Influence of tin concentration on the electronic structure and ferroelectric behavior of barium titanate: Experimental and first-principles insights

To meet the growing demand for energy, multimodal energy conversion systems, such as photoferroelectrics, are receiving increased attention. Among these, oxide perovskites like Sn substituted barium titanate exhibit enhanced piezoelectric coefficient and dielectric permittivity at room temperature compared to the parent composition. This study investigates whether these enhancements originate from intrinsic Sn incorporation or extrinsic contributions. Additionally, the impact of Sn on the electronic bandgap is examined, which is critical for multifunctional applications. A combined experimental and first-principles approach is employed to systematically analyze different Sn concentrations (0–12.5 mol. % Sn), focusing on B-site ordering in BaTiO3. The experimental analysis includes dielectric and ferroelectric measurements, diffuse reflectance spectroscopy, and photoconductivity measurements for bandgap estimations. Computational screening reveals that Sn ions repel each other and preferentially adopt second neighbor B-site positions along the Ti–O–Ti bond. While the bandgap shows minimal changes (meV range), spontaneous polarization and polarization hysteresis decrease significantly with increasing Sn content. The experimentally observed increase in piezoelectric response is thus attributed primarily to extrinsic effects on the meso- and macroscales from the domain structure and the coexistence of phases around 11 mol. % Sn, rather than to intrinsic incorporation of Sn into the perovskite lattice.