Elastic anomalies associated with transformation sequences in perovskites: II. The strontium zirconate-titanate Sr(Zr, Ti)O3 solid solution series

The sequence of phase transitions due to octahedral tilting across the Sr(Zr, Ti)O-3 solid solution series has been investigated by resonant ultrasound spectroscopy at high and low temperatures using ceramic samples. The elastic behaviour associated with phase transitions as a function of composition in Sr( Zr, Ti) O-3 at room temperature is proposed to be analogous to that as a function of temperature in SrZrO3, with the Pnma <-> Imma transition at SrZr0.57Ti0.43O3, Imma <-> 14/mcm at SrZr0.35Ti0.65O3, and 14/mcm <-> Pm (3) over barm at SrZr0.05Ti0.95O3. Changes in elastic constants and acoustic dissipation with temperature have been analysed for samples across the compositional range. The intermediate phases, 14/mcm and what is assumed to be Imma, appear to have stability fields across the full compositional range and both show large dissipation effects, most probably due to twin wall mobility. In contrast, the Zr-rich Pnma phase, which should contain transformation twin walls, is an unexpectedly stiff and non-dissipating material, similar to the high temperature and/or Ti-rich Pm (3) over barm phase. In the case of Pnma, this is attributed to coupling between the two order parameters, which could impede relaxation responses to an applied stress. The Pm (3) over barm structure is a classically stiff cubic perovskite and no transformation-related dissipation processes are expected.