Abstract
Very small elastic strains (tilts of the order of 0.25 sec of arc and dilationsΔd/d≃10−6, whered is the spacing of net planes) have been observed in natural quartz crystals. According to their rocking curves which are of almost theoretical width, these crystals were commonly expected to be practically perfect crystals. On double crystal X-ray topographs a pattern was revealed of uniformly strained layers parallel to the rhombohedron faces (10¯11) and with thickness ranging between 20 and 200 microns. This fine structure strain pattern was correlated to the pattern of the optical coloration which could be produced by irradiating the originally transparent crystals with X-rays. A localincrease of coloration matched with a localcontraction of the lattice. Tilts occurred in transition zones between adjacent layers with slightly different lattice spacings. Strain and coloration patterns probably have as a common cause the deposition of layers with different impurity concentrations during the growth process of the crystals. Although no change of the strain as a result of the X irradiation could be detected in the colored layers in particular, experimental evidence has been found for anoverall expansion of the lattice of the order ofΔd/d≃5×10−7 due to X irradiation. This expansion seems to saturate at this low value and is probably caused by electronic processes connected with the coloration. Some aspects concerning the nature of the color centers have been discussed. It seems likely from the results of the strain measurements that both sets of layers, colored and transparent ones, play a combined role in coloration.
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Dedicated to ProfessorEugen Kappler on the occasion of his 60th birthday.
On leave from Physikalisches Institut der Universität Münster, Münster (Westf.), Germany.
My thanks are due to Dr. R. D.Deslattes, United States National Bureau of Standards, Washington, for providing the samples and drawing the attention to the strain pattern in them. I would also like to thank Dr. M.Hart for valuable discussions.
This work was supported in part by the Advanced Research Projects Agency and the General Electric Advanced Electronics Center at Ithaca, N.Y., USA.
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Bonse, U. Elastic strain and coloration pattern in natural quartz crystals. Z. Physik 184, 71–84 (1965). https://doi.org/10.1007/BF01380669
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DOI: https://doi.org/10.1007/BF01380669