Stabilization of Ferroelectric Order in Bi1/2(Na0.8K0.2)1/2TiO3 Lead-Free Ceramics with Fe Doping

Abstract

The stabilization of ferroelectric order by Fe doping in Bi1/2(Na0.8K0.2)1/2TiO3 lead-free ceramics is reported. By introducing Fe3+, the ratio P r/P max shows a continuous increase, from 73.6% for the undoped sample to 80.8% for the sample doped with 3.0 mol.% Fe. The temperature corresponding to the pinching of polarization–electric field hysteresis loops is shifted toward higher temperature. The determined ferroelectric-to-relaxor transition temperature T F–R increases from 79°C to 111°C with Fe amount of 3.0 mol.%. Moreover, electron paramagnetic resonance spectroscopic analysis suggests the formation of $$ \left( {{\hbox{Fe}}_{\rm{Ti}}^{\prime} - V_{\rm{O}}^{ \cdot \cdot } } \right)^{ \cdot } $$ defect dipoles. The stabilization effect is thought to be related to the interaction between the defect dipole polarization and the spontaneous polarization. These results imply that Fe doping is an effective method to enhance the ferroelectric stability of Bi1/2Na1/2TiO3-based ceramics, which could be inspiring in developing novel lead-free materials with superior piezoelectric performance.