Optical and structural properties of the BiTa1-xNbxO4 (0 <= x <= 1) compounds

Polycrystalline samples of BiTa1-xNbxO4 (0 less than or equal to x less than or equal to 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 less than or equal to x less than or equal to 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 Pl. However, th, 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. (C) 2001 Elsevier Science Ltd. All rights reserved.