Enhanced functional reversibility in lead-free ferroelectric material over long cycle pyroelectric energy conversion
Chenbo Zhang, Zeyuan Zhu, Ka Hung Chan, Ruhao Huang, Xian Chen
Abstract
The ferroelectric material usually exhibits temperature-dependent spontaneous polarization, known as pyroelectricity, which can be used to directly convert thermal energy to electricity from ambient low-grade waste heat. When utilizing the structural phase transformations of the material, the conversion capability can be magnified, consequently the device performance can be strongly boosted by orders of magnitude. However, common ferroelectric oxides suffer mechanical fatigue and functional degradation over cyclic phase transformations, hindering widespread applications of the energy conversion device. In this paper, we investigate the mechanical and functional reversibility of the material by lattice tuning and grain coarsening. We discover the lead-free compound $\mathrm{Ba}({\mathrm{Ce}}_{0.005}{\mathrm{Zr}}_{0.005}){\mathrm{Ti}}_{0.99}{\mathrm{O}}_{3}\text{\ensuremath{-}}0.10({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{TiO}}_{3} ({\mathrm{BaCeZrTiO}}_{3}\text{\ensuremath{-}}0.10{\mathrm{BaCaTiO}}_{3})$ satisfying the compatibility condition among all present phases by its lattice parameters, making the phase transformations highly reversible. We demonstrated that the energy conversion device with equiaxial coarse grains exhibits exceptional fatigue resistance, with stable pyroelectric current output at $4\phantom{\rule{0.28em}{0ex}}\textmu{}\mathrm{A}/{\mathrm{cm}}^{2}$ over 3000 energy conversion cycles. Our work opens another way to fabricate high-performance materials that advances the pyroelectric energy conversion for practical applications in engineering.