Structural Chemistry of A(VOPO4)2·nH2O (A = Alkali, Alkaline‐Earth, and Transition Metals)

Crystals of layered phosphate hydrates A(VOP04)2·nH2O (A = metal cation) have been grown under bydrothermal conditions. All compounds except trihydrates Pb(VOP04)2·3H2O and Ni(VOP04)2·3H2O consist of layers of vanadium phosphorus oxide with metal cations and water molecules between the layers. The layer is a four‐connected net in which corner‐sharing vanadium oxygen polyhedra and phosphate tetrahedra alternate. Most phases crystallize in crystal symmetry lower than those prepared from redox intercalation reactions. Their crystal structures and the structural relationships with VOPO4·2H2O are discussed.