Thermal and spectroscopic characterization of gallium-tellurite glasses doped BaF2 and PbO

The paper studies an influence of Ga2O3, PbO and BaF2 on the thermal stability of tellurite glass and their properties: thermal expansion coefficient, transmittance and refractive index. Three series of gallium-tellurite glass were prepared: I - (100 − x)TeO2·xGa2O3 where x = 5, 10, 15 and 25 mol%, II - (85 − x)TeO2·15Ga2O3·xBaF2 where x = 1, 3, 6, 11 mol%, III - (90 − x)TeO2·10Ga2O3·xPbO where x = 0, 5, 10 mol%. It was confirmed that stable gallium-tellurite glass can be produced without applying super-cooling methods in the range 5-15 mol% Ga2O3. Ga2O3 acts only as a stabilizer of the TeO2 glassy network when its content not exceed 15 mol%. As shown this effect is connected with the change in crystallization ability of orthorhombic and tetragonal forms of TeO2. It was found that the latter is preferable when Ga2O3 content increases. The increase of the Ga2O3 content over 20 mol% induces its spontaneous crystallization. Admixture of BaF2 and PbO to the Te2O-Ga2O3 glass diminishes a tendency to the glass crystallization. Tellurite glasses with Ga2O3, PbO and BaF2 show good transmittance in the VIS, NIR and MIR up to 5.5 μm. BaF2 and PbO, unlike Ga2O3, decrease the thermal expansion coefficient of tellurite glass. The change in the refractive index due to the admixtures was presented.