GLASS-FORMING ABILITY OF RARE-EARTHS IN FLUOROZIRCONATE GLASSES

The effects of rare earth elements on glass formation regions in the systems ZrF4-BaF2-LnF3-AlF3 (Ln is a rare earth element and AlF3 concentration is 4 mol%) has been examined. It is found that glass formation regions gradually shift to higher concentrations of rare earth fluoride with decreasing rare earth element radius. As a result of measurements of optical absorption, luminescent and electron-phonon spectra of Eu3+ ions as local probes of the glass structure in the system 55(mol%)ZrF4-35BaF2-5LnF3-4AlF3-1EuF3 (Ln = La, Eu, Gd, Th, Dy, Yb), it is determined that 5D0-7F2 and 7F0-5D2, supersensitive electronic transitions, intensities of Eu3+ ions decreased with decreasing rare earth elements radius. In total, the results obtained indicate that the increasing glass-forming ability of rare earth fluorides in La to Lu rank is explained by the increasing degree of Ln-F bond covalency.