Phase states and the mechanism of crystallization of condensed Ar-Kr mixtures

The structure characteristics of Ar-Kr mixtures deposited under special conditions have been investigated in the whole interval of concentrations applying the transmission electron diffraction technique (THEED). The samples were prepared in situ by condensing a gas mixture preliminary cooled down to the sub-liquid-nitrogen level onto substrates at T = 6 K and 20 K. The experimental results show that the structure and morphology of the Ar-Kr condensates are dependent on the nucleation dynamics prevailing in the course of the sample formation. It is shown that cooling a gas mixture is favorable to the clusterization of solute atoms in the gas flow. The krypton small clusters can serve as condensation clusters. The phase boundaries of the condensates have been determined. Regular Ar-Kr solutions are formed when the contents of one of the components are low (0-10 mol % Ar), (0-5 mol % Kr). The diffraction patterns of the condensates with prevailing Kr contents corresponded to a mixture of Kr-enriched fcc solutions and a dispersed phase of argon. The excess Kr contents are due to the specific morphology of the solutions dictated by condensation conditions. The Ar-based samples contained a mixture of two crystalline phases (an fcc solution and the hcp phase of nearly pure argon) and a glass phase of nearly pure krypton. In the concentration range 58-78 mol % Ar the new morphological form of the Ar-Kr condensates resembles the gel. The phase state diagram of the Ar-Kr condensates has been obtained.& nbsp;Published under an exclusive license by AIP Publishing