Anisotropy optical properties of KSr₂Nb₅O₁₅ lead-free ferroelectrics: First-principle calculations

The electronic and optical properties of KSr₂Nb₅O₁₅ (KSN) are investigated via first principle calculations along (100), (010), and (001) directions. The results show that KSN has a huge anisotropy in optical properties with a larger dielectric constant, reflectivity, refractive index and extinction coefficient at (001) direction than that at (100) and (010) directions, suggesting much easier transition of electrons at (001) direction. Dielectric function and conductivity calculation results verify that electronic transition mainly appears between Nb-4d and O-2p state. KSN is transparent in the range of 0–2.3 eV, while shows refractivity in the range of 2.5–5 eV and shows favorable reflectivity in the range of 3.6–7.8 eV. These theoretical insights into the microscopic intrinsic properties of KSN would provide fundament for further understanding KSN materials and broadening its application fields.