Synthesis of ultra-fine columbite powder MgNb2O6 by the polymerized complex method

Pure MgNb2O6 powders with high specific surface area and high crystallinity have been successfully synthesized by the "Polymerized Complex (PC) Method". A solution of water, citric acid, ethylene glycol and niobium and magnesium ions, was polymerized at 130 degrees C by the water elimination and was calcined at 400 degrees C for 2 h. The precursor formed was calcined at temperatures from 700 degrees C to 1000 degrees C in air to obtain the columbite phase. Thermal analysis, Raman spectroscopy, x-ray diffraction, adsorption/desorption hysteresis and scanning electron microscopy were used to investigate the polymer decomposition and the columbite phase evolution. No evidence for phase separation of crystalline MgCO3 and Nb2O5 in Raman spectra and x-ray diffraction pattern as distinct intermediates were found, and the MgNb2O6 probably is formed through a single-step decomposition of oxycarbonate intermediate, as other double oxide synthesized by the PC Method, as indicated by the thermal decomposition of the precursor.