DC conductivity, optical properties and Judd-Ofelt evaluation of 20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag mixed ionic-electronic glasses

Abstract

20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag glass system was prepared by melt quenching, and its DC conductivity, optical and spectroscopic properties were investigated. Its amorphous nature was confirmed by x-ray diffraction analysis. Results showed that DC conductivity σdc initially increased at x < 7 mol% and then decreased to a minimum at x = 11 mol% Bi2O3. UV–vis–NIR absorption spectra indicated six transition bands centered at 1496, 979, 799, 653, 544, and 521 nm corresponding to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 4S3/2, and 2H11/2 Er3+ transitions, respectively. Analysis on optical absorption edge by Tauc's plot revealed maximum in direct Eoptd(3.609 eV) and indirect optical energy bandgap Eopti(3.259 eV) at x = 11 mol%. Judd–Ofelt intensity parameter Ω2was calculated from optical absorption data to describe the intensity of electron transitions within the 4 f shells of Er3+ ions in the glasses. A minimum Ω2 was obtained at x = 11 mol%. The minimum values of σdc and Ω2 at x = 11 mol% are related to the presence of high bridging oxygen in the mixed ionic-electronic region that influences the symmetry of surrounding Er3+ ions.