Effects of melting temperature on color-changing in germano-tellurite niobate glass

Germano-tellurite niobate glasses have gained significant interest because of their applications in lasers and optical devices. However, germano-tellurite niobate glasses tend to turn brown or dark, which is a major disadvantage for visible optical systems. This work is devoted to exploring the mechanism of this color-changing. Glasses with a molar composition of 70TeO 2 -10GeO 2 -10K 2 O-10Nb 2 O 5 (TGKN) were synthesized by conventional melt-quenching at various melting temperatures. Different melting temperature leads the glasses to present different colors. The precise glass composition was revealed by ICP-OES, and the thermal properties, optical properties, and microstructure of the TGKN glasses were investigated. The XRD patterns and DSC curves suggest that the formation of Te metal is not the principal reason for the color-changing. A novel interpretation that the generation of T-Nb 2 O 5 causes the color-changing was proposed based on the transmittance, XPS and Raman spectra. This work will provide a new perspective on clarifying the effects of melting temperature on color-changing in the germano-tellurite niobate glass.