New Synthesis Routes for Indium-Doped Tin Pyrophosphate Proton Conductors

We have synthesized various indium-tin pyrophosphates using the traditional high-temperature method described in the literature as well as a novel solution-precipitation process developed in our laboratory. An ammonium-based precursor was used in an attempt to achieve a lower crystallization temperature. The use of this precursor in the solution-precipitation of indium-tin pyrophosphate gels resulted in precursors that could be crystallized at less than 600{degree sign}C. Inelastic neutron scattering studies indicate the presence of phosphate rich grain boundary phases that may be responsible for the high conductivity of the materials.