Optical and structural properties of the BiTa1−xNbxO4 (0≦x≦1) compounds

Polycrystalline samples of BiTa1−xNbxO4 (0≦x≦1) were synthesized by a solid state reaction and characterized by powder X-ray diffraction. Rietveld structure refinement revealed that the variation of x in BiTa1−xNbxO4 (0≦x≦1) could cause the change in crystal structure. The structure of BiTa1−xNbxO4 (x=0.0 and 0.5) is triclinic system with space group P1. However, the structure of x=0.2, 0.8 and 1.0 is orthorhombic system with space group Pnna. Ultraviolet–visible diffuse reflectance spectroscopy measurement revealed that the band gap of triclinic compounds is wider than that of orthorhombic compounds.