Improvements in or relating to methods of growing quartz crystals

摘要

Quartz crystals are grown on seed crystals suspended in a vessel capable of withstanding high temperatures and pressures, containing a mass of particles of quartzite, a sample of which shows no blackening in the grains of quartz when irradiated with X-rays, and aqueous medium containing sodium carbonate in a concentration of 0.5 to 3.0 N, the aqueous medium partially filling the vessel so that the ratio of the volume available to it after insertion of the quartzite to the volume filled by it is between 1.18 and 1.46, the vessel being sealed and heated so that the temperature of the aqueous medium is between 320 DEG and 400 DEG C., the solution in the region of the quartzite being at a temperature 5 DEG to 20 DEG C. higher than the solution in the region of the seed crystals, the mass and surface area of the quartzite initially being such that an average daily increase in thickness perpendicular to and on each of the growing faces of the seed crystals is between 0.3 and 1.0 mms. The sample of quartzite is tested as described in Specification 811,213. The vessel, which is a cylindrical steel autoclave with a lid which is bolted in place, is heated on an electric hot plate in a furnace cavity, the temperatures of the solution opposite the quartzite and opposite the seed crystals being measured by thermo-couples strapped to the external surface of the autoclave. The seed crystals are rectangular plates having their major surfaces perpendicular to the Z axis, and are suspended one above the other by platinum wires. The quartzite is crushed into particles and sieved to obtain particles of a size to give the desired rate of growth. Sufficient quartzite is used so that one third remains unused when the crystals have grown to the desired size. The total surface area of the quartzite particles is chosen, after experiment, so that the required temperature difference between the solution around the quartzite and that around the seed crystals, is obtained. Specifications 792,724, 797,203 and 811,215 also are referred to.