Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re...Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.展开更多
New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7）...New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7） are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4021-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4021-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y（2） site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above -175 K for the two compounds.展开更多
The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and parti...The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.展开更多
文摘Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50872148 and 51072225)the National Basic Research Program of China (Grant No. 2007CB925003)
文摘New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7） are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4021-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4021-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y（2） site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above -175 K for the two compounds.
文摘The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.
