Influence of processing conditions on crystal structure of BiNbO4 ceramics

Abstract Bismuth niobate (BiNbO 4 ) has attracted attention as a low-fired ceramics with promising microwave application potential. It belongs to the bismutocolumbite oxides with similarly to scheelite-like stibiotantalite structure (SbTaO 4 ) A 3+ B 5+ O 4 . The aim of the present research was to fabricate BiNbO 4 ceramics by solid state reaction route from the mixture of simple oxides viz. Bi 2 O 3 , and Nb 2 O 5 , and study its phase composition as well as crystal structure by X-ray diffraction method. The Rietveld refinement method was utilized for analysis of diffraction patterns. It was found that the mass change effects finished at temperature T =500°C and the total mass change was about Δ m =-0.78%. It was found that BiNbO 4 ceramics sintered in ambient air exhibited multiphase composition, i.e., apart from the major α -BiNbO 4 phase, the orthorhombic Bi 5 Nb 3 O 15 , Bi 3 Nb 17 O 47 and cubic Bi 3 NbO 7 phases were present. An increase in sintering temperature caused an increase in the amount of major α -BiNbO 4 phase which adopted an orthorhombic symmetry described well by Pnna (52) space group.