Density, Electrical and Optical Properties of Yttrium-Containing Tellurium Bismuth Borate Glasses
Abstract60B2O3-30Bi2O3-(10 − x) TeO2-xY2O3 mol.% (x = 0, 0.1, 1, 2 and 5) glasses have been prepared by the conventional glass-melting technique. The influence of Y2O3 on the density, optical and electrical properties of the glass was investigated. The density decreased whereas the molar volume increased with increasing Y2O3. Optical transmission in the ultraviolet (UV) spectral region indicated that the values of direct and indirect optical band gap energies increased, which was attributed to structural changes induced by the addition of Y2O3. Urbach energy values decreased with increasing the Y2O3, which was attributed to a decrease in the broadening due to static disorder-related parts. Fourier transform infrared (FTIR) spectra revealed that the addition of Y2O3 transforms BO4 to BO3 and BiO3 to BiO6 groups. The decrease in the dc and ac electrical conductivities was attributed to the formation of [BiO6] units which leads to a decrease in acceptor levels of Bi5+ sites. The electric modulus formalism indicated that the conductivity relaxation at different frequencies was a temperature-independent dynamic process. The full width at half-maximum (FWHM) of the normalized modulus decreases with increasing Y2O3 content, suggesting that the decrease of the Y ion–ion distance increases the interaction between the Y ions.