It was demonstrated that, at heterophase interfaces between WO3 and MeWO4 (Me = Ca, Sr, Ba), interpenetration of the components of WO3 and MeWO4 occurred spontaneously or in an electric field. It was demonstrated that the amount of WO3 transported onto the inner surface of MeWO4 was defined by the magnitude of the electric charges which passed through the system, but did not depend upon the I–U parameters of the experiment. It was established that the magnitude of the Faradaic efficiency of WO3 transport in an electric field at 900C was similar for all compounds of the type, MeWO4 (Me = Ca, Sr, Ba), and amounted to 0.42 for the galvanostatic regime of the process. X-ray diffraction, X-ray-fluorescence, XPS and electron microscopy were used to explore the compositions of regions adjacent to the WO3/MeWO4 interface. The data obtained confirmed the formation of a non-autonomous phase, MeW-s, and its crucial role in the mechanism of processes which occurred at the heterophase interface: WO3/MeWO4. The true nature of the interface may be described by: WO3|MeW-s/MeW-s|MeWO4, which reflected the penetration of MeW-s into both initial samples. It was shown that a weight loss under spontaneous conditions could be caused by congruent sublimation of the MeW-s phase; due to its low surface energy and relatively low sublimation energy.

Surface Diffusion, Migration, and Conjugated Processes at Heterophase Interfaces between WO3 and MeWO4 (Me = Ca, Sr, Ba). A.Y.Neiman, N.N.Pestereva, E.V.Tsipis: Russian Journal of Electrochemistry, 2007, 43[6], 672-81