Glass Formation in the System GeO ₂ ‐Bi ₂ O ₃ ‐Tl ₂ O

The occurrence of glass in the three binary and one ternary oxide systems containing Ge, Bi, and Tl was studied by air‐ and water‐quenching melted samples. Bulk glass occurred widely in these systems and was obtained with as little as 10 mol% GeO 2 , combined with 68 mol% BiO 1.5 and 22 mol% TIO 0.5 . Some glass occurred in all compositions except those with the highest Bi 2 O 3 or TI 2 O contents. Glass specimens were studied by differential thermal analysis to yield glass transition and crystallization exotherm temperatures; the thermal expansion coefficients and densities were also measured. Diagrams are presented to show the variation of these properties as well as λ 0 , the wavelength for zero material dispersion, in the binary and ternary systems. Based on these data, it is demonstrated that ultralow‐loss optical waveguides can be constructed in the 3‐3.5‐μm regionb.