Nonstoichiometry in the LiMo2O3(PO4)2 structure: The molybdenotungsten monophosphate Li0.5MoWO3(PO4)2

A new molybdenotungsten monophosphate, Li0.5MoWO3(PO4)2 has been synthesized that crystallizes in the space group P21/m with a = 7.735(1) Å, b = 12.655(1) Å, c = 8.324(1) Å, b = 105.97(1) °. The [MoWP2O11]∞ framework is isotypic with that previously observed for LiMo2O3(PO4)2, lithium being located in six-sided tunnels running along a with an octahedral coordination. This phase differs from LiMo2O3(PO4)2, by the absence of lithium in the tetrahedral sites, showing that a significant lithium nonstoichiometry is possible. The stability is discussed with respect to other lithium monophosphates LiMoWO2(PO4)2 and Li0.2Mo2O3(PO4)2 that have different original structures.