Improved solid acid electrolyte materials, methods of synthesizing such
materials, and electrochemical devices incorporating such materials are
provided. The stable electrolyte material comprises a solid acid capable
undergoing rotational disorder of oxyanion groups and capable of extended
operation at elevated temperatures, that is, solid acids having hydrogen
bonded anion groups; a superprotonic, trigonal, tetragonal, or cubic,
disordered phase; and capable of being operating at temperatures of
.about.100.degree. C. and higher.