Production Of High-Purity Cadmium Single Crystals By Vertical Directed Crystallization Method

Abstract

The process of producing high-purity Cd crystals by the vertical directed crystallization (VDC) from a melt according to the Bridgman method is investigated. Single crystals with the preferred growth direction and were produced. The angles of deviation of the growth direction relative to the axis of the samples are α = 27.2° and α = 0.5°. The crystal perfection, microstructure and microhardness of the grown crystals are determined. As shown by x-ray diffraction analysis, in this VDC variant of high-purity cadmium, a perfect single-crystal structure is not reached. In the start section there are separate grains with different orientations, the amount of which decreases in the end section of the single crystal. This results in the formation of a more perfect single-crystal structure with a preferred orientation, which occupies the entire cross section of the crystal. The microhardness of the upper and lower sections of single crystals was determined. The more contaminated end sections of the crystals have lower microhardness than the initial parts. The impurity composition of the start and end sections of single crystals produced from cadmium of various grades purity was studied. The efficiency of impurity elements redistribution along single crystals is the same for different grades of cadmium. The developed VDC process can be used for growing single crystals of low-melting metals, such as Zn, Pb, Te, In, Bi, Sn, etc.