The thermal expansion of quartz by x-ray measurements

Abstract

The study of the coefficients of thermal expansion of substances has in the past, for the most part, been confined to direct measurement by optical methods. At the present time X-rays are being used for determining the expansion of the atomic lattice as distinct from the specimen block. A question has arisen as to tire relation between the coefficient of expansion as measured visually and that measured by X-rays. From theoretical considerations Zwicky* has predicted that the two are not identical. X -ray measurements on the thermal expansion of single crystals of bismuth by Goetz and Hergenrothers have shown that there is a difference between the values obtained by the two methods of measurement. On the other hand Y. Tu finds no evidence in his experiments on rock salt of the secondary structure described by Zwicky. The question to be answered is thus one of great importance. the present paper gives evidence to shown that for silver and quarts there is no difference between the coefficients of expansion as measured by X-rays and those from optical measurements. The work described in this paper was carried out to measure the thermal expansion of quartz by X-rays and by comparing the results with those from optical measurements to test the validity of the assumption, made in previous papers, that the coefficient of thermal expansion of silver is the same whether measured by X-rays or optical methods.