Theoretical insight into optical properties of ZnGa2O4 transparent ceramic

The spinel-type ZnGa2O4 transparent ceramic with extremely wide infrared transmission range exhibited great potential applications in numerous fields. Based on the comparative study with MgAl2O4 and ZnAl2O4, the optical properties of ZnGa2O4 transparent ceramic in the entire wavelength range from ultraviolet to infrared were theoretically investigated by first-principles calculations. With the in-depth understanding of crystal, electronic, phonon structures and chemical bonding, the origin of the variations in the optical properties was clarified. Due to the inherent 3d10 electronic configuration in both Zn and Ga, the significant p-d hybridization between Zn/Ga 3d states and O 2p states resulted in a smaller band gap and a higher refractive index of ZnGa2O4. The weaker tetrahedral Zn-O bond led to ZnGa2O4 considerably broaden its infrared transmission range. The easily formed oxygen vacancy defect coupled with the intrinsic narrow band gap may provide opportunities for new functionalization of ZnGa2O4 transparent ceramic. The comprehensive insight also offers guidance for designing novel transparent ceramics with desired optical properties.

Automated summary

Based on first-principles calculations, the optical properties of the spinel-type ZnGa2O4 transparent ceramic were theoretically investigated. The p-d hybridization between Zn/Ga 3d states and O 2p states and the weaker Zn-O bond were found to contribute to a smaller band gap and a higher refractive index, as well as the broadened infrared transmission range of ZnGa2O4. The oxygen vacancy defect and narrow band gap offer opportunities for functionalization of ZnGa2O4 transparent ceramic and guide the design of novel transparent ceramics with desired optical properties.