New refinements of the γ brass type structures Cu5Zn8, Cu5Cd8 and Fe3Zn10

Abstract

The crystal structures of CusZn8, CusCds and FeaZna0 have been studied using single-crystal X-ray diffraction techniques. All three alloys have the body-centred cubic space group 1743m with four formula units per unit cell. Lattice parameters are 8.878 (4), 9.615 (10) and 9.018 (3) A respectively for CusZn8, CusCd8 and the pseudocell of FeaZn~0. Evidence shows a new superstructure of 36 A at the composition FeaZn~0. Values of lattice parameter as a function of composition are given for the CusCd8 phase. New data are presented on the three structures, and the ordering of the alomic species is compared with that reported by previous workers. Significant differences in our ordering for FeaZn~0 are attributed to our different composition within the 7 phase. X-ray diffraction intensity data were collected using a 3-circle automatic single-crystal diffractometer and Mo Ke X-radiation. The crystal structures were refined using full-matrix least-squares methods to final R values of 6.1%, 7-5 %, and 5.5 % respectively. A discussion of possible reinterpretations for these and other ~, brass structures is presented.

Structure of the cubic iron–zinc phase Fe22Zn78

“…Comparison with the structure of the F phase, Fe3Zn~0, shows that the lattice constant of F 1 is almost exactly twice the lattice constant a = 8.982/~ of the F phase. As was demonstrated by Brandon et al (1974) this packing is of the 7-brass type, with space group I43m, if we neglect superstructure. If we stack eight cells of the F phase together, doubling the cell in the x, y and z directions, a large cell with space group F43m is formed.…”

“…If we stack eight cells of the F phase together, doubling the cell in the x, y and z directions, a large cell with space group F43m is formed. When we compare the list of coordinates of the atoms in this supercell, using the structure determination by Brandon et al (1974), it is evident that the F and F~ structures have much in common. The atoms 1, 3, 4, 6, 8, 9, 10, 11, 12 and 14 have almost the same positions.…”

“…The cubic phase Fe3Znl0, commonly called F, was investigated by Brandon, Brizard, Chieh, McMillan & Pearson (1974), and shown to be of the ),-brass type; weak superstructure reflections, however, indicate that IRON-ZINC Fe22ZnT8 the structure is more complicated. Bastin, van Loo & Rieck (1974) discovered a cubic phase slightly richer in Zn, which they called F~.…”

Fe-Zn intermetallic phases prepared by diffusion annealing and spark-plasma sintering

“…The G phase is bcc with the g Cu 5 Zn 8 brass type and I m 43 space group. Concerning the stoichiometry, Brandon et al 14 indicate that it is Fe 3 Zn 10 (ICSD code 2094), Belins 15 give Fe 13 Zn 39 (ICSD code 150198) and Johansson et al 16 give Fe 4 Zn 9 (ICSD code 103708). Employing the CIFs for all these four stoichiometries, we obtained virtually the same refined lattice parameter of a = 0.8972 nm, but the correspondence between the structural model and the measured data was the best for the Fe 13 Zn 39 stoichiometry.…”

High-Accuracy X-Ray Diffraction Analysis of Phase Evolution Sequence During Devitrification of Cu50Zr50 Metallic Glass

“…1-The equilibrium Cu-Zr Phase Diagram. [22] [29,30] Cu 7 Zr 2 * C2/m [31] Cu 3 Zr* P6 3 /mmc [32] Cu 8 Zr 3 Cu 8 Hf 3 Pnma [29,33] Cu 2 Zr Fd3m [34] Cu 24 Zr 13 [35] Cu 10 Zr 7 Ni 10 Zr 7 Aba2 [27,29] Cu 10 Zr 7 Cmca [36] Cu 10 Zr 7 Pbca [37] Cu 11 Zr 9 I4/m [38] CuZr CsCl B2 Pm3m [39] CuZr* B19¢ P2 1 /m [40] CuZr* B33 Cmcm [41] CuZr* c-CuTi B11 P4/nmm [42] CuZr* AuCu-I L1 0 P4/mmm [42] CuZr* b-AuCd B19 Pmma [42] Cu 5 Zr 8 R3m [43] Cu 5 Zr 8 I43m [44] Cu 5 Zr 8 [35] bCuZr 2 MoSi 2 C11 b I4/mmm [45] bZr W A2 Im3m [42] aZr* Mg A3 P6 3 /mmc [43] 0.2 lW, respectively. For each specimen analyzed, multiple scans were performed, and the second scan was taken as an instrument baseline.…”