EPR, optical and physical properties of chromium ions in CdO–SrO–B2O3–SiO2 (CdSBSi) glasses

Chromium ions doped 10CdO–(20−x) SrO–50B2O3–20SiO2 (x = 0.5, 1.0, 1.5, 2.0, 2.5 mol%) (CdSBSi) glasses have been studied by using Electron Paramagnetic Resonance (EPR) and optical absorption techniques at room temperature. Powder XRD pattern of all the samples confirms amorphous nature of the glass. The low field spectral line of the EPR spectrum of chromium ions in CdSBSi glass is attributed to isolated Cr3+ ions and the high field spectral line is assigned for exchange of coupled pairs Cr3+ ions in all these glasses. The optical absorption spectra of Cr3+ ions in these glasses shows single broad band characteristic of Cr3+ ions in near octahedral symmetry. From this optical absorption spectral data the crystal field parameter (Dq) is evaluated from ultraviolet absorption edges, the optical band gap and Urbach energies are evaluated. The results assert that the optical band gap energy values are depended quite sensitively on added chromium content. The FT-IR spectral investigations of chromium ion doped glasses exhibits characteristic vibrations of BO3 units. Several physical parameters are also evaluated for these glasses with respect to the composition.

► Powder XRD patterns reveals the amorphous nature of the present glass matrix. ► EPR spectra exhibits two resonance signals near the low and high magnetic fields. ► From the EPR spectra g values indicate the distorted octahedral site. ► Optical absorption exhibits single band characteristic of Cr3+ ions in an octahedral symmetry. ► From band gap and Urbach energies, band gap energies decrease and Urbach energies increase.