Flexo-Pyroelectric Effect.

Developing sustainable energy technologies is among the foremost challenges of this century and spawns the emergence of materials for ambient energy harvesting, such as photovoltaics, triboelectrics, and pyroelectrics. The conversion of ambient thermal energy (temperature fluctuations) into electricity through pyroelectric materials offers a promising route toward sustainable energy technologies. However, there is a critical limitation: The conventional pyroelectric effect is inherently restricted to noncentrosymmetric crystals, but excludes the centrosymmetric materials, even though they exhibit otherwise favorable properties. This symmetry dependence severely constrains the development of pyroelectric energy technology. Here, we demonstrate that the pyroelectric effect, typically observed only in noncentrosymmetric materials, can be induced in centrosymmetric materials via the flexoelectric effect. By introducing strain gradients using an atomic force microscope, we generated a giant pyroelectric coefficient of up to 1.25 × 106 μC·m-2·K-1 in SrTiO3. This strain gradient-induced pyroelectric effect, termed as the flexo-pyroelectric effect, decouples pyroelectric functionality from intrinsic material polarity. Our findings exceed the long-standing symmetry limitation in pyroelectric energy technology by proving that centrosymmetric materials can also exhibit robust pyroelectricity through strain engineering. The flexo-pyroelectric effect redefines the understanding of pyroelectricity and unlocks the vast library of centrosymmetric materials for designing next-generation energy harvesters, advancing sustainable technology development.