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

Abstract

Metathetic solid-state reactions of alkaline earth perovskite zirconates (AZrO₃, A = Ca, Sr, Ba) and lead sulfate (PbSO₄) result in the relatively quick formation of perovskite PbZrO₃ and the corresponding alkaline earth sulfate ASO₄ 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 µm) PbZrO₃ powders starting from inexpensive precursors. In all the reactions, we believe the driving force to be the high enthalpy of formation of ASO₄ 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.