In situ and ex situ investigation of the displacive phase transformations Ag 3 Sn(h) → Ag 3 Sn(l) and Ag 3 Sb(h) → Ag 3 Sb(l)

✍ Scribed by Ellner, M.; Mittemeijer, E. J.

• Book ID: 118043517
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2003
• Tongue: English
• Weight: 145 KB
• Volume: 218
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.218.10.675.20764

✦ Synopsis

Abstract

The occurence of the polymorpic phase transformations Ag~3~Sn(h) → Ag~3~Sn(l) and Ag~3~Sb(h) → Ag~3~Sb(l) was demostrated in situ primarily by means of high-temperature X-ray powder diffracion and thermal analysis as well as by ex situ X-ray powder diffraction. Both solid- and liquid-quenched aloys were investigated. The structure of the high-temperature phases Ag~3~Sn(h) and Ag~3~Sb(h) is isotypic with Mg (Pearson symbol __hP__2, space group __P__6~3~/mmc); unit cell parameters are: a = 2.9863(8) Å, c = 4.784(2) Å for Ag~3~Sn(h) and a = 2.9944(9) Å, c = 4.812(3) Å for Ag~3~Sb(h). The low temperature phases Ag~3~Sn(l) and Ag~3~Sb(l) are orthorhombic displacive homeotypes of the hexagonal close-packed structure, isotypic with with β-TiCu (__oC__4, Cmcm). The unit cell parameters are for Ag~3~Sn(l): a = 2.9973(5) Å, b = 5.1618(8) Å, c = 4.786(1) Å, b/a = 1.722 < √3; and for Ag~3~Sb(l): a = 2.9947(3) Å, b = 5.2497(5) Å, c = 4.8495(7) Å, b/a = 1.753 > √3. The crystal structures and the phase transformations werde discussed in terms of the valence electron concentration.