TRIRUTILE PHASES OF HTAWO6-CENTER-DOT-XH2O - VIBRATIONAL PROPERTIES AND ELECTRICAL-CONDUCTIVITY

The phases of HTaWO6 · xH2O (x = 3/2, 1/2, 0) system with trirutile structure, including fully anhydrous TaWO5.5, were characterized by X-ray and thermoanalytical methods and investigated by Raman scattering and complex impedence spectroscopy. The vibrational study involved the LiTaWO6 precursor as well. Raman spectra show an evolution correlated with progressive water loss after selective heat treatments, up to 900°C. In some conditions, a disordered modification of TaWO5.5 appears in the spectra even below 300°C. The ionic conductivity is smaller than in the pyrochlore polymorph and can be ascribed to a lower mobility of H+ ions in the trirutile structure, with an activation energy of 0.35 eV. © 1993 Academic Press, Inc.