Pressure-Volume-Temperature Behavior in the System H20-NaOH-Si02 And ItsRelationship to the Hydrothermal Growth of Quartz

Commercial hydrothermal growth of single-crystal a-quartz has been practiced for more than twenty years. It is arguably second only to Si * Western Electric, Merrimack Valley Works, No. Andover, Massachusetts 01845. 639 in its importance to electronics. The hydrothermal mineralizer or solvent used is either NaOH or Na 2 C0 3 and, particularly in the case of the more generally used NaOH, both the physical chemistry and crystal-growth aspects have been quite extensively studied, including phase relations,1 solubility,2 growth kinetics,3 distribution of impurities (especially OH),1 perfection, 5 and electrical properties 6 of grown quartz. However, the pressure-volume-temperature (p-V-T) relations for neither Na 2 C0 3 nor NaOH for mineralizer solutions saturated with quartz have been determined. Data on p-V-T for aqueous solutions of NaOH7"9 and Na 2 C0 3 7 are available, but their relationship to the silicasaturated solution used in growth is tenuous. For our purposes the system H 2 0--NaOH--Si0 2 is of particular interest since it is most used and probably most studied. We have directed our studies to it and have adopted it for production. 10 Indeed, except for recent p-V-T measurements in the system H 2 0--H 3 P0 4 --AIPO4, 11 under conditions of A1P04 saturation like those used for A1P04 growth, no p-V-T measurements of mineralizers saturated with the solutes used in hydrothermal crystal growth have been made. In the paper of Kolb et al.,11 we described a technique and equipment for rather rapid p-V-T measurements that can be easily applied to other saturated hydrothermal systems, and reviewed the literature summarizing p-V-T measurements in hydrothermal mineralizers.