Large enhancement of piezoelectric properties in Mn-modified SrBi4Ti4O15 and its thermal stabilities at elevated temperatures

Manganese-modified strontium bismuth titanate (SrBi4Ti4O15, SBT) ceramic oxides were synthesized by substituting a small amount of manganese ions into the Ti4+ sites using conventional solid-state reaction. The resultant Mn-modified SBT (SBT-Mn) exhibits better piezoelectric properties in comparison to unmodified SBT. The piezoelectric properties of Mn-modified SBT is optimized with only 4 mol% Mn substitution. SBT-4Mn exhibits a large piezoelectric constant (d33=30 pC/N), approximately twice the value of unmodified SBT (d33=13 pC/N), while its Curie temperature, Tc, remains almost unchanged at ~530 °C. The temperature-dependent electrical impedance and electromechanical coupling factors kp and kt reveal that the SBT-4Mn exhibits thermally stable electromechanical coupling characteristics up to 300 °C but electromechanical coupling factors deteriorate significantly at a higher temperature due to increased conductivity. Our work suggested that Mn-modified SBT ceramics are promising materials for high temperature piezoelectric applications.