Borophosphate glasses of the ZnO-B2O3-P2O5 system

Twenty-eight samples of the ZnO-B2O3-P2O5 system were prepared by cooling t he melt from 1230 degrees C in the compositional series containing 30, 40, 50 and 60 mol.% of ZnO. A large glass-forming region was found at the phosp hate side of the ternary system with homogeneous glasses containing up to 2 0-40 mol.% of B2O3. For these glasses, the density, rho, molar volume, V-M, thermal expansion coefficient, alpha, glass transformation temperature, T- g, and dilatation softening temperature, T-d, were determined. The values o f V-M and alpha decrease with increasing B2O3 content, while T-g and T-d in crease. The reason for the observed changes is the incorporation of trigona l BO3 and tetrahedral BO4 units into the chain-like structural network of p hosphates increasing thus its dimensionality. Raman and infrared (IR) spect ;a confirm these structural changes. (C) 2000 Elsevier Science B.V. All rig hts reserved.