Composition dependence of the local structure and transparency of Gd<sub>2</sub>O<sub>3</sub>–B<sub>2</sub>O<sub>3</sub> binary glasses prepared via aerodynamic levitation

Gd2O3–B2O3 binary glasses with a wide composition range were fabricated using a levitation technique, which allowed the Gd2O3 content of the glasses to be increased to 60 mol %, which is much greater than possible using conventional melt-quenching techniques. The composition dependence of the thermal, optical, and vibrational properties of the Gd2O3–B2O3 binary glasses was investigated. The glass transition and crystallization temperatures decreased slightly in the B-rich region with increasing Gd2O3 content in the glasses, whereas they increased in the Gd-rich region. Both B- and Gd-rich glasses were found to be colorless and transparent over a wide range of visible to near-infrared radiation. With an increase in the Gd2O3 content, the optical absorption edge in the ultraviolet region shifted toward a longer wavelength. Additional infrared (IR) transmittance windows were observed in the Gd-rich region. Raman scattering and IR spectra revealed that in the Gd-rich glasses, all of the B atoms formed isolated BO3 units and the signals for the BO4 units disappeared. It was concluded that the characteristic local structure around the B atoms is the origin of the additional IR transparency. These results show that by adjusting the Gd2O3 content, the resultant borate glasses are expected to be applied as optical components for use over various wavelengths.