Evolution of crystallographic phases in (Sr1-xCax)TiO3 with composition (x)

Results of X-ray powder diffraction, neutron powder diffraction, electron m icrodiffraction, and convergent beam electron diffraction (CBED) studies ar e presented to show that the space group of (Sr1-xCax)TiO3 (SCT) in the com position range 0.35 < x less than or equal to 0.55 cannot be Cmcm. The corr ect space groups are Pbcm for 0.35 < x less than or equal to 0.40 and Pbnm for 0.40 < x less than or equal to 0.55. The analysis of powder XRD data re veals that the structure of SCT is noncubic for x greater than or equal to 0.06. It is shown that four different types of orthorhombic phases appear i n the SCT system with increasing Ca2+ content. (C) 2001 Academic Press.