Impact of Leakage for Electricity Generation by Pyroelectric Converter

Pyroelectric energy converters are functional capacitors that use a pyroelectric material as the dielectric layer. By utilizing a first-order phase transformation of the material, a pyroelectric device can generate an adequate amount of electricity from small temperature fluctuations. However, most pyroelectric capacitors leak during energy conversion. In this paper, we analyze the thermodynamics of pyroelectric energy conversion with consideration of electric leakage. Our thermodynamic model is verified by experiments using three phase-transforming ferroelectric materials with different pyroelectric properties and leakage behaviors. We demonstrate that the impact of leakage on electric generation is prominent, and sometimes may be confused with the actual power generation by pyroelectricity. We discover a material candidate, $(\mathrm{Ba},\mathrm{Ca})(\mathrm{Ti},\mathrm{Zr},\mathrm{Ce}){\mathrm{O}}_{3}$, that exhibits a large pyroelectric current and an extremely low leakage current. A pyroelectric converter made of this material generates a pyroelectric current density of $1.95\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{A}/{\mathrm{cm}}^{2}$ and a pyroelectric work density of $0.2\phantom{\rule{0.2em}{0ex}}\mathrm{J}/{\mathrm{cm}}^{3}$ even after 1389 thermodynamic-conversion cycles.