Enhanced piezoelectric property and promoted depolarization temperature in Fe doped Bi1/2(Na0.8K0.2)1/2TiO3 lead-free ceramics

Piezoelectric sensors and energy harvesters require piezoelectric materials with large piezoelectric responses and good thermal stability. However, a commonly accepted concept is that the promotion of depolarization temperature of Bi1/2Na1/2TiO3-based lead-free ceramics is usually companied by deterioration of piezoelectric properties. In the present study, the effects of acceptor-Fe doping on piezoelectric property and thermal depolarization behavior of Bi1/2(Na0.8K0.2)1/2TiO3 ceramics are investigated. Fe doping at an appropriate level (≤ 3.0%) improves piezoelectric property and thermal stability simultaneously, due to the stabilization of long-range ferroelectric order. Piezoelectric constant d33 increases from 125 pC/N to 148 pC/N with Fe amount of 3.0%, and then decreases. The depolarization temperature Td is promoted continuously with Fe addition, from 76 °C for the undoped sample to 118 °C for the sample with Fe amount of 5.0%. It is proposed that the piezoelectric property and thermal stability can be simultaneously improved by stabilizing the long-range ferroelectric order in Bi1/2Na1/2TiO3-based systems with obvious relaxor character. This work provides a new insight into the improvement of Bi1/2Na1/2TiO3-based lead-free piezoelectric ceramics.