Pressure-volume-temperature behavior in the system H2O-NaOH-SiO2 and its relationship to the hydrothermal growth of quartz

We have measured the pressure-volume-temperature relations in the high-pressure solutions used to grow electronic quartz and used this data to establish safe operating conditions for commercial production. High-temperature aqueous solution (hydrothermal) quartz growth, because of the importance of its product to electronics, must be ranked as one of the more important crystal-growth processes. We report here a convenient laboratory method for hydrothermal p-V-T measurements and give pressure data in 1.0-mol NaOH and in 1.0-mol NaOH saturated with quartz as a function of temperature up to 450° C and 30,000 psi. These results are compared with pressures measured on production-sized equipment. The results are used to establish the temperature at which the gas phase disappears under various conditions. The steels used for construction of high-pressure production autoclave equipment are brittle below a specific temperature, which increases slowly with service. Our p-V-T data can be used to assure that high pressures are avoided at temperatures where the autoclave is brittle. Finally, the depressions of pressure are used to glean information about the nature of the solute species present during growth, and can ultimately be of use in quartz rate and perfection studies.