Characterization of Cr3+ doped mixed alkali ions effect in zinc borate glasses – Physical and spectroscopic investigations

• Various physical parameters are evaluated and non-linear behavior is observed.
• Mixed alkali effect is observed in all physical and structural studies.
• EPR and optical studies confirmed distorted octahedral site symmetry.
• From optical absorption edges, optical band gap energies and Urbach energies are evaluated.

The physical and structural properties of Cr3+ doped 19.9 ZnO + xLi2O + (30 − x) Na2O + 50B2O3 (5 ⩽ x ⩽ 25) (ZLNB) glasses have been studied. Powder X-ray diffraction patterns indicated the amorphous nature of the glass samples. The physical parameters of all the glasses were also evaluated with respect to the composition. They exhibit the non-linearity providing the evidence for mixed alkali ions effect. The infrared spectra of the glasses in the range 400–4000 cm−1 showed the presence of BO3 and BO4 local structures in all the glass systems. No boroxol ring formation was observed in the structure of these glasses. Optical absorption and electron paramagnetic resonance studies were carried out at room temperature. From the optical absorption data various optical parameters such as optical band gap, Urbach energy were evaluated. Crystal field and Racah parameters are evaluated from optical absorption spectra. The EPR spectra of Cr3+ doped ZLNB glasses exhibited resonance signals at g = 4.066 and g = 1.9779 characteristic of Cr3+ ions. The evaluated bonding parameters suggest the covalent nature.

In the present studies EPR spectra exhibits the two resonances at g = 4.066 and 1.9779. Accordingly the resonance at g = 4.066 is assigned to the isolated Cr3O ions. The resonance at g = 1.9779 to exchange coupled Cr3+–Cr3+ pairs primarily. The g-values obtained from EPR results of Cr3+ doped ZLNB glasses indicate the distorted octahedral site.Figure optionsDownload high-quality image (100 K)Download as PowerPoint slide