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Large single crystals of mercuric iodide from the vapour phase; preparation of a space experiment

Authors
Journal
Journal of Crystal Growth
0022-0248
Publisher
Elsevier
Publication Date
Volume
99
Identifiers
DOI: 10.1016/s0022-0248(08)80125-x

Abstract

Recently, the vapour growth of large single crystals has been recognized as an attractive new field in materials research under microgravity conditions and mercuric iodide as a model substance for the growth experiments in space. Presently we are involved in the development of a sophisticated growth facility for the European Space Agency in which long-term (up to 6 months) vapour growth (computer controlled) experiments can be performed under microgravity conditions (telescience). There are several prerequisites in the development of this facility, which have been identified as separate technical or scientific tasks of the project and are discussed in this paper: (1) high resolution in situ measurements of the growth rate of the crystals as a function of crystallographic orientation, (2) crystal surface temperature measurements for evaluation of the actual supersaturation, which is the driving force for the growth, (3) a cooling system capable adjusting the cooled area to the increasing crystal size (in order to avoid thermal stresses in the crystal). For automatic control of the growth, the dependence of the growth rate on supersaturation for various starting materials (doping, nonstoichiometry) has to be known in advance; for this purpose the transport rate will be measured in a separate precursor space experiment (DCMF).

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