EPR and Optical Studies on Binary Mixed Alkali-Alkaline Earth
Oxide Borate Glasses Doped with Cu²⁺ Ions¹

G. Srinivas, J. Siva Kumar, Md. Shareefuddin, M. N. Chary, and R. Sayanna

Department of Physics, Osmania University, Hyderabad, Telangana state, India

e-mail: srinu123@gmail.com

Received July 22, 2014

Abstract—Mixed alkali alkaline earth oxide borate glasses of the composition (25 – x)Li₂O–xK₂O–12.5BaO–
12.5MgO–49B₂O₃–1CuO (x = 0, 5, 10, 15 and 20 mol %) were prepared by the melt quenching technique. The
X-ray diffractograms of all the glass samples were recorded at room temperature. Peak free X-ray spectra
revealed the amorphous nature of all the prepared glasses. Modulated differential scanning calorimetry
(MDSC) was used to determine the glass-transition temperature (T_g). The probable mixed alkali effect was
investigated using experimental techniques like density, molar volume, MDSC, electron paramagnetic reso-
nance (EPR), and optical absorption studies. From the EPR spectra the spin-Hamiltonian parameters were eval-
uated. The spin-Hamiltonian parameter values indicated that the ground state of Cu²⁺ is orbital (²B_1g) and
the site symmetry around Cu²⁺ is tetragonally distorted octahedral. The variation of g_|| and A_|| as a function of
Li₂O content was found to be nonlinear. A broad optical absorption band was observed in all the glasses con-
taining Cu²⁺ ions corresponding to ²B_1g ²B_2g transition. From the optical absorption studies the values of the
optical band gap (E_opt) for indirect, direct transitions and Urbarch energy (E) have been evaluated. By co-relat-
ing the EPR and optical absorption data, bonding parameters ², ² and were evaluated.

Keywords: borate glasses, modulated differential scanning calorimetry, EPR and optical absorption

DOI: 10.1134/S1087659616020152

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