Sintering experiment in the system NaAlSiO₄-KAlSiO₄

Abstract

A cursory survey on subsolidus equilibria in the system NaAlSiO₄-KAlSiO₄ was made through sintering of mixtures of chemicals in the proper proportions. The phases were identified by means of the X-ray diffractometer. The results ane shown in Figs. 1 and 2, and Tables 1 and 2.
There exists a large miscibility gap between the fields of nepheline and kalsilite. Potassium-rich nepheline stablle at high temperatures should unmix under equilibrium conditions at lower temperatures, giving kalsilite together with more sodic nepheline, as shown in Fig. 3.
An unidentified phase “A” is formed at lower temperatures than the orthorhombic form in the region with higher K/Na ratios than kalsilite.
The unit cell dimensions of kalsilites were measured as shown in Table 2.