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A series of CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ white phosphors were prepared by high temperature solid phase method. The structure and phase purity of representative samples were characterized by Rietveld refinement and Fourier transform infrared spectrum. In CaY 1.97 Al 4 SiO 12 : 0.03Dy3+ phosphors, the sample has two characteristic peaks at 485 nm (4F 9/2 →6H 15/2) and 574 nm (4F 9/2 →6H 13/2) excited at 350 nm. In CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ phosphors, the luminescence intensity of CaY 1.97 Al 4 SiO 12 : 0.03Dy3+ samples were significantly improved by partially substituting Y3+ in the host with Gd3+, showing strong white luminescence. The reasons for enhanced luminescence after partial substitution of Gd3+ are discussed in detail from the perspective of phosphor structure and crystal field effect around Dy3+. In addition, with the substitution of Gd3+, the sample showed low thermal quenching, which was illustrated by combining the calculation of Debye temperature and activation energy. Finally, the chromaticity coordinates of CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ phosphors were all located in the white region, and combined with the 310 nm chip package, white phosphors with high color rendering index were obtained. Therefore, CaY 1.93 Al 4 SiO 12 : 0.03Dy3+, 0.04Gd3+ phosphors can be used as high-quality materials in the field of w-LED. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Nd 0.5 R 0.5 FeO 3 (R = La, Pr and Sm) synthesized by sol-gel combustion method have been investigated for their structural, optical, thermal and magnetic properties. X-ray diffraction in combination with Fourier transform infrared (FTIR) spectra confirm the single-phase orthorhombic structure with Pbnm space group of all the samples. Rietveld refinement employed to determine the bond lengths (Fe–O, R–O) and bond angles (Fe–O–Fe) show a decrease in the bond angle with Sm doping. Transmission electron microscopy (TEM) micrographs reveal the nano-size particles and selected area electron diffraction (SAED) patterns indicate good crystallinity with a uniform distribution of particles throughout the samples. Raman spectra clearly indicate the compressive strain in the Sm doped sample that has been correlated with the structural parameters obtained from Rietveld refinement. The shift in wavenumber is the main cause of change in bond length (Fe–O) and tilt of octahedra due to rare earth ions. The optical bandgap is determined using Tauc's relation from the diffuse reflectance spectra. The variation of specific heat has been investigated with temperature in a broad temperature range. The endothermic peak in specific heat has been correlated with magnetic order. The value of Néel temperature increases in the case of La-doped sample and reduces for the Pr doping. However, the decrease of specific heat in Sm doped sample around 300 °C may be attributed due to the spin reorientation. Magnetic studies at room temperature reveal antiferromagnetic behavior with weak ferromagnetic component due to the canted ordering of Fe3+ spins. Magnetic properties are strongly dependent on the type of rare earth ion as the maximum magnetization (M m) is enhanced from 0.259 to 0.434 emu/g with the doping of rare earth ions (La, Pr and Sm). The increase in magnetization has been correlated with increased distortion which is evident from the decrease in the bond angle. Exchange bias (EB) effect is observed for all samples as single-phase orthorhombic structure is composed of antiferromagnetic (AFM) and ferromagnetic (FM) phases. • Nd 0.5 R 0.5 FeO 3 (R = La, Pr, and Sm) have been successfully synthesized using sol-gel auto-combustion route. • Fe–O–Fe bond angle is found to decrease from on doping with different rare earth ions. • Room temperature magnetic hysteresis loops show the antiferromagnetic behavior with weak ferromagnetism. • Neel temperature is found to increase in case of La doped sample and decreases in case of Pr doped sample. [ABSTRACT FROM AUTHOR]

Abstract The thermoelectric transport properties of artificially textured polycrystalline CrSiTe 3 samples have been investigated for elucidating their correlations with a crystal structure and the corresponding charge density distribution. We verified that the low mobility of 13–27 cm2 V−1 s−1 attributing poor electronic transport properties is originated from the discrete charge density distribution in the covalently bonded layer. Also, the modulation of thermal conductivity values from 3.5 to 5.4 W m−1 K−1 with varying the texture was confirmed in pristine CrSiTe 3. Thus, we suggest that the electronic and thermal transport properties of layer structured CrSiTe 3 are strongly correlated with crystallographic features. Graphical abstract Image 1 Highlights • Thermoelectric transport properties of CrSiTe 3 compounds. • Strong correlation between structure and thermoelectric properties. • The charge density distributions are strongly localized without no overlaps. • In-plane electronic transport properties depend on charge density distributions. • Anisotropy in thermal conductivity inherited from crystal structure. [ABSTRACT FROM AUTHOR]

A series of phosphosilicate phosphors Sr 8 La 2 (PO 4 ) 3.5 (SiO 4 ) 2 (BO 4 ) 0.5 BO 2 : Ce 3+ , Tb 3+ are synthesized by solid-state reaction for the first time. The XRD Rietveld refinement presents that the compound crystallizes in a trigonal crystal system with space group P 3 ¯ (No. 147). Under the excitation of 340 nm, commonly blue and yellowish green emissions from Ce 3+ and Tb 3+ are detected and can generate the color-tunable light with chromaticity coordinates from (0.188, 0.095) to (0.351, 0.517) by changing the ratio of Ce 3+ /Tb 3+ . By the photoluminescence spectra, decay times and energy transfer efficiency, the mechanism of energy transfer between Ce 3+ and Tb 3+ has been carefully investigated. With the increase of temperature, the Ce 3+ or Tb 3+ single doped sample shows an excellent thermal property, but when the Ce 3+ and Tb 3+ are co-doped into the host, the thermal property of sample seriously degenerates. This result indicates that the change of temperature can affect the energy transfer between Ce 3+ and Tb 3+ strongly and based on the configurational coordinate diagram, this phenomenon is explained reasonably. [ABSTRACT FROM AUTHOR]

Abstract: A new K3Bi2(NO3)9 phase was discovered at a synthesis of Bi-containing photocatalysts. K3Bi2(NO3)9 has cubic structure with unit cell parameter a =13.5354(20)Å, and belongs to P4332 (No. 212) space group. New phase is isostructural with the K3 Ln 2(NO3)9 (Ln =La, Ce, Pr, Nd, and Sm) phases. The crystal structure was refined from powder X-ray diffraction (XRD) data. The R wp factor at Rietveld refinement was equal to 8.62%. The morphology of K3Bi2(NO3)9 was characterized using scanning electron microscopy. The value of ionic radius of Bi3+ in 12-fold coordination calculated from the unit cell parameter was found to be 1.314(5)Å. K3Bi2(NO3)9 phase and products of its thermal decomposition were studied using XRD, Fourier transform infrared spectroscopy (FTIR) methods and thermal gravimetric analysis (TGA). At 350°C, K3Bi2(NO3)9 phase was transformed to new unknown intermediate bismuth potassium nitrate that most likely belongs to Sillen type of structure. Geometrical solution for unit cell of this phase was proposed. [Copyright &y& Elsevier]

Abstract: The thermal expansion and stability of predominantly single-phase Ti2SC powders in argon and air was investigated by Rietveld analysis of synchrotron X–ray diffraction spectra. When the sample was heated in an Ar atmosphere, it started to dissociate into TiS2 (see footnote 1) at ≈400°C. At 8.5 (5)×10−6 °C−1 and 8.8 (2)×10−6 °C−1 the thermal expansion coefficients along the a and c-directions, respectively, are quite similar. The volumetric thermal expansion is 25.2 (5)×10−6 °C−1. When Ti2SC was heated in air, it started to oxidize, at 400°C, first to anatase, which converts, at higher temperatures, to rutile. The sulfur and carbon atoms presumably diffuse outward and escape as gases. [Copyright &y& Elsevier]

• The effect of Mn additions on the structural and magnetic properties of AlCoCrFeNi was studied. • The arc-melted alloys consisted of a mixture of B2 and bcc phases, the relative amount of which was dependent on Mn content. • Gas atomised powders were single phase with the B2 structure. • Mn additions increased saturation magnetisation but lowered the magnetic transition temperature and the thermal stability. ga1 Alloys of AlCoCrFeMn x Ni (x = 0.0, 0.04, 0.08, 0.12 and 0.16) have been synthesized through arc–melting and gas atomisation (x = 0.0 and 0.16) to investigate the effect of Mn additions to AlCoCrFeNi. Here, the structure, magnetic properties and the thermal stability of the alloys is presented. Electron microscopy confirmed the elemental composition and revealed the microstructure to consist of two spinodally decomposed phases. Rietveld analysis of standard powder X-ray diffraction showed the arc-melted samples consisted of two phases, a B2 phase and a bcc phase while the gas atomised powders consisted of a single-phased B2 structure. Magnetic measurements revealed an increase in the saturation magnetisation at room temperature by 68% for AlCoCrFeMnNi compared to AlCoCrFeNi. The thermal stability of the alloys was investigated using magnetometry, differential scanning calorimetry and in–situ X-ray diffraction, which showed that an increase in Mn content adversely effected the thermal stability of the alloy. [ABSTRACT FROM AUTHOR]

The single-phase Ba 3 Sc(BO 3) 3 :Ce3+/Tb3+ samples were synthetized via high-temperature solid-state reaction. X-ray diffraction (XRD), Rietveld refinement and transmission electron microscopy (TEM) were used for characterizing the morphology and phase purity of Ba 3 Sc(BO 3) 3. The photoluminescence emission (PL) and excitation (PLE) spectra, lifetime decay behavior and thermal stability of the Ba 3 Sc(BO 3) 3 :Ce3+/Tb3+ phosphors were discussed in detail. Site occupation of Ce3+ ions in Ba2+ and Sc3+ sites were explained through Gaussian fitting and Van Uitert empirical equation. All these properties are closely related to the intrinsic crystallization structure of the Ba 3 Sc(BO 3) 3 matrix, which is discussed in detail in this paper. Compared with Ba 3 Sc(BO 3) 3 :1%Tb3+ sample, the luminous intensity of Tb3+ increased about 3.2 and 4.1 times for Ba 3 Sc(BO 3) 3 :2%Ce3+,1%Tb3+ monitored at 342 and 313 nm, respectively. Energy transfer (ET) mechanism of Ce3+→Tb3+ were dipole-dipole interactions and quadrupole-quadrupole interactions at Ce3+(1) and Ce3+(2) sites, respectively. The temperature-dependent PL spectra of Ba 3 Sc(BO 3) 3 : Ce3+,Tb3+ illustrated that this phosphor possesses excellent thermal stability and chromaticity stability. Finally, a white LED device was prepared via the combination of the n-UV chip (365 nm), commercial blue BAM:Eu2+ phosphor, green Ba 3 Sc(BO 3) 3 :2%Ce3+,6%Tb3+ phosphor and commercial red Sr 2 Si 5 N 8 :Eu2+ phosphor, which showed bright warm-white light. These conclusions proved that the green Ba 3 Sc(BO 3) 3 :2%Ce3+,6%Tb3+ phosphor is desirable for white LED applications. • Ce3+ ions occupied at Ba and Sc3+ sites for Ba 3 Sc(BO 3) 3 :Ce3+ emit blue light. • Broader absorption band (200–400 nm) matches well with the n-UV LED chips. • Decay curves prove the existence of multiple sites energy transfer of Ce3+.→Tb3+. • Color tuning from blue to green is successfully realized by the energy transfer. • Luminous intensity and thermal stability are increase. [ABSTRACT FROM AUTHOR]