Abstract

Abstract We carried out experiments of diamond growth in several alkali halides under HPHT conditions of 6 GPa and 1400–1620 °C for 5 h in order to determine whether the halides are active agents in the conversion of graphite to diamond. Growth layers with an order of 1 μm in thickness were detected on diamond seed crystals embedded in the halides. The diamond growth layers were formed even in solid halides, as well as in molten halides. When NaCIO 3 was added to the halides, the growth rate increased drastically. This result indicates that oxygen which contaminates the halides affects the diamond growth, even in the case without intentionally introducing oxygen into the halides, and we propose a model of the diamond growth in the carbon-halides systems that carbon atoms are transported as oxide in the halide media and precipitate on the seed crystal.

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