Piezoelectric properties of Mn-doped (Na0.5Bi0.5)0.92Ba0.08TiO3 ceramics

Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.08TiO3+x mol.% Mn (BNBT-Mn) with x ranging from 0 to 2.97 are synthesized by conventional solid state reaction. The sintered BNBT-Mn exhibited a single phase perovskite structure without detectable secondary phase from x=0 to x=2.6. With increasing amount of doped Mn, the Curie temperature (Tc) of BNBT-Mn decreased rapidly, piezoelectric constants d33 and kt increased promptly when x was lower than 0.56, taking the maximum value of 160×(10−12 C/N) and 58.5%, respectively for x=0.56, then decreased slightly with x ranging from 0.56 to 2.6, and finally decreased rapidly for x>2.6, whereas Qm showed a different trend from d33 and kt. Furthermore, kt had a relatively high value under the low poling field (Ep) for x=0.56 owing to the reduced coercive field (Ec). Possible mechanisms of the influence of Mn doping on the microstructure and piezoelectric properties are discussed.