Study of Anti-glass Phases in Heavy Metal Oxide Tellurite Systems

Glass and anti-glass samples of Bi2O3-TeO2 and Bi2O3-Nb2O5-TeO2 were prepared by ice quenching and normal quenching, respectively. Bi2O3-TeO2 system forms glass only up to 3-mol% of Bi2O3 however the higher concentration of Bi2O3 leads to the formation of an anti-glass phase of Bi2Te4O11. An anti-glass is a solid material in which the cations (Te4+, Bi3+, Nb5+) have long-range order but are statistically distributed at their sites while the anion sites are partially vacant. The addition of Nb2O5 to the Bi2O3-TeO2 system enhances the glass forming ability to a considerable extent. Samples from the system: xBi(2)O(3)-kNb(2)O(3)-(100-2x)TeO2 grow micro-inclusions or spherulites of the size of several micron within the glass matrix on slow melt-cooling. The addition of small amount of B2O3 is detrimental for the formation of anti-glass inclusions and forms purely glassy phase upon splat quenching. To functionalize these materials for luminescent applications, Dy3+ ions have been doped into the Bi2O3-Nb2O3-TeO2 system.