THE BINARY-SYSTEM PT-SN

The system Pt-Sn was completely revised over narrow intervals of composition (1-2 at.% Sn), using more than 60 carefully annealed alloys (more than 3000 h at T>600 degrees C), measured with differential thermal analysis, X-ray diffraction and electron microprobe analysis. The five stoichiometric intermediate phases have generally higher melting points than previously indicated in the literature for Pt3Sn (1402 degrees C) and PtSn (1276 degrees C) and higher peritectic decomposition temperatures for Pt2Sn3 (898 degrees C), PtSn2 (748 degrees C) and PtSn4 (540 degrees C). The intermediate phase PtSn has a structure similar to PtSn3 (P6(3)/mmc), with a strictly stoichiometric composition as shown by electron microprobe and X-ray diffraction methods. The lattice parameters of all intermediate phases in the binary system PtSn have been calculated, showing no detectable variations due to composition. The solubility of platinum in tin is negligible.