LINBWO6 - CRYSTAL-STRUCTURE OF ITS 2-ALLOTROPIC FORMS

Two forms of LiNbWO//6 were previously described: a trirutile phase and another form claimed to be isostructural with LiNbO//3. The trirutile phase, called alpha -LiNbWO//6, transforms into the other form, beta -LiNbWO//6, at 820 degree C, which, in turn, decomposes at 870 degree C into NbW//2O//8 and Li//2WO//4. The structures of alpha and beta -LiNbWO//6 are solved from powder diffraction data analyzed by the Rietveld method. alpha -LiNbWO//6 adopts a new quasi-ordered trirutile structure, while beta -LiNbWO//6 exhibits the LiNbO//3 structural type, where Nb and W are completely disordered.