ThCr2Si2-type

REFC2B2 (ThCr2Si2 type) CaRh2B2 type Isolated B atoms... 

In the review by Kanatzidis et al. (2005), the preparation by the tin-flux method is mentioned also for several ternary phosphides and polyphosphides of rare-earth and transition metals. Typically the components (R metal, T metal, P and Sn in an atomic ratio of about 1 4 20 50) in sealed silica tubes were slowly heated, to avoid violent reactions, up to 800°C, annealed at that temperature for 1 week and slowly (2 K/h) cooled to ambient temperature. The tin-rich matrix was dissolved in diluted hydrochloric acid. The authors described the preparation of compounds corresponding for instance to the formula MeT4P12 (Me = heavy rare-earth metals and Th and U, T = Fe, Ru, etc.) and to the series of phases MeT2P2 (Me is a lanthanide or an actinide and T a late transition metal) having a structure related to the BaAl4 or ThCr2Si2 types. 

ThCr Si2, tllO structural-type (a BaAl -derivative type) The ThCr2Si2-type structure is one of the ordered ternary variant of the BaAl4 type, frequently found in several ternary compounds. 

The ThCr2Si2 More than 400 compounds of AB2X2 stoichiometry adopt the ThCr2Si2 type struc-... 

Eu-Ni-Sb. Marchand and Jeitschko (1978) investigated the crystal structure of the EuNi2Sb2 compound (ThCr2Si2 type structure a = 0.43834, c = 1.0664 X-ray powder diffraction). Stoichiometric amounts of the elemental components (Eu, Ni better than 99.5%, Sb better than 99%) were sealed under argon in silica tubes, heated at 920 K for 12 h, followed by 4 h at 1250 K and rapid cooling. The samples were then ground to powder, cold pressed to... 

FIGURE7 (a) GCIC02B2 has the ThCr2Si2-type structure, where Gd resides on the Th, Co on the... 

Furthermore Si2 analogous to 02 has been detected in Li2Si119 and ternary ThCr2Si2 type silicides such as SrAg2Si2120l The relatively short SiSi distances of 2.37 and 2.33 A may indicate some degree of covalent MSi bonding or even tt contributions in the SiSi bond. 

There are no sharp metal boron ratios for which the transition from isolated boron atoms to boron pairs to boron chains and so on occurs. For example, isolated boron atoms solely occur in borides, crystallizing in the relatively metal-poor REFC2B2 (ThCr2Si2)-type structure (M/B = 1.5), while... 

From X-ray powder analysis Mayer et al. (1973) reported CeAu2Si2 to crystallize with the ordered ThCr2Si2-type of structure I4/mmm, a = 4.326(5), c = 10.24(5). For sample preparation, see LaAu2Si2- Antiferromagnetic ordering was observed by... 

Various authors agreed on the existence of CeNi2Si2 with the ThCr2Si2-type (see also table 3) a series of physico-chemical properties have been studied, i.e. the valence of Ce (Levin et al., 1981), band structure (Koterlin et al., 1981 Koterlin, 1981), electrical and magnetic properties (Bodak et al., 1977 Levin et al., 1977 see also table 4). 

Mayer and Felner (1977) prepared EuCojSij with the ThCr2Si2-type of structure (I4/mmm, a = 3.921(5), c = 9.850(5) X-ray powder analysis). For sample preparation, see EuCu2Si2. Starting materials were 99.9% pure. From Mossbauer effect measurements Eu was said to appear in two valence states. The thermoelectromotive force (80-1050 K) was investigated by Levin (1981). 

According to X-ray powder diffraction data by Ballestracci (1976), EuPdjSij is body-centered tetragonal with the ordered ThCr2Si2-type, I4/mmm, a = 4.190 and... 

According to X-ray powder data by Rieger and Parthe (1969), GdCr2Si2 crystallizes with the ThCr2Si2-type of structure [I4/mmm, a = 3.944(6), c = 10.672(10)]. Samples were arc melted and subsequently annealed in evacuated silica tubes at 900 °C for 100 h. 

Rossi et al. (1979) by means of X-ray powder diffraction concluded GdIf2Si2 to be isostructural with the ThCr2Si2-type of structure (space group I4/mmm, a = 4.063 and c = 9.952, = 12.08 kg/dm ). For sample preparation, see CePd2Si2- Slaski... 

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