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Lang X-Ray Topographic Studies of Ruby Grown by Different Methods

Published online by Cambridge University Press:  06 March 2019

Roger F. Belt
Roger F. Belt*
Affiliation:
AIRTRON, A Division of Litton Industries Morris Plains, New Jersey
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Abstract

Crystals of ruby (Al2O3:Cr) are being grown at the present time by several standard procedures, e.g., Verneuil, Czochralski, flux, and hydrothermal. Previous work has indicated wide variations in quality and type of defects. The present study is primarily concerned with ruby grown from PbO-PbF2 fluxes. All crystals were examined in transmission with Mo Kα1 radiation and a Rigaku Denki Lang camera. Samples were either sectioned from larger crystals or obtained as plates with natural growth faces. Results on flux-grown ruby have shown a severely banded substructure due to strain introduced by either the flux or chromium segregation. Crystals with a visible chromium gradient have shown fewer bands in those regions which were depleted of chromium. Annealing studies have been performed on ruby and all banded structure was dispersed into areas of fine particles with a much higher dislocation content. Other features of the substructure are described. These include the observation of Pendellosung fringes in wedgeshaped sections. Areas of nearly 0.5 cm2 were found to be dislocation free. The X-ray results confirm etching experiments but the former yield more information on internal details other than dislocations.

Recent data on sapphire (α-Al2O3) have confirmed several tentative conclusions. Flux grown crystals have some bands due to flux segregation. However, sapphire crystals show higher perfection when compared to ruby. These results have been confirmed by rocking curves obtained on a double crystal X-ray spectrometer used in the parallel position. Measurements on the (00.12) reflection from the natural growth faces were performed with Cu Kα1 radiation. Widths at half the maximum intensity were always found to be larger for ruby than for sapphire. Comparisons were made with respect to a perfect silicon crystal in the same geometry. Some preliminary experiments have been performed on Czochralski ruby prepared by the Linde Company and on hydrothermally grown ruby prepared at Airtron, Examples of defects observed in each case are given. They are highly unique to the growth method. The Lang method is shown to reveal more detail than other X-ray data. A brief discussion of ruby quality as a function of growth method is presented.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 10: Fifteenth Annual Conference on Applications of X-ray Analysis, August 10-12, 1966 , 1966 , pp. 159 - 172
Copyright
Copyright © International Centre for Diffraction Data 1966

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