CaTiO₃-rich precipitates and their impacts on ferroelectric domains during heating in (Ba,Ca)TiO₃ ceramics

Precipitates have been shown to harden bulk piezoelectric ceramics, manifested as their increased mechanical quality factor. In this work with a model system (Ba,Ca)TiO₃, we analyze the morphologies of CaTiO₃-rich precipitates and their impacts on the microstructures in their surrounding BaTiO₃-rich matrix. Also, the response of ferroelectric domains around CaTiO₃-rich precipitates during heating and cooling is observed in situ with transmission electron microscopy. Domains attached to precipitates are observed remaining unchanged up to the Curie point at which they disappear. During cooling, domains are observed to form in the vicinity of precipitates and being held in place down to room temperature. Both observations corroborate previous findings that precipitates act as domain-pinning points, behaving in a similar manner to earlier experiments with electrical field biasing. Dislocations are often seen around precipitates in the matrix grain and are observed interfering with domains during heating cycles. Dislocations may provide an additional mechanism to restrict domain wall motion and offer a greater piezoelectric hardening effect.