Concentration- and Temperature-Induced Phase Transitions in PrAlO3–SrTiO3 System

摘要

Single-phase mixed aluminates-titanates Pr1−xSrxAl1−xTixO3 (x = 0.1, 0.2, 0.3, 0.5, 0.7) with rhombohedral perovskite structure were prepared by solid-state reaction technique at 1823–1873 K. Morphotropic rhombohedral-to-cubic phase transition in Pr1−xSrxAl1−xTixO3 series is predicted to occur at x = 0.88. The temperature-induced structural phase transition R  3¯  с − Pm3¯  m in Pr0.5Sr0.5Al0.5Ti0.5O3, detected at 930 K by in situ high-temperature X-ray synchrotron powder diffraction, occurs at considerably lower temperature as the corresponding transformation in the parent compound PrAlO3 (1770 K). Such remarkable drop of the transition temperature is explained by gradual decrease of the perovskite structure deformation in the Pr_1−xSr_xAl_1−xTi_xO₃ series with increasing Sr and Ti contents as a consequence of the increasing Goldschmidt tolerance factor. For Pr_0.3Sr_0.7Al_0.3Ti_0.7O₃ phase, a sequence of the low-temperature phase transformation R  3¯  с − Immb(C2/m) − I4/mcm was detected.