Synthesis, characterization and structure determination of a three-dimensional hydrated potassium zinc divanadate: K[Zn2.5V2O7(OH)2]⋠H2O

K[Zn2.5V2O7(OH)2]⋅H2O was obtained by hydrothermal synthesis at 170 °C from a gel with the molar composition 1 V2O5; 1 ZnCl2; 4 KOH; 228 H2O. The solid crystallizes in the orthorhombic system, with the space group Pnnm (58) and with the unit-cell parameters a=14.5493(12)Å, b=10.1685(9)Å, c=6.0668(5)Å. The structure was determined from the powder XRD pattern by an “ab initio” method using the EXPO software and refined with the GSAS Rietveld refinement software. The structure can be described as formed from an interrupted and lacunary oxohydroxo zinc layers bridged by divanadate into a three-dimensional framework. The potassium cations and the water molecules occupy the channels between the bridged layers. The thermal stability, studied with the use of TGA and XRD, shows that the compound remains crystalline during the dehydration which occurs between room temperature and 210 °C.