Structural and optical characteristics of B2O3-TeO2-Bi2O3-SrCO3-K2CO3-Er2O3 glass systems: Role of Er3+doping

A series of Er3+-doped telluro-borate glasses with the chemical composition (70-x) B2O3-5TeO2-10Bi2O3- 10SrCO3-5K2CO3-xEr2O3 (where x = 0.5, 0.7, 0.9, 1.1, and 1.3 mol%) were synthesized using the traditional melt quenching technique. Their structural and optical properties were analyzed using XRD, FTIR, Raman, EDX, and UV-Vis-NIR measurements. The XRD shape proved the amorphous nature of the glasses, while EDX analysis revealed their elemental composition. The primary stretching vibrations of the different borate and tellurite networks were identified using FTIR and Raman spectroscopy. The bonding character was determined from the absorption spectra band positions by calculating the nephelauxetic ratio (beta) and bonding parameters (delta) to assess the ionic or covalent nature of the bonds. The direct optical band gap energy decreases from 3.214 to 3.173 eV, while the indirect band gap energy declines from 3.082 to 3.011 eV. Additionally, the Urbach energy (Delta E) decreases from 0.349 to 0.145 as the concentration of erbium increases. The high refractive index values and the range of the metallization criterion indicate that the B2O3-TeO2-Bi2O3-SrCO3-K2CO3-Er2O3 glasses are well-suited for optoelectronic and nonlinear optical devices.