The Effect of Sintering Atmosphere and Temperature on Densification, Grain Growth Behavior and Electrical Properties of 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Ceramics

(Na0.5Bi0.5)TiO3-BaTiO3-SrTiO3-based lead-free piezoelectric ceramics are one of the possible replacements for Pb(Zr1−xTix)O3. Although they are considered a promising alternative actuator material due to their large electric-field-induced strains, they have several drawbacks, such as large strain hysteresis and the requirement of a high electric field to obtain large electric-field-induced strains. Sintering parameters strongly influence the electrical properties. Thus, the effect of sintering parameters, including atmosphere (air/oxygen), temperature (1150 °C~1250 °C) and holding time (1~20 h) on the sintering behavior of 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 electroceramics was studied. Then, the influence of sintering atmosphere on the piezoelectric, ferroelectric and dielectric properties of 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 electroceramics sintered at 1250 °C for 1 h was investigated. Sintering in oxygen improves density and restrains grain growth including abnormal grain growth. 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 electroceramics sintered in oxygen exhibit smaller grain size, higher density, similar inverse piezoelectric coefficient d33* and lower strain hysteresis compared to air-sintered samples. The effect of sintering atmosphere on grain growth is explained using the mixed control mechanism of boundary migration.