PROPERTIES OF GLASSES BELONGING TO THE LI2O-ZRO2SIO2 SYSTEM

The behaviour and some physical, chemical and thermal properties of Li 2O-SiO2 glasses with ZrO2 additions (in the form of ZrSiO4) of up to 1 3.00 mol% in the as-quenched state were investigated with the aid of x -ray diffraction (XRD), FT-IR spectroscopy, thermal expansion, microha rdness and density measurements as well as chemical durability measure ments. Transparent glasses prepared by the addition of ZrO2 up to abou t 11.00 mol% were obtained. For successive addition of ZrO2 and decrea sing Li2O/SiO2 ratio, the expansion coefficients revealed decreasing v alues from 12.60x10(-6) to 8.69x10(-6)degrees C-1. The glass transitio n and softening point temperatures of the glasses showed a reverse beh aviour. By increasing the ZrO2 content in the base glasses the hardnes s and density values increased. However, while hardness increases even with the decrease of the Li2O/SiO2 ratio the density showed a contrar y behaviour, i.e. it increased with the ZrO2 content but decreased whe n the Li2O/SiO2 ratio decreased, with the highest values of 6.73 GPa a nd 2.71 g/cm(3), respectively. On the other hand, the chemical durabil ity, in the case of 30Li(2)O.70SiO(2) base glass, decreased with time in water solution and increased with ZrO2 content tending to be almost constant for ZrO2 contents higher than 4.76 mol% at 60 min and 6.98 m ol% in the time range from 5 to 30 min, respectively.