Incipient piezoelectrics and electrostriction behavior in Sn-doped Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics

Dielectric, ferroelectric, piezoelectric, and strain properties of lead-free Sn-doped Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) were investigated. A crossover from a nonergodic relaxor to an ergodic relaxor state at room temperature, accompanied by a giant electric-field-induced strain, was observed at 5 at. % Sn doping. Switching dynamics monitored during a bipolar poling cycle manifested that the observed giant strain originates from incipient piezoelectricity. When Sn doping level reached 8 at. %, BNKT exhibited an electrostrictive behavior with a highly temperature-insensitive electrostrictive coefficient of Q11 = 0.023 m4 C−2.