Phase transformation in lead titanate based relaxor ferroelectrics with ultra-high strain

The reverse piezoelectric effect allows for the conversion of an electrical input signal into mechanical displacement and forms the basis for the operation of positioners and actuators. Addressing the practical need for cost-effective sensitive materials, we introduce erbium-doped lead magnesium niobium titanate ceramics which exhibit exceptionally high strain (3.19% bipolar and 0.8% unipolar) under a very low applied field of 2 kV mm^-1, resulting in record-breaking piezoelectric coefficients (d₃₃* values of 15,950 and 4014 pm V^-1, respectively). These exceptional properties stem from a combination of factors including the sensitivity of polar nanoregions to the applied field in this relaxor ferroelectric system, the thickness of the sample, and the energetic availability of polymorphs with different polar structures where a change in polarisation direction occurs at the field induced phase transition. Surpassing the performance of single crystal materials, our findings establish a benchmark in piezoelectric performance with implications for many diverse applications.