Preparation of PbZrO3/ASO4 composites (A = Ca, Sr, Ba) and PbZrO3 by metathetic reactions in the solid state:: Metathetic exchange of divalent species

Metathetic solid-state reactions of alkaline earth perovskite zirconates (AZrO(3), A = Ca, Sr, Ba) and lead sulfate (PbSO4) result in the relatively quick formation of perovskite PbZrO3 and the corresponding alkaline earth sulfate ASO(4) at temperatures as low as 1023 K. The product can be described as a composite dispersion of small (<300 nm) particles of PbZrO3 on larger crystals of the alkaline earth sulfates. The solid-state reaction at 973 K between ZrO2, PbSO4, and K2CO3 followed by washing in water to remove K2SO4 provides a quick route to submicron (< 1 mum) PbZrO3 powders starting from inexpensive precursors. In all the reactions, we believe the driving force to be the high enthalpy of formation of ASO(4) or K2SO4. The reactions presented here provide proof of concept for the preparation of a number of important polar lead-based perovskite phases under relatively mild conditions: (i) as composites, (ii) as small particles, and (iii) possibly as porous monoliths.