Revelation of microtwinning in hydrothermally grown synthetic quartz by growth structures

Abstract

AbstractGrowth structuress on prism surfaces of synthetic quartz grown by hydrothermal crystallization technique, indicative of microtwinning in them are described, illustrated and discussed. The microtwins are revealed by the misorientation of the growth structures, and it is observed that microtwinning is manifested in different forms. Twinned domains appear in the form of strictly oriented, square striated (stepped) structures with inclined surfaces, seemingly overlapping square striated structures, square and irregular regions demarcated by black line‐like boundaries, patch‐like structures enveloping irregularily bound domains, tongue‐like terraces bordered by irregular line of discontinuity of varying height and the regions with both differently shaped as differently oriented growth structures. From the orientations of the square shaped growth structures, it is shown that crystals consist of domains which are in twin relationship to the main crystal. Twins by rotation around an axis perpendicular to (10ī0) with rotation angles of 60°, 90°, and 180° have been observed. Critical examination of some twin boundaries delineated by black line‐like matter, with the application of multiple beam interferometry and FECO reveal that the black boundary is a ridge (line‐elevation). The line elevation along such a twin boundary is explained to be as a result of preferential adsorption of impurity atoms along the trace of the boundary. It is further observed that discontinuity in crystalline structure along the twin boundary leads to growth forms with distorted morphology thus establishing strong dependence of growth forms on the underlying crystalline structure. Causes for generation of the microtwins (twinning on a microscale) in synthetic quartz are discussed.