Ferroelectric, pyroelectric, and piezoelectric properties of a photovoltaic perovskite oxide

A perovskite solid-solution, (1-x)KNbO₃-xBaNi_1/2Nb_1/2O_3-δ (KBNNO), has been found to exhibit tunable bandgaps in the visible light energy range, making it suitable for light absorption and conversion applications, e.g., solar energy harvesting and light sensing. Such a common ABO₃–type perovskite structure, most widely used for ferroelectrics and piezoelectrics, enables the same solid-solution material to be used for the simultaneous harvesting or sensing of solar, kinetic, and thermal energies. In this letter, the ferroelectric, pyroelectric, and piezoelectric properties of KBNNO with x = 0.1 have been reported above room temperature. The investigation has also identified the optimal bandgap for visible light absorption. The stoichiometric composition and also a composition with potassium deficiency have been investigated, where the latter has shown more balanced properties. As a result, a remanent polarization of 3.4 μC/cm², a pyroelectric coefficient of 26 μC/m² K, piezoelectric coefficients d₃₃ ≈ 23 pC/N and g₃₃ ≈ 4.1 × 10⁻³ Vm/N, and a direct bandgap of 1.48 eV have been measured for the KBNNO ceramics. These results are considered to be a significant improvement compared to those of other compositions (e.g., ZnO and AlN), which could be used for the same applications. The results pave the way for the development of hybrid energy harvesters/sensors, which can convert multiple energy sources into electrical energy simultaneously in the same material.