Thermal-stress enhanced pyroelectricity in piezoelectric bimorphs.

Abstract

Enhancing pyroelectric performance is essential for advancing thermal sensing and energy-harvesting applications. This study presents an effective strategy to achieve highly enhanced pyroelectricity in a flexible polyvinylidene fluoride/mica bimorph. Unlike conventional approaches that focus on domain-phase engineering to enhance intrinsic pyroelectric contribution, we engineer a more dominant role for the secondary pyroelectric contribution by a stress-induced shape change that couples to a change in the polarization via the piezoelectric effect. This mechanism is enabled by the favorable combination of a large thermal-expansion mismatch between the polymer (polyvinylidene fluoride) and the ceramic (mica), together with the inherent mechanical compliance of mica's flexibility, which allows interfacial thermal stresses to efficiently generate piezoelectricity. By combining experimental characterization with finite element modeling of the heterostructure's temperature-dependent curvature, interfacial thermal stress is identified as the dominant contributor to the large effects. Direct pyroelectric measurements reveal a highly enhanced pyroelectric coefficient ≈ -359 µC/m²K, more than an order of magnitude greater than that of single-layer polyvinylidene fluoride, highlighting its potential for applications in flexible electronics, thermal sensors, and energy harvesting systems.