MOSSBAUER, FT-IR, AND XRD STUDY ON THE CRYSTALLIZATION OF HIGHLY FUNCTIONAL TUNGSTATE AND VANADATE GLASSES

Fe-57-Mossbauer spectra of 38Na(2)O . 61WO(3) .(Fe2O3)-Fe-57 glasses, heat treated at 355 degrees C for 5-150 min, show a change of the coordination number of Fe3+ from 6 (FeO6 octahedra) to 4 (FeO4 tetrahedra), as a result of the formation of Na2W2O7 (Na2O/WO3=1/2), Na2WO4 (Na2O/WO3=1.0), FeWO4, and Fe2WO6 phases. Fe-57-Mossbauer spectra of 25K(2)O . 65V(2)O(3) . 10Fe(2)O(3) glasses show a drastic decrease of Delta and Gamma after the heat treatment at 340 degrees C for 10-2100 min, since a homogeneous crystallization took place without a phase separation. A KV3O8 phase with the K2O/V2O5 ratio of 1/3 was precipitated, and the ratio was equal to the K2O/(V2O5+Fe2O3) ratio of the original 25K(2)O . 65V(2)O(3) . 10Fe(2)O(3), glass.