SiO2-Fe2O3-K2O系ガラスから生成したFe-leucite結晶の転移温度

The glasses of SiO2-Fe2O3-K2O system were heat-treated at 800°C-1100°C, and the inversion temperature and the lattice constants of Fe-leucite crystals precipitated in the glass were measured by using DTA apparatus and X-ray diffractometer.It was found that the change of inversion temperature was closely related with the atomic ratio δ=Si/(Si+Fe+K) of the mother glass composition. Each Fe-leucite crystal precipitated in the glasses with δ 0.5 lowered with the increase of δ. The lower crystallization temperature was, the more steep the degree of lowering was. It was also observed that there is a linear relationship between the inversion temperature and the lattice parameter c/a, when δ>0.5.It was considered that in the case of δ>0.5, Fe-leucite crystal having the composition of (KFe)1-xSi2+xO6(x>0) had a higher symmetrical lattice than the ideal one and the lattice defects which might be caused by the defficiencies of K+ increasing with δ.The influence of other phases such as residual glass, hexagonal KFeSiO4 crystals and hematite crystals on the inversion temperature was not observed.