Extrinsic and intrinsic contributions to the electrostrain in precipitation-hardened barium calcium titanate

Deconvoluting the extrinsic and intrinsic contributions to electrostrain is of great importance to understand the hardening mechanism of piezoceramics. Here, in situ electric-field high-energy x-ray diffraction measurements are performed to investigate the polycrystalline barium calcium titanate hardened by precipitation, a recently developed hardening technique that pins domain walls with fine intragranular precipitates. The effect of precipitates on extrinsic and intrinsic mechanisms is examined. Under a low-frequency and large-signal field, the precipitates suppress non-180° wall motion, which is the major source of loss, by 40%. Anisotropy is observed in the field-induced lattice strain, which is dominantly contributed by an intergranular effect instead of pure piezoelectricity. At small fields, the lattice strain is barely affected by precipitates, while both lattice strain and strain from non-180° domain wall motion are suppressed and are coupled with each other at large fields, leading to an unchanged relative percentage of the extrinsic contribution.