Abstract
The reaction sequences in the system, Na2O-Al2O3-2SiO2, have been investigated with various starting materials, and two different processes have been established. One is of the normal type, to low- or high-nepheline below 1250°C and to high carnegieite above 1250°C, and the other, to low-nepheline via high-carnegieite-like phase. In the latter sequence, variation of the temperatures of formation and transformation of the low-temperature phases is observed as due to the difference in the starting materials.
The difference in the reaction series is interpreted in terms of a structural inheritance of the product phase from the starting material.
The anion framework is almost maintained during the reaction, through which the diffusion and the rearrangement of cations take place to form a new phase. Based on this aspect, the reaction series, kaolinite→high-carnegieitelike phase→low-nepheline, is considered.
