Structural and optical characterization of semiconducting Cr2O3-modified lithium borate glasses

Glasses with compositions (50−x)Li2O–xCr2O3–50B2O3 with varying Cr2O3 contents (0–20 mol. %, with an interval of 4 mol. %), were synthesized using the melt-quenching method, and their structural, thermal, physical, and optical properties were examined. In the XRD pattern, a broad hump appears, indicating the amorphous nature of the glass system. Elementary analysis is corroborated by electron diffraction spectra. Thermal investigations show that the glass transition temperature increases with rising Cr2O3 content, with the LCB3 composition exhibiting the highest thermal stability among all the samples. FTIR and Raman spectroscopic data show a systematic transformation of tetrahedral BO4 units into trigonal BO3 units, indicating that Cr2O3 functions as a network modifier. UV–Vis diffuse reflectance spectroscopy spectra exhibited three characteristic absorption bands at 380, 436, and 605 nm, which are attributed to 4A2g → 2A1g, 4A2g → 4T1g (F), and 4A2g → 4T2g electronic transitions, respectively. The optical bandgap decreases, and Urbach energy increases with an increase in the Cr2O3 content, reflecting enhanced structural disorder and formation of localized states within the band structure. In addition, several optical parameters, including the refractive index, dielectric constant, optical dielectric constant, molar refraction, metallization criterion, molar electronic polarizability, transmission loss, reflection loss, linear susceptibility, and third-order nonlinear susceptibility, were calculated. The observed variations in these parameters highlight the significant effect of the addition of Cr2O3 in the glass matrix. Overall, the results demonstrate that the introduction of Cr2O3 into lithium borate glasses exhibits pronounced modifications in the structural and optical characteristics, establishing the potential of these glasses for nonlinear optical and optoelectronic device applications.