Growth of large quartz crystals.
TL;DR: Alternative methods employing a temperature gradient, such as Spezia4 used in his pioneer experiments are re-examined, finding them to be unsatisfactory.
Abstract: DURING recent years there has been considerable interest both in Europe and the United States in the synthesis of quartz crystals large enough for use as piezo-electric oscillators in telecommunication equipment. An isothermal process for growing such crystals was described by Nora and W. A. Wooster1 in 1946 and a similar method was developed independently in Germany during the Second World War by Nacken2. The isothermal process depends on the high solubility of silica glass relative to that of α-quartz under hydrothermal conditions. In our most successful experiments we were able to deposit a total of nearly 1 mm. of good-quality quartz on to a seed crystal, cut parallel to a rhombohedral face, in an 18-hr, growth-cycle. However, difficulties were incurred in attempting to prolong the growth-cycle beyond a day, due to the devitrification of the silica glass3. We therefore re-examined alternative methods employing a temperature gradient, such as Spezia4 used in his pioneer experiments.
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TL;DR: In this article, it was shown that the appearance of electrical twinning on the growing faces of the quartz crystals can be caused by corrosion of steel in alkaline solution, which was a rather unexpected problem, since in high-pressure steam boilers alkali is added in small amounts to prevent corrosion of the boiler tubes.
Abstract: Research at the Bell Telephone Laboratories on the problem of growing large single crystals of quartz has now progressed to a point where it is possible to grow crystals weighing more than 1 lb. each in a period of 60 days or less. Equipment now in use includes autoclaves 4 inches in inside diameter and 4 ft. long, weighing about 1150 lb. each. In developing the hydrothermal process used to grow these quartz crystals it has been necessary to solve many problems in the little-known field of high pressure. The results point to the possibility of growing other types of crystals, and the field of usefulness of this process now appears to be much more extensive than was the case at the beginning of the investigation in 1946. Of prime importance is the fact that crystals grown from solution are likely to be better formed and of more perfect quality than those grown from the melt or by other methods. Many of the difficulties inherent in this work have been due to corrosion of steel in alkaline solution. This was a rather unexpected problem, since in high-pressure steam boilers alkali is added in small amounts to prevent corrosion of the boiler tubes. Such corrosion has been shown to be responsible for the appearance of electrical twinning on the growing faces of the quartz crystals. Other causes of such twinning have also been found in the course of this work.
49 citations
TL;DR: The history of quartz crystal growth is reviewed from the origin to the industrialization in this article, where the developing process of growth techniques is divided into the following three stages: (1) The fundamental work based on the mineralogical genetic view point, which was performed in Italy during the end of the 19th to the beginning of the 20th centuries.
48 citations
TL;DR: In this article, it was shown that the steps between successive successive turns are exactly one unit cell high, and that this is true in many cases, although of several unit cells high are not exceptions.
Abstract: GROWTH spirals, as predicted by F. C. Frank's theory1 on crystal growth, have been observed on the c (0001) faces of carborundum by Ajit Ram Verma2 and by S. Amelinckx3. The steps between successive turns, as stated by Frank, are exactly one unit cell high. This seems, in fact, to be true in many cases, although of several unit cells high are not exceptions.
24 citations
TL;DR: In this paper, the effects of various baffles on the fluid flow and temperature fields in an industry-size autoclave were investigated and it was shown that changing the baffle hole opening and the number of holes on a baffle are effective ways to control the temperature uniformity in the growing chamber.
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TL;DR: In this article, the authors have repeated Spezia's experiments so far as to confirm his results, but the period of months which is required for appreciable growth to occur makes the method unsuitable for industrial production.
Abstract: THE extensive use of quartz in piezoelectric oscillators has stimulated the production of synthetic quartz crystals Spezia1 in 1906 grew quartz at a temperature somewhat below 300° C from an aqueous solution containing sodium metasilicate and sodium chloride His method was to dissolve quartz in the hotter part of the container and deposit it in the cooler part We have repeated Spezia's experiments so far as to confirm his results, but the period of months which is required for appreciable growth to occur makes the method unsuitable for industrial production
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