A-ThSij type

From DTA measurements Ishikawa et al. (1983) reported a congruent melting behavior for the compound CeCuQ jSij 5 with a melting temperature of 1785 + 15 °C. CeSi, gCuo2 (a-ThSij-type) orders ferromagnetically at = 6.5 K (Ishikawa et al., 1983) ... 

A complete solid solution (Ce, Sm )Si is formed crystallizing with the FeB-type of structure (Pnma). At 600°C SmjSij (defect AlBj-type) dissolves up to 9 a/o Ce. For the disilicide region Ce, j Sm Si2, a continuous transformation from the tetragonal a-ThSij-type (CeSij) to the orthorhombic a-GdSij-type (SmSij) was... 

No ternary phase diagram exists for the Eu-Ca-Si system the stability range of the a-ThSij-type structure was investigated along the concentration section Ca,.. Eu Si2 in the pressure range up to 40 kbar (quenched from 1000-1500°C). For sample preparation, see Eu-Sr-Si. 

Due to the polymorphic transformation of the a-ThSij- and GdSij-type as a function of temperature and concentration, the phase relations in the disilicide and digermanide region are rather complex. The diverging results obtained by Haschke et al. (1966), Mayer and Eshdat (1968), Muratova and Bodak (1974) and Bodak and Muratova (1979) are the expression of this complicated matter. Basic agreement however exists about the formation of a continuous solid solution CeGe2., Si. In... 

Mayer and Eshdat (1968) independently investigated the structural behavior in the pseudobinary system CeGe2 (Si,j by means of X-ray powder data. For sample preparation, see NdGe2 j,Si. Ge-rich alloys were said to adopt the GdSij-type (Imma) and furthermore a continuous transformation into the tetragonal ThSij-type of structure (14j/amd) was proposed for alloys richer in Si. The variation of the lattice parameters versus x is shown in fig. 10, the linear variation of the unit cell volume in fig. 11. Both functions are similar to those reported by Haschke, but no discontinuities were recorded and no three-phase or two-phase equilibria involving two separate phase solutions were observed. See also the discussion for NdGc2, jSi. ... 

Mayer and Tassa (1969) investigated the phase equilibria within the concentration section SmNi Si2 ,. by means of X-ray powder analysis. For x < 0.4 the ThSij-type of structure was found to be stable. SmNio.4Sii crystallizes with the AlB2-type of structure (see table 27). In analogy to the X-ray powder data of NdNig Sij a statistical distribution of Ni/Si atoms in the 2d site of P6/mmm was assumed. Ni/Si atom ordering, however, seems to be likely (see also Mossbauer data of isotypic LaFcQ4Si, j). 

The ternary compounds (l) GdGe2Al2 with the La202S anti-type structure, a = 4.248, c = 6.714 was found by Zarechnyuk et al. (1970b) (3) GdGeAl with a-ThSij structure type, o = 4.152, c = 14.421, reported by Ryabokon (1974). (2) GdGc2Al with an undetermined crystal structure together with a partial phase diagram (fig. 48) was reported by Zarechnyuk et al. (1981). 

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