Achieving Giant Piezoelectricity and High Property Uniformity Simultaneously in a Relaxor Ferroelectric Crystal through Rare-Earth Element Doping

The low uniformity in properties of relaxor ferroelectric crystals is a long-standing issue in the ferroelectric community, which limits the available volume of the entire crystal boule. The aim of this study is to develop a relaxor ferroelectric crystal with improved property uniformity and excellent piezoelectricity. To this end, Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ is doped with Nd₂O₃ (Nd–PIN–PMN–PT) to improve the crystal performance. Along the crystal boule, the piezoelectric coefficient d₃₃ varies from 2800 to 3500 pC N⁻¹, and the dielectric constant ranges from 8400 to 9800, with variations of 25% and 16%, respectively. Such high property uniformity results in over 75% available volume of the crystal boule, compared to 30–50% for undoped crystals grown by Bridgman method. At the electric field of 1 kV cm⁻¹, the converse piezoelectric response is up to 4780 pm V⁻¹. In addition, its Curie temperature (T_C) and coercive field (E_C) are above 150 °C and 3 kV cm⁻¹, respectively. Compared with Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ crystal (d₃₃: 1500 pC N⁻¹, T_C: 135 °C, E_C: 2.3 kV cm⁻¹), the larger piezoelectricity, the higher T_C and E_C, and improved uniformity make Nd–PIN–PMN–PT crystals promising candidates for advanced piezoelectric applications.