High and thermally stable piezoelectricity in relaxor-based ferroelectrics for mechanical energy harvesting

Abstract

The utilization of relaxor-based ferroelectrics with high piezoelectricity is considered to be an effective way to enhance the power generation capacity of piezoelectric energy harvesters (PEHs). However, the severe depolarization behavior in the high-temperature region is the main issue that hinders the application of relaxor-based ferroelectrics in high-temperature PEHs. Here, the goal of obtaining a high piezoelectric charge coefficient (d₃₃) together with excellent temperature stability in relaxor-based ferroelectrics is achieved through a lattice distortion design strategy combined with domain configuration matching. Based on this concept, a new relaxor-based ferroelectric xPb(Zn_1/3Nb_2/3)O₃–(1 − x)Pb(Hf_yTi_(1−y))O₃ (xPZN–(1 − x)PH_yT_(1−y)) is investigated and the corresponding high-temperature PEHs are fabricated. A high Curie temperature of 319 °C and a large d₃₃ of 540 pC N⁻¹ are achieved at the optimal composition (x/y = 0.075/0.49) simultaneously, which are superior to those of the existing commercial PZT-based piezoceramics. The enhanced lattice angle distortion (|β-90°|) with a hierarchical domain configuration balances the piezoelectricity and thermal stability in relaxor-based ferroelectrics. Furthermore, the newly developed PZN–PHT PEH exhibits a stable output current over a broad temperature range (25–275 °C) and satisfactory cycling reliability (up to 200 000 cycles without degradation) at 250 °C. These characteristics demonstrate that the PZN–PHT relaxor-based ferroelectric is a promising candidate for high-temperature PEH applications.