Experimental verification of the ab initio phase transition sequence in SrZrO3 and comparisons with SrHfO3 and SrSnO 3

Abstract

We present detailed Raman studies of SrZrO3 (SZO) that show three anomalies in Raman modes: One has a small jump in frequency ω, one has its intensity vanish, and a third has a sharp change in temperature derivative dω(T)/dT from flat below T = 600 K to a Curie-Weiss dependence above 600 K with extrapolation to zero frequency at the known transition temperature T = 970 K, thereby proving the latter to be displacive. In addition, the P4mm ferroelectric phase predicted at high stresses has preliminary support from polarization-voltage experiments. The inference of a new transition in the temperature region 600-650 K is in disagreement with neutron studies. Comparisons are given for family member SrSnO3 and SrHfO3, and we discuss the different conclusions of Kennedy and Knight. We show that a known transition in SrHfO3 is also displacive with a well-behaved soft mode.