Formation and properties of the new Al8V10W16O85 and Fe8-x Al x V10W16O85 phases with the M-Nb2O5 structure

A new, previously unknown phase Al8V10W16O85 has been obtained from reaction taking place in the solid state. It forms continuous solid solution with Fe8V10W16O85 of the Fe8-x Al (x) V10W16O85 general formula. All these phases are isostructural with M-Nb2O5 and (W0.35V0.65)(2)O-5 and belong to a block structure phases with ReO3 type blocks of 4 x 4xa dimensions. Al8V10W16O85 is tetragonal and has the lattice constants a = b = 1.9487(1) nm and c = 0.36706(4) nm. It melts incongruently at 1,183 K depositing Al-2(WO4)(3) and WO3. The increase of the Al3+ ions content in the crystal lattice of Fe8V10W16O85 causes the melting point increasing, and decreasing of a = b unit cell parameters with c being almost constant. IR spectra of Al8V10W16O85 and Fe8-x Al (x) V10W16O85 phases have been recorded.