A Unified Framework for Grain‐Size‐Mediated Piezoelectric and Electromechanical Properties of Barium Titanate Ceramics

ABSTRACT This study presents a framework to analyze the grain‐size effect in BaTiO 3 ceramics by correlating domain wall (DW) density and lattice distortion at the DW. BaTiO 3 ceramics with average grain size (GS) of 0.9–10 µm were fabricated via conventional and two‐step sintering methods. Following DC poling of 3 kV/mm at 80°C, the piezoelectric charge constant ( d 33 ) showed a maximum of 440 pC/N at GS of 1.2 µm, due to an optimum DW density and lattice distortion at the DW. Both smaller and larger GSs relative to 1.2 µm showed a decrease in d 33 , attributed to reduced lattice distortion at the DW for smaller grains and decreased DW density for coarse grains. A similar trend was observed in the dielectric constant, free permittivity, coupling coefficient, elastic compliance, and piezoelectric voltage coefficient. Furthermore, the mechanical quality factor ( Q m ) evaluation revealed intrinsic and extrinsic contributions, with a maximum Q m of 140 at GS = 10 µm. This framework provides a unified explanation for the grain‐size‐dependent electromechanical properties of BaTiO 3 ceramics.