High performance PIN– PHT ceramics through addition of CuF₂ and low-temperature sintering

In this work, CuF₂-doped 0.08 Pb(In_0.5Nb_0.5)O₃–0.92 Pb(Hf_0.47Ti_0.53)O₃ (PIN–PHT + CuF₂) ceramics were prepared via traditional solid-state route using lower temperature than conventional environment. Resultant materials were found to have high Curie temperature, high mechanical quality factor and excellent piezoelectric performance. The phase composition as well as piezoelectric, dielectric and ferroelectric properties of the samples were detailedly studied, and Rayleigh's law fitting method was used to explore the piezoelectric response mechanism. Results indicate that the addition of CuF₂ makes PIN–PHT lattice shrink, the phase composition of morphotropic phase boundary (MPB) is more symmetrical, that is, the content difference between rhombohedral and tetragonal phases decreases, and both intrinsic and extrinsic contributions of piezoelectric response are improved. For CuF₂ doping content of 0.75-at%, samples sintering at 1100 °C exhibited excellent overall performance, its dielectric and piezoelectric properties at room temperature and Curie temperature reach excellent values, i.e., d₃₃ = 488 pC/N, T_C = 348 °C, ε_r = 1630, tan(δ) = 0.14%, Q_m = 387, and k_p = 0.6. More importantly, after depolarization at 200 °C, d₃₃ still remained at 460 pC/N. The combined results show CuF₂-doped PIN–PHT ceramics can be prepared at lower temperatures as well as have lower losses and higher values of Q_m. These findings indicate that PIN–PHT + CuF₂ ceramics have greater ease of production and significantly improved application prospects, particularly as a result of their high temperature stability.