FT-IR, FT-RAMAN AND MO-95 MAS-NMR STUDIES ON THE STRUCTURE OF IONICALLY CONDUCTING GLASSES IN THE SYSTEM AGI-AG2O-MOO3

Local environments of molybdenum in glasses of the system (AgI)(y)-[(A g2O)(x)-(MoO3)(1-x)](1-y) were investigated by use of near-infrared Fo urier transform (NIR-FT) Raman spectroscopy, FT-IR spectroscopy, and M o-95 magic-angle spinning (MAS) NMR. Specifically, the following cross -sections of the composition diagram were studied: series I: x = 0.5, and 0.50 less than or equal to y less than or equal to 0.75 and series II: y = 0.50, and 0.4 less than or equal to x less than or equal to 0 .5. Comparison of the spectroscopic results with those obtained on cry stalline model compounds indicates that the structures of series I-gla sses (composition ratio Ag2O/MoO3 = 1) are solely based on Ag+, I-, an d isolated MoO42- anions. On the other hand, glasses of series II (com position ratio Ag2O/MoO3 < 1) have a more complex structure consisting of both tetrahedral orthomolybdate, MoO42-, and a second, polynuclear species, in which MoO6 octahedra are linked to MoO4 tetrahedra in a m anner similar to the structure of crystalline Na2Mo2O7. (C) 1998 Elsev ier Science B.V. All rights reserved.