Preponderant influence of disordered P4bm phase on the piezoelectricity of critical compositions of Na0.5Bi0.5TiO3-based ferroelectrics

We investigated the phase boundaries of three Na0.5Bi0.5TiO3-(NBT) based piezoelectric systems NBT-BaTiO3 (NBT-BT), NBT-K0.5Bi0.5TiO3 (NBT-KBT) and NBT-SrTiO3 (NBT-ST), all exhibiting similar piezoelectric responses (d33�180pC/N). We found that, apart from a qualitative difference (NBT-KBT/NBT-BT exhibits R3c-P4mm interferroelectric instability and NBT-ST does not), the critical compositions of all the three systems exhibit onset of a disordered P4bm phase. Our study suggests that the preponderant effect of this distortion overrides the interferroelectric instability, limiting the piezoelectric response of NBT-BT/NBT-KBT like that in NBT-ST. © 2021 American Physical Society.