Novel Features of Sr_1−xCa_xTiO₃ Phase Diagram: Evidence for Competing Antiferroelectric and Ferroelectric Interactions

Abstract

Structural and dielectric evidences are advanced to show that the Sr_1−xCa_xTiO₃(SCT) system undergoes an antiferroelectric (AFE) phase transition in the composition range 0.18≤x≤0.40. Stabilization of the AFE phase, instead of the ferroelectric (FE) phase known for 0<x<0.12 , is shown to be intimately linked with the nonpolar antiferrodistortive phase transitions driven by the R and M point instabilities preceding the AFE transition. It is proposed that the disorder and frustration introduced by CaTiO₃ substitution in the incipient FE matrix of SrTiO₃ leads to the smearing of the ɛ ′(T) response in SCT for 0.002 <x<0.12 akin to dipole glasses and relaxor ferroelectrics.