Glass formation and devitrification in the K2O–ZrO2–SiO2 system
Phys. Chem. Glasses, 2002, 43C, 462–5
A glass formation and devitrification study on the K2O– ZrO2–SiO2 system was performed by combining x-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Because of the high refractoriness of both ZrO2 and SiO2, and the volatility of K2O at high temperatures, homogeneous glassy samples resulted in being difficult to prepare. For all the examined samples, inductive coupled plasma (ICP) revealed that actual compositions were rather different from the tailored ones. A deeper characterisation was carried out on three compositions which are stable in the glassy phase (low reactivity with the atmosphere): K50Z20S30, K40Z30S30 and K40Z20S40. By applying thermal treatments on the samples to study the crystallisation behaviour, the devitrification of K50Z20S30 led to an unknown phase, while in case of K40Z30S30 a K2O.ZrO2.SiO2 phase already reported in literature could be recognised. A more complex devitrification process involves K40Z20S40 which finally produced khibinskite (K2O.ZrO2.2SiO2) by passing through the formation of β-K2O.SiO2.