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Can silicon dioxide melt at 20 °C?

Can silicon dioxide melt at 20 °C?
Madison Answered Jun 20 2021

Can SiOX2 melt at 20 °C?

I have searched the web for SiOX2 phase diagram, but it seems to me that almost all the graph I can find have the temperature axis where the minimum temperature is in the hundreds degrees Celsius.

Is it theoretically possible that with an high enough pressure I can melt SiOX2 in a temperature range like ?30 °C to 50 °C? Or is it something theoretically simply impossible?

Babbie Answered Jun 20 2021

Question: Can SiOX2 melt at 20 °C?

According to experimental and calculated data values, my answer is no. See the phase diagram of pure silica based on the experimental and calculated data given in Ref.1:

Phase Diagram of silica

Reference 1 states that:

An internally consistent data set on the thermodynamic properties of the silica polymorphs stable up to 15 GPa (α‐quartz, β‐quartz, tridymite, cristobalite, coesite, and stishovite) and the liquid phase is presented. The data set was produced through a computer‐based assessment of the properties in which the available thermochemical (calorimetric), physical (bulk modulus and thermal expansion), and solid‐state and melting transition data (including some newly determined data on the high‐pressure polymorphs cosite and stishovite) were considered. The data set can be used to calculate phase relations at pressures of 0.1 MPa to 15 GPa and temperatures of 300 to 3200 K. The calculated phase diagram using these data agrees quite well with the phase equilibrium determinations except for the high‐temperature part of the coesitestishovite boundary. The properties of the liquid phase obtained are also in good agreement with the available data.

Keep in mind that 0.1 MPa1 atm. According to the phase diagram, cristobalite form is in liquid form at temperature grater than 1750 K in pressure range of 0.1?0.7 MPa. The extrapolation of that boundary would show it would never cross 20 °C point on x-axis without going to negative pressure. Therefore, it is impossible to have any form of SiOX2 in reduced or high pressusituations at room temperature or below.

References:

  1. V. Swamy Surendra, K. Saxena, Bo Sundman, J. Zhang, “A thermodynamic assessment of silica phase diagram,” Journal of Geophysical Research 1994, 99(B6), 11787-11794 (https://doi.org/10.1029/93JB02968).
 
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