Fabrication, physical, thermal and optical properties of oxyfluoride glasses doped with rare earth oxides

The impact of the addition of different rare earth oxides such as Ho₂O₃, Nd₂O₃, Sm₂O₃, and Yb₂O₃ on the physical, structural, thermal, and optical properties of the prepared NaO₂–CaF₂ bismuth borate glasses was examined. FTIR spectra of the glass samples were performed in the range of 400–4000 cm⁻¹. UV–visible–NIR absorption spectral measurements were carried out of the range 200–2500 nm. Differential thermal analysis and the thermal expansion data of the prepared glasses were measured. FTIR the spectra of the proposed glasses showed that the rare earth mainly led to formation of BiO₆ and BO₄ groups as the intensity of peaks related to them increase with the addition of rare earth. An increase in the density of the glasses was noticed with the substitution of Na₂O by rare earth oxide. Addition of mol% Yb₂O₃ to glasses leads to increase in the ionic concentration, polaron radius and interionic distance of glasses and decrease the field strength and density. The obtained metallization values fluctuated between 0.3153 and 0.3570. The molar polarizability (α_m) and molar electronic polarizability (α_me) were enhanced with the increase of Yb₂O₃ content. The values of dielectric constants (ε and ε_opt) were decreased with in Sm₂O₃ and Nd₂O₃ glasses, whereas they increased in Ho₂O₃ glass. The T_s values were increased with the increase of rare earth oxide and Yb₂O₃ content. The optical energy gap decreases with the addition of rare earth oxide and Yb₂O₃ concentration. The refractive indices of all studied glasses are relatively high, thus one can concluded that the present glasses can be used as a candidate for optoelectronic, photoelectronic, and communications instruments and non-linear optical devices. The addition of Yb ions leads to decrease the emission and excitation intensity which may be attributed to concentration quenching effect.