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Double perovskite La2-xCaxCoMnO6 (x=0, 0.1, 0.2, 0.5) ceramics samples were synthesized by the standard solid-state reaction method. The crystal structures have been confirmed to be monoclinic perovskite structure with space group of P21/n at room temperature by the powder x-ray diffraction (Cu-Ka). The grains of the samples are relatively dense and distribute in random directions from the scanning electron microscope patterns. Holes are doped into La2CoMnO6 with the substitution of the Ca2+ ions in La-site, and further lead to the valences of Mn ions and Co ions transforming from Mn4+ and Co2+ to Mn3+ and Co3+, respectively. Ferromagnetic coupling of Mn4+-O2--Co2+ and antiferromagnetic coupling of Mn3+-O2--Co3+ are coexistent in La2-xCaxCoMnO6 system, which correspond to two transitions existed in field-cooling magnetization versus temperature curves. Curie temperature of La2-xCaxCoMnO6 system decreases with the increasing of Ca-substitution amount. The coexistence of different magnetic phases leads to the exchange bias effect. [ABSTRACT FROM AUTHOR]

Double perovskite La2-xCaxCoMnO6 (x=0, 0.1, 0.2, 0.5) ceramics samples were synthesized by the standard solid-state reaction method. The crystal structures have been confirmed to be monoclinic perovskite structure with space group of P21/n at room temperature by the powder x-ray diffraction (Cu-Ka). The grains of the samples are relatively dense and distribute in random directions from the scanning electron microscope patterns. Holes are doped into La2CoMnO6 with the substitution of the Ca2+ ions in La-site, and further lead to the valences of Mn ions and Co ions transforming from Mn4+ and Co2+ to Mn3+ and Co3+, respectively. Ferromagnetic coupling of Mn4+-O2--Co2+ and antiferromagnetic coupling of Mn3+-O2--Co3+ are coexistent in La2-xCaxCoMnO6 system, which correspond to two transitions existed in field-cooling magnetization versus temperature curves. Curie temperature of La2-xCaxCoMnO6 system decreases with the increasing of Ca-substitution amount. The coexistence of different magnetic phases leads to the exchange bias effect. [ABSTRACT FROM AUTHOR]

Polycrystalline La0.9Sr0.1Cr1−xCoxO3 (0.0 ≤ x ≤ 0.4) solid solutions were synthesized by a sol-gel method using citric acid as chelating agent. Thermogravimetric and differential thermal analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction (XRD) techniques are used to explore precursor decomposition and to establish adequate calcination temperature for the preparation of the polycrystalline. The samples obtained after calcination at 750 °C were characterized by several techniques. X-ray diffraction analyses reveal that that B-site doping of Co may lead to the transformation of its crystal structure from an orthorhombic to a rhombohedral phase, when Co content x ≥ 0.2. Scanning electron microscopy (SEM) shows that all samples have almost spherical nanoparticles with high crystallization. The increase in the fraction of the doped-Co leads to high agglomeration of particles while the porosity increases. Electrochemical measurements indicate that the catalytic activity toward methanol oxidation in alkaline solution is strongly influenced by cobalt doping. La0.9Sr0.1Cr0.6Co0.4O3-modified electrodes responded extremely well to methanol by giving high anodic current for methanol oxidation (over 46 mA cm−2 at 0.650 V vs Hg/HgO). [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Solid-state perovskite nanocrystals are promising coherent light sources, as there is optical feedback within the crystal structure. In order to utilize the high performance of perovskites for on-chip applications, or observe new physical phenomena, these crystals must be integrated with pre-fabricated electronic or photonic structures. However, the material's fragility has made the deterministic transfer a great challenge thus far. Here, we report the first deterministic transfer of perovskite nanocrystals with sub-micron accuracy. Cesium lead halide (CsPbI 3) nanocrystals were directly synthesized on flexible polydimethylsiloxane (PDMS) stamps via chemical vapor deposition (CVD) and subsequently transferred onto arbitrary substrates/structures. We demonstrated the transfer of a CsPbI 3 crystalline nanoplate (NP) onto an 8 µm fiber core and achieved single-mode whispering gallery mode lasing. Our method can be extended to a variety of other arbitrary substrates (e.g., electrodes, photonic structures, micromechanical systems), laying the foundations for previously unattainable opportunities in perovskites-based devices. [ABSTRACT FROM AUTHOR]

A systematic investigation on the structure, magnetism, magnetocaloric effect, and critical behaviors of multiferroic Lu 2 NiMnO 6 synthesized by sol-gel method are reported. This compound crystallizes in a monoclinic structure with the space group P2 1 /n. Upon decreasing temperature, a single magnetic transition from paramagnetic to ferromagnetic phase has been observed, around which considerable magnetic entropy changes can be obtained. Besides, evaluation of the critical exponents are performed using various techniques, like the modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis based on the magnetic data around magnetic transition temperature. The obtained critical exponent values are found to be coincided and comparable with those predicted by the mean-field model, which are also confirmed by the single scaling equation: m  =  f ± (h), where m and h are the renormalized magnetization and field, respectively by observation of isotherm M (H) curves below and above the critical temperatures collapsing into two independent universal branches. The exponents determined in this study are in good agreement with those calculated from the renormalization group approach for a three-dimensional system coupled with the attractive long-range interactions between spins that decay as J ( r ) ∼ r − ( 3 + σ ) with σ = 1.325. [ABSTRACT FROM AUTHOR]

Double perovskite Sr 2 Ni 0.75 Mg 0.25 MoO 6-δ powders were synthesized by the combustion method using systems containing nitrates and varying amounts of the following organic components: glycine, glycerol, and polyvinyl alcohol. The characteristics (temperature, gas composition, etc.) of the synthesis process were studied and the optimal conditions for obtaining single-phase samples were determined. It was established that the usage of one-and-a-half excess of glycerol as organic component provides the formation single-phase complex oxide. The crystal structure of the obtained complex oxide, which is of interest as an anode material for solid oxide fuel cells, was refined and its physico-chemical properties (specific surface area, particle size, electrical conductivity, and catalytic activity in the reaction of methane oxidation) were investigated. [ABSTRACT FROM AUTHOR]

Incorporation of dopant amounts of the divalent transition metal cation Mn 2+ into the oxyfluoride material Sr 3- x Mn x M O 4 F ( M  = Al, Ga; 0 ≤  x  ≤ 0.1) yields green powders which vary in hue depending on the identity of M . Treatment of these phases with post-synthesis annealing under reducing conditions produces anion deficient phases according to Sr 3- x Mn x M O 4-α F 1-δ displaying vivid purple coloration. Intense colors are likely due to small amounts of Mn 3+ on the tetrahedral M site. Full structural characterization based upon powder X-ray diffraction (PXRD), neutron powder diffraction (NPD), and thermogravimetric analysis (TGA) data are presented herein, demonstrating that the Sr 3 -x A x M O 4 F ( A  = Ca, Sr, Ba; M  = Al, Ga) anti-perovskite structure can readily accommodate first row transition metals. [ABSTRACT FROM AUTHOR]

Layered oxides, A 2 B'B″O 6 , with small ions at A-site mostly occupied by unusual-metals like transitional metals are of great importance due to their strong and unusual magnetic interactions and technical applications. Due to small tolerance factors it is very difficult to synthesize such materials in ambient pressure and temperature. Depending upon the variation in temperature and pressure, same composition of the above mentioned materials can be crystallized with different structural arrangements. The effect of pressure and synthetic condition of different materials has been described in this review. The literature data on the effects of the A-site occupation by small ions on the structure and properties are summarized. Finally structural changes and dissimilar properties of high temperature and pressure synthesized recent developed materials are compared with the materials with usual B-site ordered double perovskite. [ABSTRACT FROM AUTHOR]

A series of double perovskite Gd2(1−x)MgTiO6:xEu3+ (x = 0.01, 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5) phosphors were successfully synthesized. Two rare earth ions occupy the A-site in this host, which benefits the doping of Eu3+ ions. The crystal structure, microstructure were examined by X-ray diffraction and scanning electron microscopy. Luminescence properties, such as excitation and emission spectra, CIE coordinates and concentration quenching were systematically investigated. A weak magnetic dipole transition (5D0–7F1, 590 nm) and a strong electric dipole transition (5D0–7F2, 616 nm) existed in the emission spectra. The quenching concentration for hypersensitive electric dipole transition of Eu3+ reached up to 15.0 mol%. The delayed concentration quenching was observed in Gd2MgTiO6:Eu3+ phosphors. The theoretical quenching concentration was obtained based on Ozawa’s theory, and the quenching mechanism on Dexter’s theory. All the results indicate that Gd2MgTiO6:Eu3+ has great potential in solid state lighting. [ABSTRACT FROM AUTHOR]

A series of chromite perovskites with the general formula Ln 1−x M x Cr 0.9 Ni 0.1 O 3 (Ln = La and/or Nd; M = Sr and/or Ca; x ≤ 0.25) has been prepared by three combustion synthesis routes using a different combustible substance each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, < r A > ≈ 1.22 Å, and cation size disorder, σ 2 (r A ) ≈ 0.0001 Å 2 , but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Cell parameters, grain sizes, expansion coefficients and conductivities all are found to be dependent on x and the combustible substance used. The most interesting relationship is the negative dependence of the conductivity with x under H 2 atmosphere: conductivity decreases with doping which is the opposite to the expected behavior for a p-type doped perovskites and has not been reported before. [ABSTRACT FROM AUTHOR]

A series of Eu 3+ ions activated double perovskite CaLaMgSbO 6 phosphors were successfully synthesized. Crystal structure was investigated by XRD and the results showed that this double perovskite exhibited rock-salt ordering of B-site ions. High-resolution transmission electron microscopy was used to prove the existence of B-site ordering. Thereafter, luminescence properties of the as-prepared powders were discussed in detail. The phosphors could be well excited by ultraviolet, near ultraviolet, and blue light. The quenching concentration for the transition of 5 D 0 - 7 F 2 reached up to 50.0 mol%. The theoretical quenching concentration and quenching mechanism were discussed in detail. Excellent thermal stability of this double perovskite phosphor was obtained and the quenching mechanism was investigated based on the configurational coordinate diagram. The CIE coordinates showed that this double perovskite phosphor had great potential in solid state lighting. [ABSTRACT FROM AUTHOR]

Although all-inorganic perovskite CsPbBr 3 perovskites quantum dots (QDs) have garnered enormous interest in light emitting diodes, nonetheless limited attention has been paid to the perovskite-related CsPb 2 Br 5 nanoplatelets . Herein, we prepared perovskite-related CsPb 2 Br 5 nanoplatelets (NPLs) by a facile injection method. The synthesised CsPb 2 Br 5 NPLs showed single tetragonal crystalline phase with a uniform square shape and a high photoluminescence (PL) emission around 520 nm (PL quantum yield (QY) > 85%). In addition, we have demonstrated the fabrication of highly efficient CsPb 2 Br 5 NPLs-based green light emitting diodes with the highest luminance of 800 cd/m 2 and a relative low turn-on voltage of 3.0 V. [ABSTRACT FROM AUTHOR]

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This work investigates the partial substitution of Zn in the B-site of perovskite as Ba 0.5 Sr 0.5 (Co 0.8 Fe 0.2 ) 1− x Zn x O 3− δ . The membranes were tested for oxygen separation from air and Zn incorporation into the BSCFZ cubic crystal structure proved to be effective as oxygen fluxes increased as compared with a pure BSCF (x = 0, no Zn). This was attribute to the increase in oxygen vacancy concentration as a function of Zn concentration. As a result, oxygen fluxes for the BSCFZ membranes were 200% (700 °C) and 32% (900 °C) higher than the BSCF analogue membrane. However, the correlation between oxygen vacancy concentration and oxygen flux diverged for Zn concentrations x ≥ 0.08, which was associated with the shift and broadening of the main XRD peak 2θ = 31.81° of the BSCFZ cubic structure caused by an additional oxide phase (ZnO). Zn doping also affected the microstructure of the sintered BSCFZ membranes. Grain boundary dimensions reduced as Zn substitution in the B-site increased to x = 0.06 up to 800 °C, resulting in improved oxygen fluxes. Contrary to this, high Zn concentration x ≥ 0.08 increased grain boundary and reduced oxygen fluxes. Therefore, the Zn solubility into BSCF impact upon the oxygen vacancy and microstructural formation, which in turn affected the transport of oxygen ions through the membrane. [ABSTRACT FROM AUTHOR]

Oxynitride type complex perovskites AM 0.2 Nb 0.8 O 3− x N x (A = Sr, Ba; M = Li, Na, Mg) were newly synthesized by the solid state diffusion of Li + , Na + , or Mg 2+ into the layered oxide, A 5 Nb 4 O 15 , with concurrent O/N substitution. Neutron and synchrotron X-ray Rietveld refinement showed that SrLi 0.2 Nb 0.8 O 2.8 N 0.2 , SrNa 0.2 Nb 0.8 O 2.8 N 0.2 , and SrMg 0.2 Nb 0.8 O 2.6 N 0.4 had body-centered tetragonal symmetry ( I 4/ mcm ), while those with A = Ba had simple cubic symmetry ( Pm 3 ̅ m ). In the tetragonal Sr-compounds, the nitrogen atoms were localized on the c -axial 4 a site. However, the octahedral cations, M/Nb (M = Li, Na, Mg) were distributed randomly in all six compounds. The lattice volume of AM 0.2 Nb 0.8 O 3− x N x was dependent on various factors including the type of A and the electronegativity of M. Compared to the simple perovskites, ANbO 2 N (A = Sr, Ba), AM 0.2 Nb 0.8 O 3− x N x had wider band gaps (1.76–2.15 eV for A = Sr and 1.65–2.10 eV for A = Ba), but significantly lower sub-gap absorption. [ABSTRACT FROM AUTHOR]

Defect perovskites (He2-x□x)(CaZr)F6 can be prepared by inserting helium into CaZrF6 at high pressure. They can be recovered to ambient pressure at low temperature. There are no prior examples of perovskites with noble gases on the A-sites. The insertion of helium gas into CaZrF6 both elastically stiffens the material and reduces the magnitude of its negative thermal expansion. It also suppresses the onset of structural disorder, which is seen on compression in other media. Measurements of the gas released on warming to room temperature and Rietveld analyses of neutron diffraction data at low temperature indicate that exposure to helium gas at 500 MPa leads to a stoichiometry close to (He1□1)(CaZr)F6. Helium has a much higher solubility in CaZrF6 than silica glass or crystobalite. An analogue with composition (H2)2(CaZr)F6 would have a volumetric hydrogen storage capacity greater than current US DOE targets. We anticipate that other hybrid perovskites with small neutral molecules on the A-site can also be prepared and that they will display a rich structural chemistry. [ABSTRACT FROM AUTHOR]

The influence of BiFeO3on phase formation, crystal structure, and dielectric properties of solid solutions close to the Morphotropic Phase Boundary in the (Na0.5Bi0.5)TiO3- (K0.5Bi0.5)TiO3system was studied. The formation of samples with pure perovskite structure was proved, increase in the unit cell parameters and in theTmvalue while decrease in elelctroconductivity and dielectric loss stimulated by the BiFeO3addition were revealed. [ABSTRACT FROM PUBLISHER]

In this work we report the synthesis and structural, electronic and magnetic properties of La1.5Ca0.5CoMnO6 double-perovskite. This is a re-entrant spin cluster material which exhibits a non-negligible negative exchange bias effect when it is cooled in zero magnetic field from an unmagnetized state down to low temperature. X-ray powder diffraction, X-ray photoelectron spectroscopy and magnetometry results indicate mixed valence state at Co site, leading to competing magnetic phases and uncompensated spins at the magnetic interfaces. We compare the results for this Ca-doped material with those reported for the resemblant compound La1.5Sr0.5CoMnO6, and discuss the much smaller spontaneous exchange bias effect observed for the former in terms of its structural and magnetic particularities. For La1.5Ca0.5CoMnO6, when successive magnetization loops are carried, the spontaneous exchange bias field inverts its sign from negative to positive from the first to the second measurement. We discuss this behavior based on the disorder at the magnetic interfaces, related to the presence of a glassy phase. This compound also exhibits a large conventional exchange bias, for which there is no sign inversion of the exchange bias field for consecutive cycles. [ABSTRACT FROM AUTHOR]

We investigated the formation of single-crystal CH 3 NH 3 PbCl 3 and CH 3 NH 3 PbI 3 perovskites by cast-capping method. This very simple but high efficiency technique based on modified solution process was successful to grow large-domain single crystals up to a millimeter size. Their X-ray diffraction patterns revealed that both crystals grew in the cubic form. The (100) planes of both crystals grew predominantly in contact with the substrate surface. The present technique helps further studies as an alternative method to fabricate high performance functional devices. [ABSTRACT FROM AUTHOR]

The structural details of the ordered hexagonal oxyfluoride Na 2 CaVO 4 F prepared by solid-state synthesis using stoichiometric amounts of V 2 O 5 , CaCO 3 , Na 2 CO 3 and NaF were characterized using high-resolution neutron powder diffraction. The structural changes between 25 °C and 750 °C revealed that the two structural subunits in this material behave different when heated: there is an expansion of the face-shared FNa 4 Ca 2 octahedra while the VO 4 tetrahedra due to increased thermal disorder reveal marginal bond contractions. Bond valences and the global instability index point to significant structural disorder at 750 °C. [ABSTRACT FROM AUTHOR]

Double perovskites Ba 1+x La 1−x MnSbO 6 were synthesized by traditional ceramic methods in air as polycrystalline powders. The 0.1 ≤ x ≤ 0.2 compounds belong to the I 2/m monoclinic space group, while the perovskites with x ≥ 0.3 belong to the I 4/m tetragonal space group. The effective presence of mixtures of Mn 2+ /Mn 3+ has been well established by X-ray Emission Spectroscopy. Ba 1+x La 1−x MnSbO 6 (0.1 ≤ x ≤ 0.5) oxides display signs of superparamagnetism in the 40–160 K range, which arises from 3D-nanoclusters formed in regions which are rich in Mn 2+/3+ –O–Mn 2+/3+ superexchange paths originated by the antisite disorder. The analysis of the M vs H hysteresis loops shows that, as x increases, the number of 3D-nanoclusters rises and the number of magnetic ions in the 3D-nanoclusters decreases. The small 3D-nanoclusters cannot sustain magnetic order inside them and this is the reason for the absence of superparamagnetism for x = 0.6 and 0.7. The analysis of the M vs H curves also shows the presence of a weak ferromagnetism which is generated by the canting of the spins in the antiferromagnetic matrix. Neutron Powder Diffraction data reveals that there is long range antiferromagnetic ordering below ≈20 K. [ABSTRACT FROM AUTHOR]

A novel phosphor, Sr 2 LaNbO 6 :Mn 4+ , is synthesized by conventional solid-state reaction. The phosphor can be excited at 300–500 nm and emit a deep-red light. An emission band peak of 694 nm is observed from the spin-forbidden transition 2 E → 4 A 2 of Mn 4+ ions. Energy transfer between the Mn 4+ –Mn 4+ pairs decreases fluorescence decay time from 0.815 ms to 0.512 ms. The resistance of luminescence against thermal impact is also investigated by emission spectroscopy at heating temperatures from 300 K to 500 K. The calculated activation energy Δ E (∼0.345 eV) demonstrate good thermal stability of the phosphors. All these results indicate that the phosphor can be applied in white-light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of perovskite BaTb1-xBixO3 (0.0≤ x≤0.25) solid solutions were synthesized by a typical solid-state method. Their structures were analyzed by a combination of X-ray diffraction, neutron diffraction, and selected-area electron diffraction. All of the materials crystalize in the P1 space group [a = 6.0582(1) Å, b = 6.0473(1) Å, c = 6.0693(1) Å, α = 60.00(1)°, β = 59.84(1)°, γ = 60.06(1)° for x = 0.0 at room temperature]. Magnetic measurements revealed that the magnetic-ordering temperature decreases with increasing Bi content in BaTb1-xBixO3; therefore, the presence of Bi decreases the magnetic interactions of Tb. Furthermore, the magnetic structure for BaTb1-xBixO3 has been fully described in space group P1. [ABSTRACT FROM AUTHOR]

A series of perovskite BaTb1-xBixO3 (0.0≤ x≤0.25) solid solutions were synthesized by a typical solid-state method. Their structures were analyzed by a combination of X-ray diffraction, neutron diffraction, and selected-area electron diffraction. All of the materials crystalize in the P1 space group [a = 6.0582(1) Å, b = 6.0473(1) Å, c = 6.0693(1) Å, α = 60.00(1)°, β = 59.84(1)°, γ = 60.06(1)° for x = 0.0 at room temperature]. Magnetic measurements revealed that the magnetic-ordering temperature decreases with increasing Bi content in BaTb1-xBixO3; therefore, the presence of Bi decreases the magnetic interactions of Tb. Furthermore, the magnetic structure for BaTb1-xBixO3 has been fully described in space group P1. [ABSTRACT FROM AUTHOR]

Double perovskite related oxides A 2 ZnTiO 6 (A = Pr, Gd) have been successfully synthesized by solid state reaction and investigated as photocatalysts for the first time. The two layered titanates mainly demonstrate absorbances under UV irradiation, except for several sharp absorption bands above 400 nm for Pr 2 ZnTiO 6 . Therefore, a series of photocatalysts by doping A 2 ZnTiO 6 (A = Pr, Gd) with Cr have been developed in the hope to improve their absorption in the visible light region. The successful incorporation of Cr was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, UV–vis DRS and PL. The characterization results suggested that Cr was present mainly in the form of Cr3+, with only a small amount of Cr6+ species. It served as an efficient dopant for the extension of visible light absorbance and improved photocatalytic activities under solar light irradiation. For both Pr 2 ZnTiO 6 and Gd 2 ZnTiO 6 , the valence band (VB) was composed of hybridized states of the Zn 3d, O 2p and the conduction band (CB) has major contribution from Zn 4s, Ti 3d orbitals. For Cr doped samples, the newly formed spin-polarized valence band in the middle of the band gap that primarily arises from Cr 3d orbitals was responsible for the improved optical and photocatalytic properties. [ABSTRACT FROM AUTHOR]

A new organic–inorganic 2D hybrid perovskite [NH 3 (CH 2 ) 4 NH 3 ]CoCl 4 ,1,4butane diammonium tetra-chlorocobaltate, has been synthesized. Blue prismatic single crystals were grown from ethanolic solution in 1:1 stoichiometric ratio (organic/inorganic) by gradual cooling to room temperature after heating at 70 °C for 1 h. The hybrid crystallizes in a triclinic phase with the centrosymetric space group P 1 ¯ . Its unit cell parameters are a =7.2869 (2) Å, b =8.1506 (2) Å, c =10.4127 (3) Å, α =77.2950 (12)°, β =80.0588 (11)°, γ =82.8373 (12)° and Z =2. The final R factor is 0.064. The structure consists of organic dications [NH 3 (CH 2 ) 4 NH 3 ] 2+ which act as spacer between layers of inorganic dianions [CoCl 4 ] 2 − in which CoII ions are coordinated by four Cl atoms in an isolated tetrahedral structure. The organic and inorganic layers form infinite 2D sheets which are parallel to the ac plane, stacking alternatively along the b -axis, and are connected via N–H…. Cl hydrogen bonds. The lamellar structure of the 1,4 butane diammonium tetrachlorocobaltate hybrid is typically considered as naturally self-assembled multiple quantum wells (MQW). The calculated lattice potential energy U pot (kJ/mol) and lattice enthalpy Δ H L (kJ/mol) are inversely proportional to the molecular volume V m (nm 3 ) of perovskite hybrid of the formula [NH 3 (CH 2 ) n NH 3 ]CoCl 4 , n=3–9. [ABSTRACT FROM AUTHOR]

The synthesis of multicomponent perovskites ( Ln 0.25 Mn 0.75 )(Al 0.25 Ti 0.75 )O 3 ( Ln =La, Pr, Nd, Sm, Gd, Tb, Dy, Y) have been investigated using a high-pressure and high-temperature (6 GPa, 1175 °C) technique. When Ln 3+ is larger La 3+ , Pr 3+ , Nd 3+ , the A-site ordered perovskites, Ln Mn 3 (Al 0.25 Ti 0.75 ) 4 O 12 in Im -3, have been successfully synthesized. The A-site partially disordered one, (Sm 0.80 Mn 0.20 )(Sm 0.07 Mn 0.93 ) 3 (Al 0.25 Ti 0.75 ) 4 O 12 is also obtained. In the case of smaller Gd 3+ , Tb 3+ , Dy 3+ , we have obtained no single phase but two decomposed perovskite phases. When Ln 3+ is much smaller Y 3+ , it is crystallized as an A-site disorder one in Pnma . The Rietveld structural refinements of the A-site ordered and partially disordered perovskites indicate that the tilting of (Al/Ti)O 6 octahedrons for the A-site ions ordering is correlated with the (Al/Ti)–O and Ln –O bond lengths to optimize the coordination of the A - and A′ -sites. The phase stability of the A-site ordered perovskites is discussed from the viewpoint of this correlation. [ABSTRACT FROM AUTHOR]

The bismuth based perovskite with the structure (CH3NH3)3Bi2I9 (MBI) is rapidly emerging as eco-friendly and stable semiconducting material as a substitute for the lead halide perovskites. A relatively higher bandgap of MBI (about 2.1 eV) has been found to be a bottleneck in realizing the high photovoltaic performance similar to that of lead halide based perovskites. We demonstrate the bandgap engineering of novel bismuth based perovskites obtained by in situ sulfur doping of MBI via the thermal decomposition of Bi(xt)3 (xt = ethyl xanthate) precursor. Colors of the obtained films clearly changed from orange to black when annealed from 80 to 120 °C. Formation of sulfur doped MA3Bi2I9 was confirmed by XRD and the presence of sulfur was confirmed through XPS. In this work, obtained sulfur doped bismuth perovskites exhibited a bandgap of 1.45 eV which is even lower than that of most commonly used lead halide perovskites. Hall-Effect measurements showed that the carrier concentration and mobility are much higher as compared to that of undoped MA3Bi2I9. [ABSTRACT FROM AUTHOR]

A series of new uranium-bearing layered perovskites with the Aurivillius-derived structures has been studied by X-ray diffraction and photoelectron spectroscopy. The results of both methods are in very good agreement and confirm the structural motifs suggested for these compounds. A new oxyfluoride Ba 2 F 2 UO 4 has been prepared and characterized. [ABSTRACT FROM AUTHOR]

Novel La 0.5 Bi 0.2 Ba 0.2 Mn 0.1 FeO 3−δ , with a perovskite-like structure, was synthesized by using the citric acid sol-gel route. The powder was precalcined at 400 °C and then separate portions were annealed at temperatures of 500, 600, 700, 800 and 900 °C. Transmission electron microscopy and powder X-ray diffraction analysis of the powders showed that they contain crystalline rhombohedral perovskite-type nanoparticles. The BET specific surface areas ranged between 4.19 and 27.8 m 2 g −1 , decreasing with increasing annealing temperature. Vibrating sample magnetometer analysis of the hysteresis loops showed an increase in coercive field with increasing annealing temperature. Very large coercive fields of about 5.60 kOe were obtained for samples annealed at 900 °C. This could prove useful in making magnetic recording materials. Photoluminescence spectroscopy showed that all the powders were active in the visible region and could be useful for visible light photodegradation of pollutants. The powders were all screened for photocatalytic activity against an organic dye (rhodamine B) in the visible region of the solar spectrum and the photocatalytic activities were good particularly for powders annealed at 900 °C. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of a double perovskite oxide Ba 2 CeSbO 6 (BCSO) synthesized by solid state reaction technique have been investigated. The Rietveld refinement of the X-ray diffraction pattern of BCSO suggests the monoclinic crystal structure at room temperature with P2 1 /n space group. The vibrational properties of BCSO are investigated by the Fourier transform Infrared and Raman spectroscopy. The Raman spectrum confirms the B-site ordering of cations in BCSO. The temperature dependent magnetic susceptibility data in the field cooled mode show the anti-ferromagnetic behaviour of BCSO below 59 K. The core level X-ray photoemission (XPS) spectrum of Ce-3d and Sb-3d states confirms the presence of multiple oxidation states of these cations. The presence of both the Ce 3+ and Ce 4+ ions in BCSO gives the 4f 4−δ intermediate valence state which may reduce the effective magnetic moment with respect to the system having single valence Ce 3+ ion. [ABSTRACT FROM AUTHOR]

In this paper, a new layered hybrid perovskite film ((EDA)(MA) 2 [Pb 3 I 10 ]) was synthesized through one-step method. Ethylenediamine (EDA) cation was introduced into the perovskite lattice to synthesize a layered structure with improved resistance to degradation by humidity. The effects of humidity and time on crystal structure, composition, morphology and absorption spectra of (EDA)(MA) 2 [Pb 3 I 10 ] were analyzed by in situ grazing incidence X-ray diffraction (GIXRD), scanning electron microscope (SEM), and UV–Vis spectroscope. The results reveal that a (EDA)(MA) 2 [Pb 3 I 10 ] film is more moisture resistant than a CH 3 NH 3 PbI 3 film which is widely used in the perovskite solar cell now. UV–Vis spectroscopy result also shows that the layered structure film is a suitable solar absorber with a bandgap (1.67 eV), which is close to the optimum value for solar photoelectric conversion. Compared to CH 3 NH 3 PbI 3 , the low-cost perovskite structure offers greater tunability on a molecular level for further material optimization and possibility for widely used in the future. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cell (SOFC) has been considered to generate power represented by conductivity. Zinc doped Barium Cerium Zirconium Yttrium oxide (BCZYZn) has been found to offer high protonic conductivity and high stability as being electrolyte for proton-conducting SOFCs. In this study, we report a new series of proton conducting materials, BaCe 0.7 Zr 0.25−x Y x Zn 0.05 O 3 (x = 0.05, 0.1, 0.15, 0.2 and 0.25). The materials were synthesized by solid state reaction route and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal expansion, particle size and impedance spectroscopy (IS). Rietveld analysis of the XRD data reveal a cubic perovskite structure with Pm-3m space group up to composition x = 0.15. For x = 0.15 and 0.20, the materials have structural phase change to orthorhombic in the Pbnm space group. Scanning electron microscopy images show high density materials. Thermal expansion measurements show that the thermal expansion coefficient is in the range 10.0–11.0 × 10 −6 /°C. Impedance spectroscopy shows higher ionic conduction under wet condition compared to dry condition. Y content of 25% (BCZYZn25) exhibits highest conductivity of 1.84 × 10 −2 S/cm in wet Argon. This study indicated that perovskite electrolyte BCZYZn is promising material for the next generation of intermediate temperature solid oxide fuel cells (IT-SOFCs). [ABSTRACT FROM AUTHOR]

The present research work reports the study on crystal structure, vibrational spectroscopy and thermal analysis of organic-inorganic hybrid compound (CH(CH)NH)CdCl. Single crystals of bis(phenethylammonium)tetrachlorocadmate (CH(CH)NH)CdCl (PEA-Cd) were obtained by diffusion at room temperature. This compound crystallizes in the orthorhombic space group C2cb with unit cell parameters a = 7.4444(2) Å, b = 38.8965(3) Å, c = 7.3737(2) Å and Z = 4. Single crystal structure has been solved and refined to R = 0.036 and wR = 0.092. The structure consists of an extended [CdCl] network and two [CH(CH)NH] cations to form a two-dimensional perovskite system. The infrared (IR) spectrum of the title compound was recorded at room temperature. Differential scanning calorimetry (DSC) was used to investigate the phase transition; this compound exhibits a reversible single solid-solid phase transition. [ABSTRACT FROM AUTHOR]

Partial substitution of cations and anions in perovskite-type materials is a powerful way to tune the desired properties. The systematic variation of the cations size, the partial exchange of O 2− for N 3− and their effect on the size of the optical band gap and the thermal stability was investigated here. The anionic substitution resulted in the formation of the orthorhombic perovskite-type oxynitrides Mg 0.25 Ca 0.65 Y 0.1 Ti(O,N) 3 , Ca 1- x Y x Zr(O,N) 3 , and Sr 1– x La x Zr(O,N) 3 . A two-step synthesis protocol was applied: i) (nano-crystalline) oxide precursors were synthesized by a Pechini method followed by ii) ammonolysis in flowing NH 3 at T = 773 K (Ti) and T = 1273 K (Zr), respectively. High-temperature synthesis of such oxide precursors by solid–state reaction generally resulted in phase separation of the different A -site cations. Changes of the crystal structures were investigated by Rietveld refinements of the powder XRD data, thermal stability by DSC/TG measurements in oxygen atmosphere, oxygen and nitrogen contents by O/N analysis using hot gas extraction technique, and optical band gaps by photoluminescence spectroscopy. By moving from Mg 0.25 Ca 0.65 Y 0.1 Ti(O,N) 3 via Ca 1– x Y x Zr(O,N) 3 to Sr 1– x La x Zr(O,N) 3 , the degree of tilting of the octahedral network is reduced, as observed by an increase in the B – X – B angles caused by the simultaneously increasing effective ionic radius of the A -site cation(s). In general, increasing substitution levels on the A -site (Y 3+ and La 3+ ) are accompanied by an enhanced replacement of O 2− by N 3− . In all three systems, this anionic substitution resulted in a reduction of the optical band gap by approximately 1 eV (Ti) and up to 2.1 eV (Zr) compared to the respective oxides. For Mg 0.25 Ca 0.65 Y 0.1 Ti(O,N) 3 an optical band gap of 2.2 eV was observed, appropriate for a solar water splitting photocatalyst. The Zr-based oxynitrides required a by a factor of 2 higher nitrogen contents to significantly reduce the optical band gap and the measured values of 2.9 eV–3.2 eV are larger compared to the Ti-based oxynitride. Bulk thermal stability was revealed up to T = 881 K. In general, the thermal stability decreased with increasing substitution levels due to an increasing deviation from the ideal anionic composition as demonstrated by O/N analysis. [ABSTRACT FROM AUTHOR]

SrTaO 2 N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr 1.4 Ta 0.6 O 2.73 , Ta 2 N, and Sr 5 Ta 4 O 15 . The second decomposition was not clearly observed when SrTaO 2 N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N 3− /O 2− . The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO 2 N perovskite lattice. LaTiO 2 N was confirmed to have a similar cis -configuration of the TiO 4 N 2 octahedron as that of TaO 4 N 2 in SrTaO 2 N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO 3 , La 2 O 3 , and TiN at 1100 °C. These temperatures are lower than those in SrTaO 2 N. [ABSTRACT FROM AUTHOR]

A new Os-based B-site ordered double perovskite with the chemical composition of Ca2ScOsO6 was successfully synthesized. The crystal structure of the title compound was determined by employing the powder X-ray diffraction method and was found to crystallize in the monoclinic P21/n space group with the cell constants of a = 5.4716(1) Å, b = 5.6165(1) Å, c = 7.8168 (1) Å, and β = 89.889 (2)°. The temperature-dependent magnetic susceptibility data suggest that this novel S = 3/2 compound undergoes an antiferromagnetic transition at ~69 K. Fitting the high-temperature susceptibility data (100-300 K) to Currie-Weisse behavior showed C = 1.734 emu·K/mol (μeff = 3.72 bohr magnetons) and = -341 K, which is indicative of dominant antiferromagnetic interactions. Temperature-dependent specific heat measurements exhibit a shape anomaly at 69 K, which is consistent with a long-range ordering of the spins. Because of a triangular arrangement of antiferromagnetically ordered magnetic ions, the system exhibits some degree of geometric magnetic frustration (GMF), but not strongly. Spin-dimer analysis, employing extended Hückel theory, reveals that a dominant exchange interaction exists (along the a crystallographic axis in perovskite layer), which violates the perfect condition for GMF. [ABSTRACT FROM AUTHOR]

The synthesis of previously unknown perovskite (CH3NH3)2PdCl4 is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic-inorganic layered Pd-based perovskites was still formed. This demonstrates that Pd-based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance-factor formula. The (CH3NH3)2PdCl4 phase has a bulk resistivity of 1.4 Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 104 cm−1. XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic-inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic-inorganic perovskites, the synthesis of this new Pd-based organic-inorganic perovskite may be helpful in the preparation and understanding of other organic-inorganic perovskites. [ABSTRACT FROM AUTHOR]

Single phase LaYbO3 lanthanide-based perovskite powder was synthesized by modified Pechini method, which is based on polyesterification of metal-citrate complexes in aqueous solution. Complexes were formed in aqueous solution and after polyalcohol addition and slow water evaporation, bond formation is allowed and a macroscopic polymeric network was produced, where cations are embedded and uniformly distributed. Finally, through several pyrolysis steps, microcrystalline oxide particles were obtained. Structural characterization was performed by means the powder X-ray diffraction (XRD) technique. The obtained patterns were indexed and refined to reveal that the LaYbO3 simple perovskite crystallizes in an orthorhombic structure, belonging to the Pnma (#62) space group, with lattice constants a = 6.0327 Å, b = 8.4138 Å and c = 5.8307 Å. Studies of electron dispersive X-ray spectroscopy show that the LaYbO3 is free of impurities. Electric response was evaluated by electric polarization measurements as a function of applied electric fields. Obtained curves show evidence of a hysteretic behavior related with dielectric losses which are characteristics of insulator materials. From the saturation values of electric charge, the relative dielectric constant was determined to be 22.6. The magnetic behavior was examined by means of the curves of magnetic susceptibility as a function of temperature. The fit with the Curie equation is in agreement with a typical paramagnetic feature with effective magnetic moment = 4.9 B, which is close to the theoretical expected value from the Hund's rules. [ABSTRACT FROM AUTHOR]

In the present work, polycrystalline perovskites of R 0.6 Sr 0.4 MnO 3 nanocomposites (R=La, Nd, or Sm) were synthesized using the sol–gel method in the presence of citric acid and polyethylene glycol as chelating and structure directing agents respectively. The synthesized gel was calcined at 800 °C for 5 h. The XRD revealed that the obtained nanocrystalline R 0.6 Sr 0.4 MnO 3 is monoclinic crystal structure of space group (I2/a). TEM images showed that the prepared perovskites are homogeneous and uniform with particle sizes in a range 20–40 nm and the HR-TEM images and lattice fringes displayed the monoclinic structure. IV measurements showed that Nd 0.6 Sr 0.4 MnO 3 has semiconducting properties at room temperature. With applying low magnetic field, a transition from semiconductor behavior to Ohmic resistivity was observed. The static resistance of Nd 0.6 Sr 0.4 MnO 3 was calculated to be ~2.985 TΩ for semiconductor phase and the resistance increased 1000 times that gives rise to negative magnetoresistance (MR). The value of MR of Nd 0.6 Sr 0.4 MnO 3 equals to 99.84%, which leads to the use of these materials in fabrication of magnetic devices in the industrial scale. [ABSTRACT FROM AUTHOR]

The Li 2 SrTa 2(1− x ) Nb 2x O 7 ( x = 0–1.0) with layered-perovskite type structure were synthesized by conventional solid state reaction method. The X-ray diffraction reveals that all these compounds possess orthorhombic crystal structure with Cmcm space group. B-site bond strength and B-site octahedral distortion of these compounds were calculated using bond lengths obtained from Rietveld refinement. The dielectric constant ( ϵ r ) decreased from 24.2 to 15.2 with increase in the Nb concentration, which was due to decrease in dielectric polarizability of compound. The non-monotonic variation in quality factor ( Q × ƒ ) was observed with Nb concentration. This variation of quality factor was correlated with the B-site bond strength. The B-site octahedral distortion was found to increase with Nb content, which was the major factor for increase in temperature coefficient of resonant frequency ( τ f ) of these compounds. [ABSTRACT FROM AUTHOR]

Two new hybrid lead halides (H 2 BDA)[PbI 4 ] ( 1 ) (H 2 BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI 3 ] ( 2 ) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2 , respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2 , the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2 , respectively. [ABSTRACT FROM AUTHOR]

We synthesize CdMn7O12 and SrMn7-xFexO12 (x = 0, 0.08, and 0.5) perovskites under high pressure (6 GPa) and high temperature (1373-1573 K) conditions and investigate their structural, magnetic, dielectric, and ferroelectric properties. CdMn7O12 and SrMn7O12 are isostructural with CaMn7O12: space group R3̅ (No. 148), Z = 3, and lattice parameters a = 10.45508(2) Å and c = 6.33131(1) Å for CdMn7O12 and a = 10.49807(1) Å and c = 6.37985(1) Å for SrMn7O12 at 295 K. There is a structural phase transition at 493 K in CdMn7O12 and at 404 K in SrMn7O12 to a cubic structure (space group Im3̅), associated with charge ordering as found by the structural analysis and Mössbauer spectroscopy. SrMn6.5Fe0.5O12 crystallizes in space group Im3̅ at 295 K with a = 7.40766(2) Å and exhibits spin-glass magnetic properties below 34 K. There are two magnetic transitions in CdMn7O12 with the Néel temperatures TN2 = 33 K and TN1 = 88 K, and in SrMn7O12 with TN2 = 63 K and TN1 = 87 K. A field-induced transition is found in CdMn7O12 from about 65 kOe, and TN2 = 58 K at 90 kOe. No dielectric anomalies are found at TN1 and TN2 at 0 Oe in both compound, but CdMn7O12 exhibits small anomalies at TN1 and TN2 at 90 kOe. In pyroelectric current measurements, we observe large and broad peaks around magnetic phase transition temperatures in CdMn7O12, SrMn7O12, and SrMn6.5Fe0.5O12; we assign those peaks to extrinsic effects and compare our results with previously reported results on CaMn7O12. We also discuss general tendencies of the AMn7O12 perovskite family (A = Cd, Ca, Sr, and Pb). [ABSTRACT FROM AUTHOR]

A powdered La2CoMnO6 double perovskite was synthesized by the solid-state reaction method, and its crystal structure was investigated by (mode-crystallography) Rietveld analysis using X-ray and neutron powder diffraction data. La2CoMnO6 material is a monoclinic perovskite at room temperature, adopting the space group P21/n (a−a−b+), UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/, c≈ 2ap and Z = 2. The P21/n phase can be described effectively by three distortion modes (GM4+, X3+, X5+) of the Fm3̅m (a0a0a0) parent phase. The comparative study of the material and those in the Ln2CoMnO6 and Ln2NiMnO6 families has shown a general trend in nearly all the materials, has served to select a common direction in the sub-space spanned by X5+, tri-linearly coupled to the order parameters of the cubic to monoclinic first order phase transition. This direction has been used to parametrize the refinements and to perform reliable refinements in the high-temperature intermediate distorted trigonal phase, R3̅ (a−a−a−), for which only one effectively acting irrep has been deduced: GM5+, physically a tilt of the oxygen sharing octahedra of Co and Mn. Its temperature evolution up to the prototype cubic phase has been fitted in the framework of the Landau Theory of Phase Transitions, showing a behavior typical of a tricritical point. The low-temperature neutron powder diffraction data have served to solve the magnetic structure: three indistinguishable ferromagnetic models with the space groups P21/n and P2STACKABOVE′/ABOVEBELOW1/BELOW/STACK/n′ are proposed. [ABSTRACT FROM AUTHOR]

The perovskite K 0.85 Ba 0.15 TaO 3+0.075 nanocrystallites have been synthesized by mild hydrothermal method for the first time. The powder X-ray diffraction analysis indicates that the crystallographic structure is a primitive cubic, space group Pm-3m with a unit cell edge a =4.00 Å. Heavily Ba doped in K-site was achieved in the perovskite structure with excess oxygen to balance the charge. The chemical substitution changes the crystal structure and electronic structure of KTaO 3 , which has an impact on its polarization property and induce a ferroelectric phase. The temperature-dependent dielectric response from 300 K to 600 K and hysteresis loop at 300 K provide direct evidence for the ferroelectric character. Its Curie temperature has been obtained from relative dielectric and thermal analysis ( T C =460 K). [ABSTRACT FROM AUTHOR]

TlMO3 perovskites (M3+ = transition metals) are exceptional members of trivalent perovskite families because of the strong covalency of Tl3+–O bonds. Here we report on the synthesis, crystal structure and properties of TlCrO3 investigated by Mössbauer spectroscopy, specific heat, dc/ac magnetization and dielectric measurements. TlCrO3 perovskite is prepared under high pressure (6 GPa) and high temperature (1500 K) conditions. The crystal structure of TlCrO3 is refined using synchrotron X-ray powder diffraction data: space group Pnma (no. 62), Z = 4 and lattice parameters a = 5.40318(1) Å, b = 7.64699(1) Å and c = 5.30196(1) Å at 293 K. No structural phase transitions are found between 5 and 300 K. TlCrO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite chromite family, ACrO3 (A3+ = Sc, In, Y and La–Lu). The unit cell volume and Cr–O–Cr bond angles of TlCrO3 are close to those of DyCrO3; however, the Néel temperature of TlCrO3 (TN≈ 89 K) is much smaller than that of DyCrO3 and close to that of InCrO3. Isothermal magnetization studies show that TlCrO3 is a fully compensated antiferromagnet similar to ScCrO3 and InCrO3, but different from RCrO3 (R3+ = Y and La–Lu). Ac and dc magnetization measurements with a fine step of 0.2 K reveal the existence of two Néel temperatures with very close values at TN2 = 87.0 K and TN1 = 89.3 K. Magnetic anomalies near TN2 are suppressed by static magnetic fields and by 5% iron doping. [ABSTRACT FROM AUTHOR]

Four new double perovskites, SrLaMReO6 (M = Mg, Mn, Co, Ni) in which Re5+ (5d2) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P21/n structure type, which consists of alternately corner-shared octahedra of MO6 and ReO6. Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites. Bond valence sum calculations (BVS) suggest all M and Re ions are 2+ and 5+, respectively, and for the Mn-containing phase this is also supported by XANES measurements. All of the materials are paramagnetic at room-temperature and their Curie–Weiss temperatures are positive (except for Mg) indicating net ferromagnetic interactions. No evidence for long-range magnetic order is evident in the dc magnetic susceptibility and μSR measurements for SrLaMgReO6 to 2 K. The Mn-phase shows long-range order at TC = 190 K and neutron diffraction revealed a ferromagnetic structure with a refined net moment of ∼3.7μB. Both Co- and Ni-containing phases exhibit spin glass behavior at TG = 23 and 30 K, respectively, which is supported by neutron diffraction and a.c. susceptibility data. The structure and physical properties of these four new rhenium based ordered double perovskites are compared to the closely related “pillared perovskites”, La5Re3MO16, the isoelectronic Os6+ (5d2) double perovskite Sr2CoOsO6, and the Re6+ (5d1) double perovskites, Sr2MReO6, (M = Mg, Ca, Mn, Co, Ni). [ABSTRACT FROM AUTHOR]

In the course of an investigation to prepare the hypothetic new double perovskite La3Co2VO9 with Co2+ and V5+ in octahedral sites, we obtained the new simple perovskite LaCo0.71(1)V0.29(1)O2.97(3) as the main phase. The pure compound was then synthesized by the citrate decomposition method. The crystal structure was studied by X-ray (PXRD) and powder neutron diffraction (PND). Physical properties were characterized by X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and thermogravimetric analysis (TGA). Rietveld refinements were performed in the orthorhombic space group Pnma (#62). Refined cell parameters were a = 5.4762(2) Å, b = 7.7609(2) Å and c = 5.5122(1) Å. Magnetization measurements showed that this perovskite is an antiferromagnet with a Neel temperature of 15 K. At high T the magnetization follows the Curie–Weiss law corrected by temperature independent paramagnetism (TIP) showing an effective magnetic moment of 3.03μB well described by the contribution of Co2+ (HS), Co3+ (IS), V3+ and V4+ ions. The crystallographic formula was refined by PND and oxidation state distribution was determined by the combination of PND, XAS, TGA and magnetic measurements. [ABSTRACT FROM AUTHOR]

Structural investigations of single crystals of the complex perovskite Ba 4 (Ba 2 Nb 2 )O 11 synthesized by the cold crucible induction melting method were carried out in the present study. The material was studied in the as prepared, dry and hydrated states. In dry and as prepared state, based on the observations both in TEM and XRD, a body centered tetragonal (BCT) structure having the space group I4/mmm (no. 80) and cell dimensions a ≈ 8.75 Å and c ≈ 17.1 Å was proposed. In hydrated state a hexagonal structure having the space group P 6 ¯ m2 (no. 187) and cell dimensions a = 6.038 Å and c = 18.0383 Å was proposed. Contrary to previous observations, this sample showed considerable water uptake when compared to sample with the same composition prepared by solid state reaction technique. The thermogravimetric (TG) curve also indicated a phase transition during water uptake. [ABSTRACT FROM AUTHOR]