Crystal structure and metal-insulator transition of La1-xSrxCoO3

Crystal structure of perovskite La1-xSrxCoO3(0.0 less than or equal to x less than or equal to 0.7) was precisely determined by powder X-ray Rietveld analysis, and its correlation with the electrical properties was discussed. The space group was assigned to rhombohedral R(3) over barc$ in the range 0.0 less than or equal to x less than or equal to 0.5 and to cubic Pm3m in the range 0.55 less than or equal to x less than or equal to 0.7. At x similar to 0.25 the Co-O distance and Co-O-Co angle of this system showed an abrupt decrease and increase with increasing x, respectively, and the conductivity behavior changed from semiconducting to metallic. The abrupt changes in crystal structure were attributed to a change in the band structure at the transition from semiconducting to metallic, that is, an increase in the overlap between the valence band and doped hole sates. (C) 1996 Academic Press, Inc.