| 摘要 |
<PICT:0680773/III/1> Quartz is grown by supporting one or more quartz seeds in a container above a nutrient mass of quartz particles, the seeds and nutrient being in contact with a single - phase aqueous medium containing sodium ions and having a specific volume not greater than approximately 1.67 times that of the aqueous medium at normal temperature, the temperature in all parts of the container being at least 375 DEG C, in the region of the nutrient at least 380 DEG C and in the region of the seeds a few degrees, preferably not more than 5 DEG C, higher than the temperature in the region of the nutrient. The sodium ions may be derived from sodium hydroxide, carbonate, silicate or other sodium salts, particularly salts of weak acids, and the aqueous medium may contain a small concentration, e.g. 0.001-0.005 normal, of e.g. sodium oleate. The sodium-ion concentration is preferably at least 1/2 normal. Suitable apparatus comprises an expendable container 1 fitting closely into the bore of a heavy cylinder 14 closed by end caps 15, 16. Intermediate caps 17, 18 fit into the ends of the container 1 and the cap 18 is bored at 19 to provide a safety vent should the container 1 rupture. Quartz particles (size about 1/2 -inch diameter) are placed in the container 1 together with one or more quartz seeds supported by a stirrup 10. The seeds may have their faces perpendicular to the crystal axis or parallel to a major rhombohedral face. The crystal axis may be parallel to or at an angle to the axis of the container, at least 60 per cent and preferably 80 or 90 per cent of the remaining free space in the container is then filled with the aqueous medium and the container sealed and inserted in the cylinder 14 which is then stood on a hot plate in an insulated container (see Group XI). The insulation is arranged to allow heat to be dissipated from the upper part of the cylinder 14 to give the required temperature gradient. The temperature in the hottest part of the container should not exceed 550 DEG C and the temperature difference between seeds and nutrient should preferably be not more than 5 DEG C, estimated by external measurements at levels A and B, to avoid spurious seeding. Growth rates of 0.09 and 0.04 inches per day are referred to in examples. |
