Evolution of crystallographic phases in (Sr_(1-x)Ca_x)TiO_3 with composition (x)

摘要

Results of X-ray powder diffraction,neutron powder diffraction, electron microdiffraction, and convergent beam electron diffraction (CBED) studies are presented to show that space group of (Sr_(1-x)Ca_x)TiO_3 (SCT) in the composition range 0.35< x < 0.55 cannot be Cmcm. The correct space groups are pbcm for 0.35 < x <0.40 and Pbnm for 0.40 < x < 0.55. The analysis of powder XRD data reveals that the structure of SCT is noncubic for x >= 0.06. It is shown that four different types of orthorhombic phases appear in the SCT system with increasing Ca~(2+) content.