ZrNiAl-type

Fig. 10. ZrNiAl-type hexagonal crystal structure of RCuAl.

Compounds with the Fe2P (ZrNiAl) type of structure... 

The crystal structure of URhIn is the hexagonal ZrNiAl type structure also present in UNiGa and UNiAl. Specific heat suggests 7n = 6.5K and susceptibility peaks at 7K. The p.SR relaxation rate of electronic origin, however, remains low and temperature independent down to 2.6 K. This completely contradicts the bulk data and the nature of the magnetic anomaly at 6.5 K remains unsolved. 

The aluminides with nickel and copper as transition-metal component show a very interesting behavior. At normal pressure conditions, YbNiAl (Schank et al. 1995, Rossi et al. 1983a,b) and YbCuAl (Mattens et al. 1982) crystallize with the hexagonal ZrNiAl type (Krypyakevich et al. 1967, Jacob et al. 1987, Zumdick et al. 1999) (fig. 3), a ternary ordered version of the Fe2P structure (Rundqvist and Jellinek 1959) (space group P62m). 

Martens et al. (1977, 1980a,b) assumed the Fe2P-type structure for NP-YbCuAl, while Dwight et al. (1968) indicated the ZrNiAl type, assuming an ordering of the copper and aluminium atoms on the iron and phosphorous sites. At this point it is worthwhile to note that such an ordering is only evident from small changes of the intensities in the X-ray... 

The silver silicide (landelli 1985) shows an ordering between the silver and silicon atoms. It crystallizes with the ZrNiAl type. This is one of the rare cases where the silver atoms show no random distribution within the polyanion. 

For Nialn-type YbCuSi (landelli 1983), the ytterbium valence is 4-3 in the temperature range 80-300 K, leading to a formulation Yb Cu Si . The same holds true for YbAgSi with ZrNiAl type structure (landelli 1985). 

YLiSi crystallizes with the ZrNiAl-type of structure (ordered Fe2P-type, P62m, a = 7.023, c = 4.212, = 3.51, p = 3.43 kg/dm ). The structure was refined from... 

YLiGe was found to adopt a ZrNiAl type with lattice parameters a = 0.7065, c = 0.4233 (Czybulka et al. 1979). The measured and X-ray-derived densities were 4.56 gcm and 4.58 gcm , respectively. The alloy was prepared by heating the elements in the stoichiometric ratio 1 2 1 in a Ta crucible under dry Ar to a temperature above 1000 K. The sample was annealed under unspecified conditions until only YLiGe and excess Li were detected by X-ray analysis. The stoichiometry was confirmed by chemical analysis (33.3 at.% Y, 32.0 at.% Li and 34.7 at.% Ge). The purity of the starting components is unstated. 

ErLiGe (2) was found to crystallize with a ZrNiAJ type with lattice parameters a= 0.7005, c=0.4214 (Pavlyuk 1989 Pavlyuk et al. 1991a) from X-ray powder diffraction of arc melted in a purified Ar atmosphere under a pressure of 1.01 x 10 Pa samples which were annealed in Ta containers at 470 K for 240 h. Purity of the starting components was 99.82 mass% Er, 98.2mass% Li and 99.999 mass% Ge. Czybulka et al. (1990) confirmed the crystal structure for the compound of equiatomic composition, ZrNiAl type, a = 0.6985, c = 0.4219 (X-ray single-crystal data). Chemical analysis gave 33.6 at.% Er, 32.4 at.% Li and 34.0 at.% Ge. For sample preparation, see Ho-Li-Ge. 

Grund et al. (1986) reported the crystal structure of the YbLiGe (1) compound ZrNiAl type, a=0.6939, c = 4183. The measured density was 7.18 gcm and the X-ray density 7.21 gcm. Results of chemical analysis confirmed the stoichiometry and gave... 

---