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

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 high piezoelectric charge coefficient (d33) together with excellent temperature stability in relaxor-based ferroelectrics is achieved through a lattice distortion design strategy combining domain configuration matching. Based on this concept, a new relaxor-based ferroelectric xPb(Zn1/3Nb2/3)O3-(1-x)Pb(HfyTi(1-y))O3 (xPZN-(1-x)PHyT(1-y)) is investigated and the corresponding high-temperature PEHs are fabricated. A high Curie temperature of 319 oC and a large d33 of 540 pC/N are achieved in the optimal composition (x/y = 0.075/0.49) simultaneously, which are superior to the existed commercial PZT-based piezoceramics. The enhanced lattice angle distortion (|β-90o|) with 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 oC) and satisfactory cycling reliability (up to 200000 cycles without degradation) at 250 oC. These characteristics demonstrate that the PZN-PHT relaxor-based ferroelectric is a promising candidate for high-temperature PEH applications.