Achieving high piezoelectric response and elevated Curie temperature in Sm-modified PMN–PH–PT ceramics: A full-matrix characterization

Pb-based ferroelectric ceramics face a fundamental trade-off between a high piezoelectric response (d₃₃) and a low Curie temperature (T_C). Here, we demonstrate that combining Sm doping with a high-T_C PbHfO₃ (PH)-based ternary matrix can effectively shift this balance. A series of 0.01Sm–0.2(Pb(Mg_1/3Nb_2/3)O₃) (PMN)–(0.8−x)PH–x(PbTiO₃) (PT) ceramics were designed and systematically characterized. A morphotropic phase boundary (MPB) was identified at x ≈ 0.435, where the optimized composition exhibits a high d₃₃ (≈ 830 pC/N) together with an elevated T_C (≈ 256 °C), a combination that lies above the typical d₃₃–T_C trend of Pb-based ferroelectric ceramics. In addition, the ceramic exhibits stable piezoelectric performance up to ~230 °C, indicating excellent thermal stability. A full-matrix electromechanical characterization was performed, yielding a self-consistent set of elastic and dielectric constants and piezoelectric coefficients. Compared with a commercial lead zirconate titanate (PZT)-610HD benchmark, the designed ceramic offers a comparable d₃₃ but a 70 °C higher depolarization temperature. Atomic-resolution transmission electron microscopy (TEM) reveals heterogeneous local polar configurations in the optimized composition, providing microscopic structural evidence consistent with its excellent piezoelectric performance. This comprehensive property set not only clarifies the intrinsic structure–property relations but also provides a reliable database for high-temperature piezoelectric device design.