Thermal and corrosion behavior of P 2O 5-Na 2O-CuO glasses

Abstract

Lead free sodium-copper-phosphate glasses in the range (mol%) 30-80P 2O 5, 0-70Na 2O and 0-70CuO were investigated. The glass formation region is P 2O 5≥40, CuO≤50 and Na 2O≤60 mol%. Glasses with a glass transition temperature ( T g) below 420°C, a thermal expansion coefficient from 258 × 10 −7 to 99 × 10 −7/°C and a dissolution rate in 30°C deionized water at the order of 10 −7 g/cm 2 min can be prepared. Substitution of CuO for Na 2O increases T g, the softening temperature ( T d), hardness and chemical durability and decreases the thermal expansion coefficient. The structure of 50P 2O 5-(50 - x)Na 2O- xCuO glass was examined by XPS and FTIR spectroscopies, which reveal the formation of POCu bonds in these glasses. The formation of POCu bonds, which replace PωO − ⋯ Na + bonds while keeping the same fraction of POP bonds, increases the crosslink density in the glass network and, therefore, enhances the chemical durability and increases T g, T d and the hardness of the glasses.