Structure modulation, band structure, density of states and luminescent properties of columbite-type ZnNb2O6

Abstract

Zinc niobate ZnNb₂O₆, with a columbite-type structure, is a promising dielectric, photocatalytic and luminescent material, but the crystal structure has not been studied in detail. For the first time, we re-determined the crystal structure using single crystal X-ray diffraction and established the commensurately modulated structure model through high-dimensional formalism. The structure features a (3 + 1)-dimensional superspace group Pbcn(α00)00s with the modulation vector q = 1/3a*. At the same time, calculations of the band structure and the density of states were performed using density functional theory to reveal the electronic origins of the optical transitions. In addition, the photoluminescent properties of ZnNb₂O₆ were studied, showing that a broad emission band at approximately 470 nm can achieve a high quantum efficiency of up to 64% with an optimal sintered temperature of 950 °C.