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Hochdrucksynthese und kristallstruktur von Pd8Al21, Pd8Al17Si4 und Pt8Al21

1988; Elsevier BV; Volume: 136; Issue: 2 Linguagem: Inglês

10.1016/0022-5088(88)90431-6

1878-2728

Klaus‐Jürgen Range, Ernst G. Christl,

Quasicrystal Structures and Properties

Die intermetallischen Phasen Pd8Al21, Pd8Al17Si4 and Pt8Al21 wurden aus den Elementen durch Hochdruck-Hochtemperatursynthese in einer modifizierten Belt-Apparatur dargestellt. Die isotypen Verbindungen kristallisieren tetragonal, Raumgruppe I41a, Z = 4, mit den Gitterkonstanten a = 12.962(2)Å, c = 10.684(2) Å (Pd8Al21), a = 12.962(3) Å, c = 10.682(2) Å (Pd8Al17Si4) und a = 12.949(3) Å, c = 10.659(3) Å Pt8Al21 In der komplizierten Kristallstruktur sind die Ubergangsmetallatome 10-fach von Aluminium (bzw. Silizium) koordiniert, die Al-Atome (mit Ausnahme der Punktlagen Al(1) und Al(5)) sind von vier Schwermetallatomen umgeben. Pd8Al21, and Pd8Al17Si4 sind echte Hochdruckphasen and unter Normalbedingungen nur metastabil. The intermetallic phases Pd8Al21, (Pd8Al17Si4) Pt8Al21 were synthesized from the elements by high pressure-high temperature synthesis in a modified belt-type apparatus. The isotypic compounds crystallize in a tetragonal struc ture with space group I41a, Z = 4, with lattice constants a = 12.962(2) Å, c = 10.684(2) Å (Pd8Al21), a = 12.962(3) Å, c = 10.682(2) Å (Pd8Al17Si4) and a =12.949(3) Å, c = 10.659(3) Å Pt8Al21 In the complicated crystal structure, the transition metal atoms are 10-fold coordinated by aluminium (or silicon); the aluminium atoms (except at atomic positions Al(1) and Al(5)) are surrounded by four heavy metal atoms. Pd8Al21, and (Pd8Al17Si4) are true high-pressure phases, being only metastable under normal conditions.