The role of Bi2O3 and Sm2O3 on the thermal properties of phospho-zinc tellurite glasses

The present work reports role of Bi2O3 and Sm2O3 on the thermal properties of phospho-zinc tellurite glasses with composition 47.5 P2O5 - 45ZnO (5-x) Bi2O3 - 2.5TeO(2-x) Sm2O3 (where x=0, 0.3, 0.5 and 1 mol%) coded as PZBTS glass series system. Thermodynamic parameters such as Gibb's free energy (GFE) Delta G, entropy Delta S, etc., have been reported. This paper presents a comprehensive analysis of glass-forming tendency (GFT) and thermodynamic properties within the PZBTS glass system, elucidating key factors that influence glass stability and formation. The glass-forming tendency (K-T) is a pivotal parameter, showing that higher K-T values are associated with enhanced glass stability, while lower values indicate a propensity for devitrification, particularly accentuated with the addition of Bi2O3. Significantly, the mol% of Sm2O3 exerts a diminishing effect on K-T, emphasizing the interplay between rare earth elements and glass formation. Specific heat capacity (Delta Cp) is identified as an essential indicator, as its superiority to crystalline materials underscores favorable glass formation. Bond enthalpy (H) emerges as an effective gauge for estimating chemical bond strength in the glass network, reliant on the composition of Bi2O3 and Sm2O3. Meanwhile, the entropy of heat (Delta S) offers insight into disorder variation, a critical facet for successful glass formation. The ratio Delta G/Delta H becomes a crucial metric for assessing glass-forming ability, with values close to 0.2 signifying favorable characteristics. Moreover, molar density and volume exhibit an upward trajectory with increasing Sm2O3 mol%, leading to higher density and reduced molar volume due to the influx of rare earth ions. The density of rare earth ions (N) is calculated based on molar density and Avogadro's number, shedding light on ion distribution within the glass structure. Polaron radius (r(p)) provides valuable insights into structural features, while oxygen packing density (OPD) elucidates the intricate nature of the glass network. These findings collectively contribute to a deeper understanding of the thermodynamic and physical properties of the studied glasses, elucidating their glass-forming abilities and showcasing their potential applications in the realm of opto-electronic devices.