The tin-rich part of the Au-Pt-Sn system

The phase relations in the till-rich section (greater than or equal to 50 a t.% Sn) of the system Au-Pt-Sn have been studied by powder X-lay diffractio n, metallography, electron microprobe analysis and thermal analysis. The co ndensed phases occurring, tie-lines and tie-triangles are presented for an isothermal section of the tin-rich part of the phase diagram at 400 degrees C. There is a limited solid-solubility exchange between Au and Pt in most o f the binary phases; however, for AuSn and Pt2Sn3 the ranges of homogeneity are appreciable. Up to 50% of the gold in AuSn can be replaced by platinum and up to ca. 20% of the platinum in Pt2Sn3 can be replaced by gold. A new ternary phase (attributed the formula AuPt2Sn3) has also been discovered, with a homogeneity range in the Au-Pt dimension between Au137Pt293Sn570 and Au196Pt241Sn563. AuPt2Sn4 is C-centred monoclinic with unit-cell dimension s a = 543.1(1), b = 537.3(1), c = 931.3(1) pm and beta = 101.17(1)degrees. (C) 2001 Elsevier Science B.V. All rights reserved.