Influences of sintering aids on discontinuous grain growth and properties in BaTiO3-based ferroelectric ceramics

This work studies the influences of sintering aids on discontinuous grain growth (DGG) and corresponding grain size effect in Ba(Ti_0.8Zr_0.2)O₃ ceramic. When sintering temperature (T_S) is 1280–1340°C, the DGG phenomenon is observed with little change in phase structure, and grains all grow from several to tens of micrometers. Adding LiF can decrease the temperature span (T_span) of DGG from 20°C to 10°C due to the high mobility of Li⁺; however, adding Li₂CO₃ extends T_span from 20°C to 40°C since it decomposes and releases gas and then hinders the DGG process. Adding SiO₂ and B₂O₃ decreases the critical T_S of DGG by about 20–30°C due to their lower melting point or eutectic temperature. A higher critical T_S or a narrower T_span generally results in smaller grains and lower density before DGG, while can induce larger grains and higher dielectric/ferroelectric properties after DGG. Obvious dielectric diffuseness behavior is observed after adding Li₂CO₃ or B₂O₃ due to the smaller grains or more pores. The variation in properties is consistent with the grain size change after adding sintering aids. This work shows a fundamental understanding of sintering aids' influences on DGG and provides guidance for controlling microstructure and properties in polycrystalline ceramics.