Tokaychuk I. Systems Hf-Ga-{Si,Ge,Sn,Sb}: phase equilibria and crystal structures of the compounds

The phase equilibria in the systems Hf-Gа-{Si,Ge,Sn,Sb} at 600°С were investigated in the whole concentration region with the use of X-ray phase, structural and local spectral analyses. The isothermal sections of the corresponding phase diagrams were constructed for the first time. The existence of 27 binary compounds has been confirmed and 13 ternary compound were found. Their crystal structures were determined and analyzed. By means of X-ray single crystal diffraction the crystal structure of the compound Hf3Ga1,97(2)Sn1,03(2) was determined. It is the first representative of new structure type, which is an ordered derivative of the ThIn type. The homogeneity ranges of the ternary compounds and the boundaries of the solid solutions based on all binary compound were determined as well as the mechanisms of their formation were established. The crystal chemical relationships between the synthesized compounds were determined and the group-subgroup relationships between related structures were derived. The concentration ranges of the investigated systems with the Hf content from 0 to 50 at.% characterize by absence of the solubility of third component in the binary compounds. In the ranges with Hf content from 50 to 100 at.% the formation of the extended solid solutions based on the binary compounds including continuous solid solutions was observed. In the structures of the compounds existing in the first range, the atoms of the p-block elements form statistical mixtures, whereas in the second range a tendency towards their ordering is observed. Small-size atoms characterize by three types of coordination polyhedra: trigonal prisms, octahedra, and tetragonal antiprisms.