Chemical composition topography in RE hexaboride crystals obtained by various solution-melt methods

An extensive step-by-step study of the chemical composition of rare-earth metal (RE) hexaboride single crystals and their solid solutions has done. The EDX and WDX methods were used for this study. The composition topography of the surface has been investigated in two directions: along the length and breadth of the crystals. It was done for two times: after separation from the Al matrix and after an additional etching and polishing. There was a considerable dispersion of data in the crystals obtained using the solution-melt methods (the conventional and the immiscibility gap method), and also the liquid-phase method (floating zone). An assumption that the direction of growth of single crystals is opposite to the direction of monotonic change of the boron content has been suggested. We have concluded that all single crystals of RE hexaboride grown by different methods are significantly different on composition. This conclusion was made due to the respective relative position of the stoichiometry line and the homogeneity region of the compound which crystals have been obtained.

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