Intercalation Compounds of Vanadyl Phosphate Dihydrate with Rubidium Ion and Their Electrical Properties

Abstract

Intercalation compounds of vanadyl phosphate with rubidium (RbxVOPO4·yH2O) were prepared by reacting VOPO4 with rubidium iodide solutions in acetone/water (volume ratio 9:1) at temperatures between 18 and 40 °C. Two phases with interlayer distance of 0.703 and 0.644 nm were formed during the intercalation; their composition is 0.20 ≤ x ≤ 0.28 and x ≥ 0.48, respectively. The water content of the intercalates increases with decreasing the rubidium content and goes from y = 1.4 for x = 0.557 up to y = 2.2 for x = 0.110, at 58% relative humidity. Samples with x = 0.18, 0.28, and 0.48 were investigated by ac and dc conductivity measurements which were carried out on pellets at 20 °C as a function of relative humidity (RH). In all cases the conductivity is fully electronic up to 30% RH. The electronic conductivity of the 0.703 nm phase is ∼10-7 S cm-1 at 0% RH and reaches a maximum (∼10-5 S cm-1) at around 5% RH. No appreciable change is correspondingly observed in the electronic conductivity of Rb0.48VOPO4·yH2...