Leaching kinetics and chemical stability of complex perovskite solid solutions

Piezoelectric perovskites are increasingly studied for applications in aqueous environments such as catalysts or biomedical implants. This necessitates a clarification of their leaching kinetics, as many perovskites have been identified as thermodynamically unstable in water. Many piezoelectric perovskites with desirable functional properties have complex chemical compositions, which makes the prediction of leaching kinetics challenging. In the present study, we elucidate the leaching behaviour of Bi 0.5 Na 0.5 TiO 3 -BaTiO 3 (BNT-6BT) ceramic powders in acidic aqueous media over a duration of 31 days. The combination of an Unreacted Shrinking Core (USC) model with experimental validation revealed the importance of the specific bonding environment beyond the general perovskite structure to the leaching kinetics of the different elements. The presence of the stereochemically active lone pair of Bi 3 + is discussed as the origin of the differences in dissolution properties compared to other perovskite piezoelectrics. Since the presented USC model effectively predicts perovskite leaching kinetics it provides a useful tool to screen for suitable material compositions for applications in aqueous media. • Leaching kinetics of BNT-6BT perovskite ceramics in acidic aqueous environments can be predicted using a Unreacted Shrinking Core model. • The leaching behavior is strongly influenced by the bonding environment, particularly the stereochemically active lone pair on Bi 3 + . • Effective coordination numbers provide more accurate predictions of leaching behavior than idealized perovskite structures. • Ba 2 + shows consistent leaching kinetics across both simple and complex perovskite matrices. • The retention of Bi 3 + in the depletion layer suggests preserved non-centrosymmetry and potential maintenance of piezoelectric properties after aqueous exposure.