The unary phase diagram for SiO2 is
Locate the triple
point where solid, liquid, and vapor coexist and give the temperature and the type
of solid present. What do the other
“triple” points indicate?
The Correct Answer and Explanation is :
In the unary phase diagram of silicon dioxide (SiO₂), several key triple points exist where three distinct phases coexist in equilibrium. One significant triple point occurs at a temperature of approximately 1,470°C, where the solid phase β-cristobalite coexists with liquid and vapor phases. At this juncture, SiO₂ can simultaneously exist as a solid (β-cristobalite), a liquid, and a vapor.
Another notable triple point is found at approximately 1,713°C, where the solid phase β-tridymite coexists with liquid and vapor phases. This indicates that at this specific temperature, SiO₂ can exist simultaneously as β-tridymite, liquid, and vapor.
Additionally, the phase diagram features a triple point at approximately 573°C, where the solid phases α-quartz and β-quartz coexist with the vapor phase. This point signifies the equilibrium between these two polymorphs of quartz and vapor.
These triple points are critical in understanding the phase behavior of SiO₂ under varying temperature and pressure conditions. They delineate the precise conditions under which multiple phases can coexist, providing valuable insights into the thermodynamic properties and stability regions of different SiO₂ phases.
Understanding these triple points is essential for applications involving SiO₂, such as in materials science and geology, where precise control over phase transitions can influence the properties and functionalities of silica-based materials.