Crystal Structures and Stabilities of gamma-and. gamma '-Brass Phases in Pd(2-x)Au(x)Zn(11) (x=0.2-0.8): Vacancies vs. Valence Electron Concentration

TitleCrystal Structures and Stabilities of gamma-and. gamma '-Brass Phases in Pd(2-x)Au(x)Zn(11) (x=0.2-0.8): Vacancies vs. Valence Electron Concentration
Publication TypeJournal Article
Year of Publication2011
AuthorsThimmaiah S, Crumpton NA, Miller GJ
Journal TitleZeitschrift Fur Anorganische Und Allgemeine Chemie
Volume637
Pages1992-1999
Date Published11
Type of ArticleArticle
ISBN Number0044-2313
Accession NumberWOS:000298171900008
Keywordsalloy, approximants, cd, Gamma brass, hume-rothery compounds, hume-rothery phase, PD, phase width, quasi-crystal, system, x-ray, x-ray diffraction, ZINC, zn
Abstract

To probe the effect of valence electron concentration (vec or e(-)/atom) on gamma-Pd(2+x)Zn(11-x) phases a series of compounds Pd(2-x)Au(x)Zn(11) (x = 0.3-0.8; e(-)/atom = 1.70-1.75) was synthesized and structurally characterized. The gold-substituted.-brass type phase was observed for x <= 0.3, having a refined composition of Pd(1.93)Au(0.27(1)) Zn(10.80(1)) (space group I (4) over bar 3m; a = 9.0953 (2) angstrom). Further addition of gold (0.4 <= x <= 0.8) leads to a 2 x 2 x 2 superstructure of the.-brass type phase (denoted as the. gamma-phase), with noticeable phase width (F (4) over bar 3m; 18.1827(4)-18.1799(4) angstrom). The. gamma-phase consists of four independent 26-atoms clusters, which are arranged around four distinct high symmetry points. The structural stability and phase width of. gamma-phase are primarily controlled by two of these clusters, both of which show mixed occupancies and occurrence of non-stoichiometric vacancies. Amongst all the observed. gamma-phases in the Pd-Au-Zn system, the vacancy concentration increases with increasing values of gold substitution. The vec of all observed. gamma-phases fall between 1.636 and 1.654 e(-)/atom values, which are greatly influenced by the nonstoichiometric vacancies present in the structure.

DOI10.1002/zaac.201100357
Alternate JournalZ. Anorg. Allg. Chem.