Synthesis and conductivity of substituted heteropoly acid with Dawson structure H7[Ga（H2O）P2W17061] · 18H2O

A new solid high-proton conductor, H7[Ga（H2O）P2W17O61]·18H2O, a substituted heteropoly acid with Dawson structure, has been synthesized by the degradation/ion-exchange/freezing method. The product was characterized by potentiometric titration, chemical analysis, IR, UV, XRD and TG-DTA. Complex impedance measurements show a high conductivity （5.44×10^-3 S/cm at 50℃）, with an activation energy for proton conduction of 36.04 kJ/mol. The mechanism of proton conduction is the Vehicle mechanism.