Abstract
Equimolar Nb2O5:Li2O co-doped BGO70 (Bi2O3:GeO2 = 30:70) glasses were prepared via melt-quench method. Their XRD pattern and nonlinear variation in thermo-physical parameters revealed structural rearrangement with increasing concentration of doped oxides and indicated ceramization of BGO glasses. Density rho varied by 6.813-6.674 +/- 0.001 g cm(-3); molar volume V (M) (20.35-18.79) cm(3) and oxygen molar volume (16.80-15.60) cm(3) decreased monotonically. The glass transition temperature T (g) was between 449 and 457 +/- 2 A degrees C. Onset of crystallization temperature T (x) was raised from 502 to 511 +/- 2 A degrees C. Their DTA scans exposed two crystalline phases in the temperature range 25-800 +/- 2 A degrees C. The values for T (p1) and T (p2) observed were in the ranges 548-567 +/- 2 and 671-720 +/- 2 A degrees C, respectively. Peak apex temperatures T (p1), T (p2) increased nonlinearly with increasing mol% of Li2O and Nb2O5 in the system. Thermal stability factor Delta T (x) = T (x) - T (g) indicated that all the glasses in the system are equally stable. The difference Delta T (p1) = T (p1) - T (g) resistance against crystallization had values 96-113 +/- 4 A degrees C. The thermal coefficient of linear expansion (TCE or alpha) for these glasses corroborated that their thermal shock resistance was increased.