Enhanced structural and physical properties of Sb2O3–K2O-B2O3 glasses: role of B2O3 incorporation

Abstract

A series of antimony-based glasses with the nominal composition (80-x)Sb2O3–20 K2O-xB2O3 (0 ⩽ x ⩽ 40 mol%) was synthesized using the conventional melt-quenching technique. X-ray diffraction indicates the amorphous nature of all prepared samples. The influence of B2O3 incorporation on the structural, thermal, physical, optical, and elastic properties was investigated. Increasing the B2O3 content leads to a systematic decrease in density (ρ) from 4.6765 to 3.7234 g cm−3 and molar volume (Vm) from 53.898 to 43.855 cm3 mol−1, indicating enhanced structural compactness and packing efficiency. This behavior is supported by reduced free volume (Vf) and oxygen molar volume (VO), along with increased oxygen packing density. Attenuated total reflection Fourier–Transform infrared spectroscopy and Raman spectroscopy suggest a gradual transformation of boron structural units from trigonal BO3 to tetrahedral BO4 configurations, thus signaling a transition from a less connected to a more polymerized three-dimensional glass network. The average Boron–Boron separation distance d〈B–B〉 further suggests this structural rearrangement. Differential scanning calorimetry demonstrates good thermal stability, with only slight variations in the glass transition temperature (Tg) between 262 and 274 °C. Optical investigations show an increase in the optical band gap energy (Eg) from 2.894 to 3.123 eV, accompanied by a decrease in Urbach energy (Eu) from 0.362 to 0.333 eV, reflecting reduced structural disorder and improved network homogeneity. Elastic properties evaluated theoretically using the Makishima–Mackenzie model and experimentally via ultrasonic measurements reveal a significant increase in elastic moduli (Young’s, bulk, shear, and longitudinal) and Debye temperature (from 114.004–152.649 K) with increasing B2O3 content, indicating enhanced rigidity and network connectivity. K2O glasses, making them promising candidates for optical, photonic, and nonlinear applications.