Investigation of purification and composition change, of niobium hydroxide during heating

Using the methods of chemical, differential-thermal, thermographic analyses with identification of intermediate products by X-ray phase method studied is composition change of niobium hydroxide, which is received by the extraction with cyclohexane from sulphate-fluoride solutions. It is shown that in the course of heating different samples of niobium hydroxide gas extraction finishes at the temperature 400-430 deg C. For the samples with lower fluorine content the transition into crystal state is observed at higher temperatupe. It is established, that niobium pentoxide purification by means of calcination from the impurities of fluorine, sulphur and carbon up to the contents not more than thousandth parts of per cent must be carried out at the temperatupe higher than 1000 deg C. Practically complete purification from impurities in non-isothermal heating regime is reached at 700-800 deg C