摘要
The perovskite oxide La_ 1-xSr_xCoO_3 ( 0≤x≤0.5) series were prepared under different sintering conditions. Crystal structure was determined by powder X-ray diffraction and lattice parameters as a function of Sr-concentration x were obtained by using Rietveld method. The dc resistivity investigated in the temperature range of 80～300 K indicates that the electric properties exhibit a metallic-insulator (semiconducting) (M-I) transition for 0.2<x<0.3. The samples with x=0.2 is close to the M-I transition boundary. The influence of sintering conditions on the lattice parameters, resistivity and the ferromagnetic phase transition temperature T_C of La_ 1-xSr_xCoO_3 for the cases x=0.2 and 0.5 was discussed. The change of the electric properties of semiconductor-like sample (x=0.2) with sintering temperature and sintering period is just opposite to that of metallic sample (x=0.5). Annealing in flowing oxygen can decrease the resistivity of semiconductor-like sample.
The perovskite oxide La_ 1-xSr_xCoO_3 ( 0≤x≤0.5) series were prepared under different sintering conditions. Crystal structure was determined by powder X-ray diffraction and lattice parameters as a function of Sr-concentration x were obtained by using Rietveld method. The dc resistivity investigated in the temperature range of 80～300 K indicates that the electric properties exhibit a metallic-insulator (semiconducting) (M-I) transition for 0.2<x<0.3. The samples with x=0.2 is close to the M-I transition boundary. The influence of sintering conditions on the lattice parameters, resistivity and the ferromagnetic phase transition temperature T_C of La_ 1-xSr_xCoO_3 for the cases x=0.2 and 0.5 was discussed. The change of the electric properties of semiconductor-like sample (x=0.2) with sintering temperature and sintering period is just opposite to that of metallic sample (x=0.5). Annealing in flowing oxygen can decrease the resistivity of semiconductor-like sample.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina(10225417)andtheNaturalScienceFoundationofZhejiangProvince(R104265)
