Phase transitions of leucite and solid solutions of leucite, obtained by crystallization of glasses in the K2O-CaO-Al2O3-Si02 system, have been investigated by means of high temperature X-ray diffraction and DTA.
The unit cell dimensions of leucite (a=13.08 Å, c=13.75 Å) change continuously with temperature up to the transition between the tetragonal and the cubic form at approximately 625°C, where a discontinuous change is observed. Solid solutions of the low temperature form of leucite (a=13.12=13.15 Å, c=13.69=13.74 Å) showed the same transition behaviour. The discontinuous change, however. occurred at a lower temperature, in one case as low as 300°C. For two samples a temperature interval of approximately 100°C occurred within which low and high leucite co-existed.
Two samples yielded the cubic form of leucite at room temperature (a=13.43 Å). The linear thermal expansion ooeffi-cient of high leucite was determined to be (11.7=12.8) 10-6(C-1)(25-600°C).
KeywordsSolid Solution Phase Transition Temperature Temperature Form Transition Behaviour Linear Thermal Expansion
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