Micro-Raman study of perovskites in the CaTiO3–SrTiO3 system

Abstract

The perovskite compounds Ca_{1 − x}Sr_xTiO₃ (0 ≤ x ≤ 1) have been studied by Raman spectrometry at room temperature. Following the intensity of selected bands, we have confirmed the sequence of phase transitions with increasing Sr content from orthorhombic Pbnm through tetragonal I4/mcm to cubic, and the phase boundaries have been located near x = 0.67 and x = 0.95, respectively. The Raman spectra gave no indication of a Bmmb structure. With increasing x, all the Raman modes shift to lower frequency, the shift being more pronounced in the low frequency bands. These frequency shifts have been related to structural information obtained from X-ray diffractometry. Linear relationships are observed between the behaviour of structural parameters, such as the Ca(Sr)–O distance and the octahedral tilt angle, and the corresponding Raman frequency shifts.