Stabilization of the ferrielectric phase in NaNbO3-based lead-free ceramics for a wide-temperature large electrocaloric effect

The environmentally friendly antiferroelectric NaNbO3 (NN) has attracted a great deal of attention in recent years due to its special structure and outstanding electrical properties; thus, many efforts have been made to modify its antiferroelectricity in order to achieve a repeatable double polarization-electric field (P-E) loop. In this work, the (1-x)NaNbO3-xCaZrO(3) (NN-xCZ) system was chosen as a case study in order to reveal the origin of the realization of reversible antiferroelectricity through compositional modification. Through the construction of a phase diagram based on multi-scale structural analysis, the newly discovered high-temperature ferrielectric (FEi) phase with the P2(1)ma space group moves to around room temperature after adding a secondary ABO(3) material, leading to the achievement of a repeatable triple P-E loop as well as a large electrocaloric effect in a wide temperature range. Owing to the gradual change in net polarization without a change in the modulation wave vector, the polymorphic phase transition from the antiferroelectric P phase to the new FEi phase on heating exhibits a weak dielectric anomaly with relaxor behavior in NN-based ceramics. The exploration of the mechanism of antiferroelectricity as well as its reversibility in NN-based lead-free ceramics would provide guidance for the design of high-performance materials with novel polarization configurations.

Automated summary

This study investigates the mechanism of achieving reversible antiferroelectricity through compositional modification. The results show that adding CaZrO3 into the NaNbO3 matrix can shift the high-temperature ferroelectric phase to around room temperature, leading to repeatable triple P-E loops and a large electrocaloric effect.