Synthesis, formation and characterisation of FeNbO4 powders

A modified mixed oxide synthetic route has been developed for the synthesis of iron niobate, FeNbO4 (FN). A rapid vibro-milling technique was employed, with the formation of FeNbO4 phases investigated as a function of calcination temperature and dwell time by XRD and DTA. The particle size distribution of the calcined powder was determined by laser diffraction techniques, and the morphology, phase composition and crystal structure determined via SEM, TEM and EDX. It has been found that the unreacted Fe2O3 and FeNb2O6 phases tend to form together with FeNbO4, with the latter appearing in both monoclinic and orthorhombic phases, depending on calcination conditions. It is seen that optimisation of calcination conditions can lead to a 100% yield of FeNbO4 in an orthorhombic, alpha-PbO2-type phase. (C) 1999 Elsevier Science Limited. All rights reserved.