Silica Phase Diagram. The solid solution boundaries of mullite changed with increasing temperature and joined at 1890c and a composition of 7715 wt alumina. A phase diagram shows the different phases primarily solid and liquid and how they change with temperature.
In diagrams of pressure temperature fields of stability of silica minerals stability fields are not shown for keatite melanophlogite opal or the low forms of tridymite and cristobalite because they have not been demonstrated. Al si diagram is a eutectic diagram where solid solubility at least of aluminium in silicon is negligible and maximum solubility of silicon in aluminium at eutectic temperature is 165. The surfactant water silica phase diagram is shown in fig.
It is a relatively simple binary diagram where there is very little solubility at room temperature for si in al and for al in si.
Binary peritectic systems figure 612. Heavy lines are boundary curve dashed lines are liquidus isotherms in degree centigrade and the two liquid region is outlined by the zone of dots. According to alumina silica phase diagram 21 mullite 2al 2 o 3 ásio 2 phase boundaries join at 1890c. Quartz is the stable phase of silica under the physical conditions that prevail over most of earths crust.