Miscibility gap in the PbO-B2O3 system. Data according to different authors as indicated. Binodal temperatures (solid line) were fitted using the modified regular solution model of Simmons, 15 the critical temperature (1058 K 11 ), and the equilibrium compositions B2O3 and PbO·4B2O3. Reduced mixing entropy (ΔS/R = 7.2 ± 0.3) was adjusted to obtain the best line through the data. The liquidus temperature T liq = 1015 K (dashed-dotted line) was redrawn from Geller and Bunting. 10 The dashed lines illustrate the best straight lines through the data of the transition temperature T g of the B2O3-rich and PbO-rich glasses.
Absorption in the near infrared region of demixed PB1 and PB2 glasses.
Secondary electron images of relict structures of demixed drops in lead borate glass matrix. Distribution of drop ovality δ (a) in uncompressed glass PB2 after dwelling at 723 for 2 h (c). Distribution of drop ovality δ (b) in compressed (σ ax = 0.131 MPa) glass PB2 after dwelling at 769 K and cooling under load (d).
Size distribution of drops of the demixed glass PB1 after heat treatment at 773 K for 4 h. Mean radius is determined from fitting a Gaussian function through the data. (Inset) Mean radius cubed 3 vs. coarsening time t. Straight line displays best fit through the data.
Viscosity as a function of temperature of demixed glass PB2 and homogeneous glass PB3. Viscosity temperature curve of pure boron trioxide glass from Dietzel and Brückner. 48
Diffusivity vs. viscosity in the PbO-B2O3 glass system using double logarithmic scales. Data: D K = Diffusivity of the coarsening process (Eq. (10) ) and viscosity of matrix glass (Fig. 5 ) in demixed PB1 glass ( = 82.2 mol. %); 18O self-diffusivity 58 and viscosity 16 in boron trioxide glass ( ≈ 100 mol. %); 18O self-diffusivity 57 and viscosity 59 in PbO-rich lead borate glass ( = 31 mol. %); 207Pb self-diffusivity 56 and viscosity 59 in lead diborate glass ( = 66.7 mol. %). Eyring diffusivity calculated using Eqs. (7) and (8) for (1 + Cn) = 1.004, 2, 10, and 100 species per activated complex and (V M /(mN A ))1/3 = 240 pm. Upper x-coordinate scales diffusivity with the relative temperature T/T g of the matrix glass of the demixed PB1 and PB2 glasses (T g = 706 K).
Density ρ, composition of the initial supersaturated glasses PB1, PB2, and the homogeneous glass PB3, drop fraction ϕ, B2O3 content of drop and matrix in phase separated glasses PB1 and PB2 after dwelling at temperatures in the range from 723 to 773 K load-free (coarsening regimes) and under load (compression experiments under axial compressive stress σ ax), effective strain rate , drop ovality δ and liquid-liquid interfacial energy σ ll . Number in parenthesis gives uncertainty of the last digit.
Diffusivity in PbO-B2O3 glasses at 773 and 723 K. Data: Coarsening (Eq. (10) ) in demixed PB1 glass ( = 82.2 mol. %); 18O self-diffusivity in boron trioxide glass ( = 100 mol. %); 58 18O self-diffusivity PbO-rich lead borate glass (c 0 B2O3 = 31 mol. %); 57 207Pb self-diffusivity in lead diborate glass ( = 66.7 mol. %). 56 Eyring diffusivity of matrix glass in demixed PB1 and PB2 glasses was calculated using Eqs. (7) and (8) with CN = 1 and (V M /(mN A ))1/3 = 240 pm. Number in parenthesis gives uncertainty of the last digit.
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