Production and properties of high purity TeO2− WO3−(La2O3, Bi2O3) and TeO2− ZnO−Na2O−Bi2O3 glasses

TeO2–WO3 (TW), TeO2–WO3–La2O3 (TWL), TeO2–WO3–La2O3–Bi2O3 (TWLB) and TeO2–ZnO–Na2O–Bi2O3 (TZNB) glasses were produced by high-purity oxide mixtures melting in platinum or gold crucible at 800 °C in the atmosphere of purified oxygen. The total content of Cu, Mn, Fe, Co and Ni impurities was not more than 0.1–0.5 ppm wt in the initial oxides and glasses. The stability of TZNB glasses to crystallization, characterized by (Tx − Tg) value more than 150 °C, was demonstrated by DSC measurements at heating rate 10 K/min. In the case of La2O3-containing glasses the thermal effects of both crystallization and fusion of the crystallized phases were not observed. The hydroxyl groups absorption coefficients of pure tellurite glasses at the maximum of the absorption band (λ ~ 3 μm) were in the region of 0.012–0.001 cm−1. The optical absorption losses, measured by the laser calorimetry method at λ = 1.56 and 1.97 μm, did not exceed 100 dB/km.