Borophoshpate glasses of the ZnO-B_2O_3-P_2O_5 system

摘要

Twenty-eight samples of the ZnO-B_2O_3-P_2O_5 system were prepared by cooling the melt from 1230degC in the compositional series containing 30, 40, 50 and 60 mol/100 of ZnO. A large glass-forming region was found at the phosphate side of the ternary system with homogeneous glasses containing up to 20-40 mol./100 of B_2O_3. For these glasses, the density, ρ, molar volume, V_M, thermal expansion coefficient, α, glass transformation temperature, T_g, and dilatation softening temperature, T_d, were determined. The values of V_M and α decrease with increasing B_2O_3 content, while T_g and T_d increase. The reason for the observed changes is the incorporation of trigonal BO_3 and tetrahedral BO_4 units into the chain-like structural network of phosphates increasing thus its dimensionality. Raman and infrared (IR) spectra confirm these structural changes.