Grain size effect on electrical properties of Mn-modified 0.67BiFeO3-0.33BaTiO3 lead-free piezoelectric ceramics

To investigate how grain size affects the dielectric, ferroelectric, and piezoelectric properties of Mn-modified 0.67BiFeO(3)-0.33BaTiO(3) ceramics, we prepared samples with a wide variety of grain sizes from 4.1 mu m to 0.59 mu m via a conventional solid-state process that use the normal and the two-step sintering methods. Small-signal dielectric measurements show that all the samples exhibit a relaxor-like behavior and that grain size has little influence on the room-temperature dielectric permittivity. For grain sizes below 2 mu m, the remanent polarization P-r and piezoelectric coefficient d(33) decrease with the grain size, whereas they remain almost constant near P-r = 27 mu C/cm(2) and d(33) = 70 pC/N in samples with grain sizes exceeding 2 mu m. The mechanism underlying the observed grain size effect is discussed in terms of the electric-field-induced formation of macroscopic ferroelectric domains. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.