Effect of Mn dopant on the grain size and electrical properties of (Ba, Sr)TiO₃ ceramics

Doping can adjust the grain size of ferroelectrics and also affects the electrical properties of ferroelectrics. In this study, the grain size effect induced by doping on the aging of lead-free (Ba_0.8Sr_0.2)(Ti_1−xMn_x)O₃ ferroelectric ceramics was investigated. The changing of the grain size was realized by doping different content of Mn ions (x = 1.0–4.0 mol%) without inducing secondary phase. The result showed that higher Mn dopant decreases the grain size and changes the aging behaviour correspondingly. The building up of the internal bias field E _i , which was derivative from the hysteresis loop, is relatively faster and larger when Mn content is higher than 2.0 mol%. The E _i saturates earlier when Mn content is higher than 2.0 mol%. The interesting aging effect in the high Mn doped samples is considered mainly due to the obvious decreasing of grain sizes induced from Mn dopants. The piezoelectric properties increases first and then decreases with the Mn content increasing. The piezoelectric properties reaches the peak value at x = 2.0 mol%, being attributed to a dual role of the Mn dopant on increasing the internal bias field but decreasing grain size. This study is helpful to control the aging effect and improve the electrical properties through dopants and adjusting grain sizes.