Pb-free semiconductor ferroelectrics: A theoretical study of Pd-substituted BA (Ti ₁₋ₓ Ceₓ) O₃ solid solutions

We use first-principles density-functional-theory calculations to investigate the ground state structures of Ba⁡(Ti ₁₋ₓ Ceₓ) O₃ solid solutions containing Pd. Previous studies have shown that the properties of BaTiO₃, a Pb-free ferroelectric 𝐴⁢𝐵⁢O₃ perovskite, can be tailored via 𝐵-site substitution. In the present study, we substitute Ce for Ti to increase the overall volume of the perovskite, to then accommodate an O-vacancy-stabilized Pd substitution. Using the LDA+𝑈 method, we predict that these proposed materials will display a decreased band gap compared to BaTiO₃ while maintaining polarization. These features, combined with their environmentally friendly characteristics make these materials promising candidates for use as semiconducting ferroelectrics in solar-energy conversion devices.