 69.32%. Especially, compared with the emission intensity at 25 °C, it still remains 98.5% at 150 °C and 92.0% at 300 °C. Based on these results, the single-component white light emission phosphor CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ is a potential candidate for UV-converted white LEDs.

Single-phase white-emission phosphors possess a judicious usage potential in phosphor-converted white-light-emitting diodes (WLEDs). Recently, numerous efforts have been made toward the development of new patterns of white-emitting phosphors that achieve excellent quantum yield, superior thermal stability, and applaudable cost effectiveness of WLEDs. Finding suitable single-component white phosphor hosts to provide an ideal local environment for activators remains urgent. Inspired by the original discovery of the promising host MgIn2(P2O7)2 (MIP) and its structural dependence on alkali-metal cations, we synthesized a brand-new phosphor host, SrIn2(P2O7)2 (SIP), via the traditional solid-state reaction. Its crystal structure was determined using an ab initio analysis and the Rietveld method. It belongs to a monoclinic unit cell with the space group C2/c. Besides, SIP exhibits a special layered three-dimensional framework in which the monolayer [SrO10]∞ was surrounded by a bilayer [In2P4O14]∞ made of the InO6 octahedra and P2O7 groups. A series of pure SIP:Tm3+,Dy3+ phosphors with tunable blue-white-yellow emission were prepared by adjusting the dopant concentration and utilizing the Tm3+-Dy3+ energy transfer. The daylight-white-emitting phosphor SIP:0.01Tm3+,0.04Dy3+ (the correlated color temperature is 4448 K) exhibits an abnormal thermal antiquenching property, and the emission intensity of 423 K reaches 103.7% of the initial value at 300 K. On the basis of the temperature-dependent lattice evolution and microenvironment analysis, the reduction of β and lattice distortion can lead to lower asymmetry of the activators and benefit the compensation of trapped-electron thermal activation. In this work, an integration study was carried out on the crystal structure of the new matrix, the occupation of the luminescent center, the interaction of different activators in the host, and the distortion degree of the local structure for the activators, which is of great practical sense for producing a novel single-matrix white phosphor possessing superior thermal endurance for UV-light-stimulated WLEDs.

The pure Sm3+/Er3+ doped host-sensitized LaNbO4 phosphors were synthesized and characterized. By virtue of the Rietveld Method, crystal structure of LaNbO4:Sm3+/Er3+ were refined, with the occupation of dopants determined. The luminescence properties of Sm3+/Er3+ doped LaNbO4 phosphors were carefully measured and analyzed by diffuse reflectance spectra, ultraviolet and cathodoluminescence (CL). The energy transfer was recognized between host and doped Sm3+/Er3+ ions based on the luminescence spectra and decay lifetimes, which is dominated by electric multipolar interaction. Further, the calculated critical distance is 23.71 and 23.08 A for Sm3+ and Er3+ doped, respectively. Moreover, the temperature sensitivity of Sm3+/Er3+ doped LaNbO4 was evaluated at the temperature ranging from 23 K to 298 K. By adjusting the concentration of Sm3+/Er3+ ions, the emission colors of LaNbO4:Sm3+ and LaNbO4:Er3+ are varied from blue to pink and from blue to cyan. These results indicate that LaNbO4:Sm3+/Er3+ phosphors can be applied in the plasma display panels (PDP) and general lighting.

This paper focused on the crystal structures of two new ternary phases, Ti(Cu,Pt)2 and Ti(Cu,Pt)3, which were studied by X-ray powder diffraction data using Rietveld method. Electron probe microanalysis was used for sample composition examination. Elastic properties of these phases were further measured by nano-indentation, and meanwhile calculated with first-principle (FP) calculations. It is found that the crystal structure of Ti(Cu,Pt)2 is of orthorhombic cell space group Amm2 (No. 38) with structural prototype of VAu2. The resolved structure of Ti(Cu,Pt)3 is of tetragonal AlPt3 type, belonging to the space group P4/mmm (No. 123). The nano-indentation measurement and FP calculations show that the elastic modulus of Ti(Cu,Pt)2 increases firstly then decreases with Pt content, whereas that of Ti(Cu,Pt)3 almost linearly increases with Pt content.

Commercial white LED devices usually suffer from a high color temperature and poor color rendering. Developing a new, efficient, and stable red phosphor is the key to solving this problem. In this work, a series of pure Ca3Y2-xB4O12:xEu3+ (0 < x ≤ 2) samples, including the new and fully transitional borate phosphor Ca3Eu2B4O12 (CEBO), have been successfully prepared by solid-state reaction synthesis. CEBO is isostructural with Ca3Y2B4O12 (CYBO), belonging to the orthorhombic system with space group Pnma (No. 62). Under optimal 393 nm excitation, this borate exhibits a strong red emission, peaking at 615 nm, with high color purity. Interestingly, the luminescence of CEBO is relatively higher than that of CYBO:Eu3+ phosphors. The quantum yield of this non-concentration-quenching phosphor reaches 95.6%. Furthermore, a warm pc-WLED device has been fabricated by mixing as-prepared CEBO powders and commercial BaMgAl10O17:Eu2+ and (Sr, Ba)2SiO4:Eu2+ phosphors, which exhibits a high color rendering index (Ra = 83.7) along with a color temperature of around 3883 K. The present work indicates that this new borate, with outstanding quantum efficiency and favorable thermal stability, can be used as a red phosphor for application in WLEDs.

The development of suitable red phosphors to obtain improved white color stands a good chance to serve in the new generation of white light-emitting diodes. Owing to multi-elements via doping and oxidation of reduced valence state of lanthanide or transition metal ions, most of the reported phosphors usually suffer from complex synthetic processes and unstable color of the lighting industry cycle. In this work, we present a new red emitting and stable Sr3Eu2B4O12 phosphor with regard to its special structure. It crystallizes as an orthorhombic cell, with Sr and Eu atoms co-occupying three different lattice sites in the space group of Pnma (no. 62). It is proposed that the long bond distance between activators minimizes the content quenching, while the high disorder of location restricts the thermal quenching. This phosphor emits bright red light with good color purity under UV excitation, with the luminescence intensity and quantum yield tunable via the fabrication temperature. Through a preliminary optimization of the synthesis process, the Sr3Eu2B4O12 phosphor prepared at 1250 °C has high quantum yields of about 94.7% and excellent thermal stability of 85.6% intensity retention at 150 °C relative to the initial value at room temperature. The calculated Judd–Ofelt intensity parameters (Ω2, Ω4) further clarified that the Eu3+ site in Sr3Eu2B4O12 had lower symmetry without an inversion center, and more distorted local environment and structural rigidity of the host, predicting excellent thermal stability. Finally, a warm pc-WLED device has been produced by mixing as-prepared Sr3Eu2B4O12 powders and commercial BaMgAl10O17:Eu2+ and (Sr, Ba)2SiO4:Eu2+ phosphors, which exhibits a high color rendering index (Ra = 83.4) along with a color temperature at around 4102 K. The present work indicates that the Sr3Eu2B4O12 phosphor is an efficient red component with excellent thermal stability for white-light production of near-UV-excited w-LEDs.

The structure-property relationship of photoelectric functional materials has been recognized as a hot topic. The study of the inner link between the band gaps and birefringence of optical materials is extremely crucial for the design and creation of novel optical devices, but still remains rather unexplored. In this work, taking a series of borates with only planar-triangular BO3 groups, α-/β-TM3(BO3)2 (TM = Zn, Cd), Cd2B2O5, and M3(BO3)2 (M = Hg, Mg, Ca, Sr) as the research subject, the comprehensive relationship between their electronic structures and linear optical properties has been systematically investigated. Through combining experimental measurements and theoretical calculations, the effect of optical polarizability on the birefringence of these borates was clarified. Based on the present discussion, the relationship between the O (2p) bandwidth of the highest valence band and the HSE06 band gaps is opposite. Meanwhile, a method involving the determination of so-called optical permittivity Δe to evaluate the magnitude of birefringence Δn is found to be feasible. A large Δe makes a positive contribution to Δn. In addition, the experimentally measured band gaps and IR vibrations are in good agreement with theoretical results for the compounds α-Cd3(BO3)2 and Cd2B2O5.

The local symmetry of a Eu3+ ion has a crucial effect on its luminescence properties. In this work, we show that the red/orange ratio in the emission of Eu3+-doped MgIn2P4O14 phosphors is tunable by adjusting the Eu3+ concentrations, due to the change in the local symmetry of metal ions. The substitution of Eu3+ for In3+ lowers the distortion in the lattice of monoclinic MgIn2P4O14, and an increase in Eu3+ doping concentration causes the metal ion sites to shift closer to an inverse center, leading to a reversal of the relative emission intensity of a magnetic dipole transition to an electric dipole transition. Meanwhile, the higher asymmetry of metal ion sites occupied by Eu3+ in MgIn2P4O14 makes the luminescence less thermally stable than that in Mg3In4P6O24.

Vanadium pentoxide (V2O5) is an attractive high-capacity cathode material for lithium-ion batteries but is limited by the poor structural stability. In this work, we report the synthesis and properties of a new lithium-ordered superstructure of Li0.0625V2O5 through controlled prelithiation treatment. Compared to VO5 square pyramids in a pure α-V2O5 structure, the distorted VO5 square pyramid in this superstructure imparts an intrinsic layer structure with improved stability, expanded c-plane spacing, as well as expansion in the a-axis. In the voltage range of 2.5–4.0 V vs Li/Li+, Li0.0625V2O5 nanobelts with lithium-ordered superstructures exhibit a specific capacity up to 215 mAh g–1, ultrahigh cycling capability, and high rate capability. Cyclic voltammograms of lithium insertion into Li0.0625V2O5 nanobelts also demonstrate two new pairs of reversible pseudocapacitive peaks in addition to the ordinary peaks of Li+ insertion into the pure orthorhombic α-V2O5.

The photoluminescence behavior of luminescent materials with rare earth (RE) ions as a luminescence center not only depends on the element type and chemical valence of RE ions but also on their concentration and occupation in the matrix, sometimes including the interaction of the matrix and RE ions or between different RE ions. Herein, special SrIn

A new phosphate Ba3In4(PO4)6 has been discovered in the exploration of novel host materials for color-tunable phosphors in BaO-In2O3-P2O5 system. The crystal-structure determination using powder XRD data reveals it belongs to the cubic langbeinite structure type (S.G. P213), unlike Mg3In4(PO4)6 crystallizing the triclinic system (S.G. P 1 ¯ ). The existence of PO4 has been verified by IR spectra of the title compound. DTA and experimental indicate that this new phosphate has a high melting point of ∼1293 °C. Combined with calculated electronic structure and experimental UV-Vis diffuse reflectance spectrum, it has a wide direct energy band gap which is favorable for host materials. The site symmetry of Eu3+ ions and the cross relaxation of Tb3+ ions in this matrix have been clarified according to their luminescence properties. Red-pink-green tunable emission can be realized adjusting the Eu3+ and Tb3+ contents. The quantum yields of representative phosphors under the excitation of 370–392 nm ultraviolet radiation have been measured and discussed. The PL intensity of Ba3In4(PO4)6: 0.02Eu3+, 0.015 Tb3+ phosphor at 423 K of is about 67% of that at 298 K. Present results indicate that the Ba3In4(PO4)6-based phosphors are valuable for the multicolor and stable thermal performance in the display and lighting fields.

Tb-Si intermetallics have been recognized as interesting magnetic and electrical materials. The addition of Cr can modify the property and broaden the application of Tb-Si intermetallic compounds. Understanding phase relations, phase stability and microstructural changes of relative systems are essential for tuning and improving performance of this type of materials. In this work, phase relationships in the Tb-Si-Cr ternary system have been studied based on phase and microstructure identification of key equilibrated alloys. Isothermal sections of this system at 1273 K and 1073 K were experimentally constructed by means of electron probe microanalysis, X-ray diffraction, and differential thermal analysis. As one of results, the ternary compound TbSi2Cr2 was confirmed to exist at both 1273 K and 1073 K. In addition, remarkable solubilities of the third element were detected in some binary compounds. The solubility of Cr in Tb2Si3-δ and TbSi at 1273 K are about 4.0 and 9.1 at%, respectively. The solubility of Cr in Tb5Si3 increases from 3.0 at% at 1273 K to 6.2 at% at 1073 K. Besides, the compound Tb2Si3-δ were determined to be stable ranging from 1098 ± 25 K to 1513 ± 10 K, based on the analysis of microstructure. Moreover, the annealing temperature dependence of micro-hardness for Tb2Si3-δ intermetallic phase was investigated by nano-indentation.

Ni and Zn are important alloying elements in Mg-based structural materials and hydrogen storage alloys. The isothermal section of the Mg-Ni-Zn system at 400 °C was investigated by means of X-ray diffraction (XRD) analysis and electron probe microanalysis (EPMA). The NiZn3 phase was observed to be stable in the as-cast and annealed Ni25Zn75 and Ni23Zn77 alloys. The experimental results confirmed the existence of the ternary τ compound at 400 °C. NiZn3, Mg2Zn3, Mg2Ni, MgZn2, MgNi2, and τ show significant homogeneity ranges in the ternary system. The Mg2Zn11 phase is being stabilized in the ternary system at temperatures higher than the melting point of this compound in the Mg-Zn binary system. In the frameworks of the CALPHAD approach, the Ni-Zn system was re-optimized and the thermodynamic description for the Mg-Ni-Zn system was thermodynamically assessed for the first time. The obtained thermodynamic models reasonably reproduce the experimental data on the phase equilibria and thermodynamic properties of the phases. The solidification paths of the representative Mg-Ni-Zn alloys were predicted within the Scheil-Gulliver model using the thermodynamic assessment performed in the present work. The results of the Scheil-Gulliver modeling are in agreement with the EPMA results.

Sn and Zr are two important alloying elements in low-modulus biomedical titanium alloys, yet experimental data on Sn diffusion in bcc Ti and bcc Zr are still very limited in the literature, and thus were systematically measured in the present study using solid–solid diffusion couples (SSDCs) and novel liquid–solid diffusion couples (LSDCs). Both interdiffusion and impurity diffusion coefficients in the bcc phase of the Ti-Sn and Zr-Sn systems were extracted with forward-simulation analysis (FSA), and show good agreement with existing literature. The interdiffusion coefficients in the Ti-Sn system at six temperatures, from 950 °C to 1200 °C, extend experimental measurements to a much wider composition range, and the interdiffusion coefficients in the Zr-Sn system at 1200 °C, 1150 °C, and 1100 °C are the first such data experimentally measured. The data obtained from this study, together with our previous data for the Ti-X (X = Cr, Hf, Mo, Nb, V, Zr) systems, provide reliable experimental inputs to improve the mobility databases for advanced Ti alloys development. In addition, the excellent agreement between the LSDCs and SSDCs results validates the reliability of this novel approach by combining LSDC experiments and FSA in evaluating diffusion coefficients at elevated temperatures.

Mg2Si1−xSnx-based compounds have been recognized as promising thermoelectric materials owing to their high figure-of-merit ZTs, abundance of raw constituent elements and nontoxicity. However, further improvement in the thermoelectric performance in this type of material is still constrained by the high thermal conductivity. In this work, we prepared a series of representative Mg2Si0.4−xSn0.6Sbx (x = 0, 0.0075, 0.008, 0.009, 0.01, 0.011) samples via the alkaline earth metal reduction method through a combination of ball milling and spark plasma sintering (SPS) processes. The samples featured many dislocations at the grain boundaries and plenty of nanoscale-coherent Mg2Si–Mg2Sn spinodal phases; both of which can effectively scatter heat-carrying phonons and have nearly no impact on the carrier transport. Meanwhile, Sb-doping can efficiently optimize the carrier concentration and significantly suppress the bipolar effects. As a result, a maximal ZT of 1.42 at 723 K and engineering (ZT)eng of 0.7 are achieved at the optimal Sb-doping level of x = 0.01. This result indicates that the alkaline earth metal reduction method could be an effective route to engineer phonon transport and improve the thermoelectric performance in Mg2Si1−xSnx-based materials.

Mn2+ doped γ-AlON is an interesting narrow-band green emitting phosphor which can be used in wide color gamut white LED backlights for liquid crystal displays (LCDs). However, the spin-forbidden transition of 3d5 in Mn2+ results in a quite low absorption efficiency, γ-AlON:Mn2+ thus has a small external quantum efficiency. Besides Eu2+,Ce3+ is another promising sensitizer and is expected to improve the emission of Mn2+ through a distinctive energy transfer process. In this work, a series of Ce3+–Mn2+ codoped γ-AlON phosphors were synthesized by gas pressure sintering at 1800 °C for 2 h under 0.5 MPa nitrogen gas pressure. The Rietveld refinement analysis shows that Al atoms occupy both 8a and 16d sites, while codoped Ce3+ and Mn2+ ions substitute the 8a Al atoms only in the tetrahedral sites. The 27Al solid state NMR spectrum further confirms the chemical shifts of AlO4 and AlO6 sites at 71.4 and 0 ppm, respectively. The measured PL, CL and decay times have evidenced that a brisk energy transfer occurs between the Ce3+ and Mn2+ ions. The energy transfer mechanism from Ce3+ to Mn2+ in γ-AlON is a quadrupole–quadrupole interaction and the critical distance is calculated to be 15.97 A. Upon UV or blue light excitation, the codoped γ-AlON phosphor has higher luminescence intensity, quantum efficiency and thermal stability than the Mn2+-doped γ-AlON due to the energy transfer and low total concentration of Ce3+ and Mn2+ ions. Meanwhile, the absorption, internal quantum efficiency and external quantum efficiency are raised to 60.2%, 61.3% and 36.9% upon 310 nm excitation.

The borate Ba3InB9O18 (BIBO) is a promising host material for phosphors. A series of Tb3+ and Eu3+ codoped Ba3InB9O18 phosphors were synthesized. Based on the Rietveld method, structure refinement of the codoped BIBO phosphor was carried out. Then, the luminescence properties of BIBO:Tb3+, Eu3+ phosphors were extensively investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. The measured PL spectra and decay times evidenced that energy transfer occurs between the Tb3+ and Eu3+ ions. The energy-transfer mechanism from Tb3+ to Eu3+ in Ba3InB9O18 is dominated by electric multipolar interactions, with the critical distance calculated to be 10.97 A. The temperature sensitivity of the Tb3+ and Eu3+ codoped sample under VUV was also investigated at the low temperature range from 25 K to 298 K. The emission color could be tuned from green to the red region by adjusting the concentration of codoped ions. The results indicate that the BIBO-based phosphors are valuable candidates for applications in the display and lighting fields.

Controlling the chemical and physical structure at the atomic level is of paramount importance for decreasing the thermal conductivity by enhancing phonon scattering in thermoelectic materials. Additional enhancement in the figure of merit (ZT) can be achieved by improving the electron transport properties. Cu-deficient ternary I-III-VI compounds receive an increasing attention because they can easily form solid solutions and thereby can readily engineer their own thermoelectric performance. In this work, we present a novel thermoelectric compound Cu1.15In2.29Te4 with the dimensionless figure of merit ZT ~1.0 through alloying with Cu2Te. The enhanced ZT value is mainly attributed to the ultralow lattice thermal conductivity (κL=0.24 WK-1m-1 at 825 K), caused by a pronounced local lattice disorder as a result of the interstitial residing of extra Te. Density Functional Theory based first-principles calculations further elucidate that the creation of the resonant states at Fermi level and impurity levels near the valence band edge have increased the effective mass and carrier concentration: resulting in the improved electrical properties. Moreover, the localized modes of the Te interstitial defect hybridize with the acoustic modes of stoichiometric In, Te and lead to the enhanced scattering of the thermal phonons resulting in the significant low κL. The above findings substantiate that the proper doping of Cu2Te in the newly developed Cu1.15In2.29Te4 compound can effectively manipulate both electron and phonon transport and thereby promises high thermoelectric performance.

Due to the high sensitivity of the unshielded 5d orbit to the host environment, Ce3+ has a wide-spread emission ranging from near ultraviolet to the red light region, making it a favorable choice for being UV-emitting phosphor activator and sensitizer of other co-doped lanthanide ions in luminescent materials. In present work, Ce4+→Ce3+ self-reduction phenomenon in the layered phosphate MgIn2P4O14 was observed. Noting that self-reduction ability is a valuable characteristic of new host materials, a new viewpoint underlying mechanism was put forward. Structure-, composition-, and temperature-dependence of photoluminescence of the new UV-emitting MgIn2P4O14: Cex phosphors were investigated, with the relative mechanism discussed. Moreover, the sensitization of Dy3+ by Ce3+ was observed in Ce3+/Dy3+ co-doped MgIn2P4O14 phosphors. The excitation region of Dy3+ in MgIn2P4O14: CeDy (220–460 nm) is markedly broadened compared to that of the Dy3+ single-doped phosphor (270–460 nm) on account of the Ce3+→Dy3+ energy transfer process. Present work shows that the MgIn2P4O14: CeDy phosphor can be promising phosphor using for fabrication of both light-emitting diodes (LEDs) and fluorescent lamps (FLs).

Single-phase white-emission phosphors possess a judicious usage potential in phosphor-converted white-light-emitting diodes (WLEDs). Recently, numerous efforts have been made toward the development of new patterns of white-emitting phosphors that achieve excellent quantum yield, superior thermal stability, and applaudable cost effectiveness of WLEDs. Finding suitable single-component white phosphor hosts to provide an ideal local environment for activators remains urgent. Inspired by the original discovery of the promising host MgIn

Luminescent materials were of vital importance in the display, lighting, and biomedical fields. Exploration of novel inorganic host materials and groping for novel color-tunable phosphor materials with good thermal stability is still a major challenge for the quality-improvement of FLs and LEDs. In the present work, a new magnesium indium phosphate, Mg3In4P6O24 (MIP), was successfully synthesized by conventional high-temperature solid-state reaction and was structurally characterized by powder X-ray diffraction analysis, in which magnesium and indium atoms co-occupy four metal cation sites, coordinating with adjacent oxygen atoms forming distorted MO5 and MO6 polyhedra. The VUV-UV excited luminescence properties of a series of Eu3+/Tb3+ doped MIP phosphors were investigated, with the temperature-dependence of photoluminescence and relative mechanism analyzed. Under the excitation of 254 nm, the MIP: EuxTby phosphors can generate bright color-tunable green-yellow-red light by changing the doping concentration. In addition, the color of emission can also be adjusted by altering the excitation wavelength for a very phosphor, MIP: Eu0.01Tb0.05. As an interesting discovery, the plot of integrated dominant emission intensities of Eu and Tb in phosphor MIP: Eu0.01Tb0.05 versus excitation wavelength exhibits analogical profile with the excitation spectra of Eu3+/Tb3+ single-doped MIP phosphor. Moreover, the representative phosphor MIP: Eu0.01Tb0.05 shows favorable thermal stability. Present work indicates that Mg3In4P6O24 is a promising host material for the fabrication of new phosphors.

The phase relationship of Ti-Hf-Mn system was studied by diffusion triple and equilibrated alloy methods. The isothermal sections at 1373, 1273 and 1173 K for this system were constructed by means of electron probe microanalysis (EPMA) and X-ray diffraction (XRD) for the first time. No ternary phase was found in the system at all these temperatures. Six, seven and seven three-phase equilibria regions have been determined at 1373, 1273 and 1174 K, respectively. In this ternary system, the intermetallic compounds TiMn2, HfMn2 and HfMn exhibit wide solid solution range at those three temperatures. In particular, the solution range of Ti in HfMn phase decreases with the increase of temperature, from 30.5 at% at 1173 K to 26.5 at% at 1373 K. Based on all available experimental data, the Ti-Hf-Mn system was evaluated using the CALPHAD method. The calculation results are in excellent agreement with the experimental data.

The local symmetry of a Eu

Al1−xZnxN polycrystalline powders were synthesized by a modified solid state reaction method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectra, photoluminescence (PL), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID, MPMS-7) magnetometer. The characterized results showed that Zn atoms were doped into the AlN lattice. The obtained Al1−xZnxN showed high crystalline quality. A broad blue band centered at about 450 nm was observed in Zn-doped AlN. Room temperature ferromagnetism was also observed in the doped samples. The substitution of 3-d transition metal of Al in AlN provides a new opportunity to design optical and magnetic materials with good performance.

A series of undoped, Dy3+ and Tm3+ singly-doped, co-doped MgNb2O6 phosphors were prepared by solid-state reaction. Powder X-ray diffraction (XRD), photoluminescence excitation (PLE) and emission (PL) spectrum under UV and VUV excitation, decay lifetimes and CIE chromaticity coordinate were employed to explore the luminescence properties of synthesized phosphors. MgNb2O6 host exhibits a broad emission band from about 350 to 650 nm centered around 451 nm under the UV excitation of 275 nm originating from the NbO6 octahedral groups. Its photoluminescence presents the temperature quenching behavior under VUV excitation. The yellow phosphor MgNb2O6:Dy3+ and blue phosphor MgNb2O6:Tm3+ show the dominant emission peak at 583 nm (4F9/2-6H13/2) upon 275 nm excitation and at 484 nm (1G4-3H6) upon 274 nm, respectively. The Dy3+ and Tm3+ co-doped MgNb2O6 phosphors exhibit tunable colors varying from yellow to warm-white with the emission peak at 583 nm (4F9/2-6H13/2) as concentration of Tm3+ increased. With the increasing concentration of dopant ions, the value of average decay times (t) of characteristic emission of activators monotonously decreases. The stability of representative MNO:0.045Dy3+, 0.02Tm3+ phosphor was investigated base on measurement of temperature-dependent emission spectra. Considering the easy synthesis and special luminescence properties of MgNb2O6-based phosphors, it is extraordinarily meaningful to study for luminescent materials as a fundamental research.

Phase equilibria in Zr-Ni-Pt ternary system have been experimentally determined through diffusion triple and alloy sampling approaches. Based on the results of Electron Probe Microanalysis (EPMA) and x-ray diffraction (XRD), isothermal sections of this system were constructed at 1073 and 1173 K. A new ternary phase denoted as Zr4(Pt,Ni)3 was detected with composition ranging from 2.5 to 29.7 at.% Ni and 40.7 to 12.7 at.% Pt at 1073 K while 2.2 to 25.1 at.% Ni and 40.9 to 17.5 at.% Pt at 1173 K, respectively. Three continuous solutions are formed between binary compounds ZrNi and ZrPt, Zr7Ni10 and Zr7Pt10, ZrNi3 and ZrPt3, and large ternary solubility of Ni in ZrPt4, and of Pt in Zr2Ni and ZrNi5, were observed.

Phase relations of the Ti-Ni-Sn ternary system were investigated via alloy sampling assisted with X-ray diffractometry (XRD) and electron probe micro-analysis (EPMA). A new binary phase with composition of TiSn4 (molar fraction, %) was detected at 508 K. In addition, a supplementary phase (Ti1–x–yNixSny)Ni3 (τ, AuCu3-type) was observed at 873 and 973 K. According to the characterised microscopic structure in various annealed alloys, four ternary phases were detected in Ti-Ni-Sn ternary system: TiNiSn, TiNi2Sn, Ti2Ni2Sn and (Ti1–x–yNixSny)Ni3. Additionally, isothermal sections of Ti-Ni-Sn ternary system at 508, 873 and 973 K were constructed. By comparing three isothermal sections, a peri-eutectic reaction, L+TiNi2Sn→Ni3Sn4+TiNiSn, was deduced, which occurs at a temperature between 873 and 973 K. Furthermore, the solubility of Sn in TiNi and Ni in Ti5Sn3 was detected.

Phase equilibria in the Ti–Zr–Ge ternary system at 1073 and 1173 K were investigated experimentally using equilibrated alloys with electron probe microanalysis and x-ray diffraction analysis. No ternary compounds were detected. Eleven and nine three-phase regions were determined in the Ti–Zr–Ge isothermal section at 1073 and 1173 K, respectively. Intermediate compounds ZrGe2, Zr5Ge4, Zr5Ge3, Ti5Ge4, and Ti5Ge3, possessing large solubility, extended along the Ge isoconcentration line, indicating remarkable substitution of Ti for Zr in the Zr–Ge compounds or of Zr for Ti in the Ti–Ge compounds. The solubility of Ti in ZrGe2 increased from 16.0 at.% at 1073 K to 19.3 at.% at 1173 K, while that of Zr in Ti5Ge3 remained nearly 41.0 at.% at both 1073 and 1173 K.

Phase equilibria in Ti–Ni–Pt ternary system have been experimentally determined through diffusion triple technique combined with alloy samples approach. Assisted with electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques, isothermal sections at 1073 and 1173 K of this system were constructed and existence of ternary phase Ti2(Ni,Pt)3 was confirmed. In addition, binary compounds Ti3Pt5 and TiPt3– were found to be stable at 1073 and 1173 K, and remarkable ternary solubility in some binary compounds was detected, e.g., solubility of Pt in TiNi can be up to about 36% (molar fraction) at 1073 K and 40% (molar fraction) at 1173 K. Furthermore, a ternary invariant transition reaction TiNi3+Ti3Pt5→Ti2(Ni,Pt)3+TiPt3+ at a temperature between 1073 and 1173 K was deduced.

Phase equilibria in the Ti-Co-Pt ternary system were measured through diffusion triple and alloy sampling. Based on the results from Electron Probe Microanalysis (EPMA) and X-ray diffraction (XRD) techniques, the isothermal sections of the Ti-Co-Pt system were constructed, which consist of 16 and 13 three-phased regions at 973 and 1173 K, respectively. A new ternary phase τ was detected, which contains 23.6–29.9 at% Pt at 973 K and 27.4–40.1 at% Pt at 1173 K. Furthermore, an invariant reaction between 973 and 1173 K was deduced, i.e. τ + Ti4Pt3 ↔ Ti3Pt + TiPt. By the way, the solubilities of Pt mainly substituting for Co in TiCo and TiCo3 respectively increase from 22.4 at% and 26.1 at% at 973 K to 23.8 at% and 33.1 at% at 1173 K.

Scintillating materials, as a class of luminescent materials, are highly demanded for practical use in the high-energy detection. However, the applications are often hampered by their low light yield (LY) or long decay time for many traditional scintillators. In this work, upon nitrogen anion doping, scintillation performance in layered borate Ba 3 In(B 3 O 6 ) 3 (BIB) has been excellently enhanced with high XEL intensity of ～3 times as large as that of commercial Bi 4 Ge 3 O 12 (BGO) and ultra-fast fluorescent decay time of ～1.25 ns. To shed light on origins of the intrinsic violet-blue emission, we measured the in-situ vacuum ultraviolet excited (VUV) emission spectra of N-BIB ceramic. Combined with experiments and first principles calculations, the band-gap reduction and donor-acceptor density increasing by nitrogen (N) doping is responsible for the enhancement of scintillation performance for N-doped Ba 3 In(B 3 O 6 ) 3 . Moreover, nitrogen anion doping rather than conventional cation doping is found to be also applicable to other intrinsic luminescent materials for enhancing performance.

Phase relations in Cu–Ti–Hf ternary system have been studied by diffusion triple technique supplemented with typical alloy sampling method. Based on results from electron-probe microscopy analysis and X-ray diffraction, isothermal sections of the Cu–Ti–Hf system at 800 and 700 °C were established, which consist of ten and nine three-phase regions, respectively. It is observed that Ti can completely substitute Hf in the CuHf2 phase, indicating formation of a continuous solid solution Cu(Ti,Hf)2. Hf can substitute about 20% Ti in the phase CuTi, while solubility of Ti in Cu10Hf7 and Cu51Hf14 phases reaches to 14 and 11 at.% at 800 °C, respectively. The Cu8Hf3 phase in existence at 800 °C was proved to be unstable at 700 °C. In addition, the elastic modulus and hardness of solid solution Cu(Ti,Hf)2 were determined by using nano-indentation techniques.

Although the ternary chalcopyrite compound Cu2Ga4Te7 has relatively high thermal conductivity and electrical resistivity, it has a high carrier concentration, thus making it a good thermoelectric candidate. In this work we substitute Sb for Cu in this compound, aiming at engineering both the electrical and thermal properties. Rietveld refinement revealed that the nominal compounds Cu2−xSbxGa4Te7 (x = 0–0.1) crystallize with the crystal structure of CuGaTe2 with the real compositions deviating from those of their nominal ones. Besides, Sb resides in Cu sites, which increases both the effective mass and the Hall carrier concentration. Therefore, the Seebeck coefficient increases at high temperatures, and the lattice thermal conductivity reduces due to increased phonon scattering from point defects and electron–phonon interactions. As a consequence, the thermoelectric (TE) performance improves with the highest TE figure of merit (ZT) of 0.58 at 803 K. This value is about 0.21 higher than that of the pristine Cu2Ga4Te7.

Single-component white phosphors stand a good chance to serve in the next-generation high-power white light-emitting diodes. Because of low thermal stability and containing lanthanide ions with reduced valence state, most of reported phosphors usually suffer unstable color of lighting for practical packaging and comparably complex synthetic processes. In this work, we present a type of novel color-tunable blue–white–yellow-emitting MgIn2P4O14:Tm3+/Dy3+ phosphor with high thermal stability, which can be easily fabricated in air. Under UV excitation, the MgIn2P4O14:Tm0.02Dy0.03 white phosphor exhibits negligible thermal-quenching behavior, with a 99.5% intensity retention at 150 °C, relative to its initial value at room temperature. The phosphor host MgIn2P4O14 was synthesized and reported for the first time. MgIn2P4O14 crystallizes in the space group of C2/c (No. 15) with a novel layered structure built of alternate anionic and cationic layers. Its disordering structure, with Mg and In atoms co-occupying t...

In present work, the phase equilibrium relations in the Ti-Ni-Hf ternary system, which are of great importance for the design of Ti-Ni based high temperature shape memory alloys, were investigated using diffusion triples and sixteen key equilibrated alloys. Based on the experimental results from electron-probe microscopy analysis (EPMA) and X-ray diffraction (XRD) techniques, two isothermal sections were constructed, which consist of 13 and 12 three-phase regions at 900 °C and 800 °C, respectively. Hf can substitute for Ti in TiNi and Ti 2 Ni phases increasing from 30, 62 at% at 800 °C to 36, 64 at% at 900 °C, respectively. The Hf 7 Ni 10 and Hf 9 Ni 11 phases show wide ternary composition ranges, while the solubility of Ti in HfNi 5 , Hf 2 Ni 7 , and HfNi phases are relatively limited. A new ternary phase of τ was detected for the first time, and the stoichiometry of τ phase is close to Ni:(Hf,Ti) = 11:14, with Ti substituting for Hf from ～5 at% to ～22 at%. The single-phase region of the τ phase became narrow as the decreasing of annealing temperature. Based on comparison of phase relations at 900 °C and 800 °C, it is speculated there is an invariant reaction TiNi + τ → HfNi + Ti 2 Ni at between 900 °C and 800 °C.

Phase relations in Ti-Cu-Pt ternary system have been studied through diffusion- triple technique combined with alloy sampling. Assisted with Electron Probe Microanalysis (EPMA) and x-ray diffraction (XRD) techniques, isothermal sections at 1073 and 973 K of this ternary system were constructed, which consist of 16 three-phased regions at 1073 and 973 K, where two ternary phases, respectively formulated as Ti(Cu,Pt)2 and Ti(Cu,Pt)3, were detected to exist stably at 1073 and 973 K. By the way, the 2 binary compounds, Ti3Pt5 and TiPt3− were found to be stable at 1073 and 973 K.

Novel single-phased white-light-emitting and color tunable LiSrBO 3 :Dy 3+ , Tm 3+ , Eu 3+ phosphors were synthesized by solid-state reaction method. Their crystal structures were refined by the Rietveld method using Fullprof_suite program on the basis of powder diffraction data. And their luminescent properties were characterized mainly by ultraviolet (UV) visible photoluminescence excitation (PLE), photoluminescence (PL), and Decay lifetime. The energy transfer among activators in the LiSrBO 3 host has been investigated. The chromaticity diagram shows that the Dy 3+ , Tm 3+ co-doped LiSrBO 3 phosphors could emit white light and the color was tunable from cold white to warm white by Eu 3+ co-activated. The excitation spectra indicate that these phosphors can be effectively excited by ultraviolet 350–400 nm, matching well with the dominant emission band of a light-emitting-diode (LED) chip. Rare-earth activators were determined to be completely dissolved into the host lattice and occupied the 4 e sites deviated from an inversion center by virtue of XRD, structure refinement and photoluminescence features. Concentration quenching of phosphors LSBO: Na + , Tm 3+ occurs at the doping concentration x=0.03. According to their decay curves, the calculated lifetime of LSBO:0.005Dy 3+ , 0.005Tm 3+ , LSBO:0.01Dy 3+ , 0.005Tm 3+ , and LSBO:0.015Dy 3+ , 0.005Tm 3+ phosphors are 0.99 ms, 0.986 ms, and 0.96 ms, respectively. The present work suggests that these novel phosphors may have potential applications for white LEDs.

Isothermal sections of Cr-Ge-Ti ternary system at 1073 K and 1273 K have been studied through alloy sampling. Results of electron probe microanalysis (EPMA) and X-ray diffraction (XRD) show that there is no ternary compound at these temperatures, and intermetallics Cr 3 Ge, Cr 11 Ge 8 , Ge 3 Ti 5 and Ge 5 Ti 6 possess huge solubility extending along the isoconcentration of Ge, indicating substitution of Ti for Cr in Cr-Ge compounds or of Cr for Ti in Ge-Ti compounds. And the maximum solubility of Cr in Ge 5 Ti 6 at 1073 K is found to be 39.5 at.%. Finally, substitution of Ti by Cr in Ge 5 Ti 6 is confirmed by Rietveld refinement.

In the investigation of MgO–Y2O3–B2O3 system, six three-phase regions, five binary compounds, and one ternary compound MgYB5O10 were confirmed in the subsolidus phase relations. Single-phase powder sample of MgYB5O10 was successfully prepared through solution synthesis method. By using the Rietveld method from the step-scanning X-ray powder diffraction data, the crystal structure of MgYB5O10 was determined. It crystallizes in the monoclinic system with the space group P121/c1 and lattice parameters a = 8.5113(2) Å, b = 7.5892(2) Å, c = 12.2460(3) Å, β = 130.200(1)°, and Z = 4. The infrared spectrum of MgYB5O10 at room temperature demonstrates the existence of BO3 and BO4 groups. The UV–visible spectrum shows a wide absorption band within the range of 190–400 nm, while the absorption in the visible region is negligible. According to the electronic structure derived by first-principles calculations, MgYB5O10 is an insulator with a wide indirect energy band gap of about 5.95 eV. Layered structural characteristics, existence of one-dimensional YnO8n+2 chains, and the large band gap should be the immanent reason why MgYB5O10-based materials have exhibited outstanding performances in the luminescence field.