Synthesis of Pt-Pd antimonide minerals at 1000 °C and the extent of Pt-Pd substitutions

摘要

Phase relations of the Pt-Pd-Sb system were investigated at 1000 °C, with an emphasis on the extent of Pt-Pd substitutions in Pt and Pd antimonide minerals and their stable assemblages. The sealed capsule technique was used, and the reaction products were examined using reflected light microscope, X-ray powder diffractometer, and electron microprobe. Pt-Pd alloy minerals, stumpflite (PtSb), geversite (PtSb2), mertieite II (Pd8Sb3), and stibiopalladinite (Pd31Sb12) occur as solid phases. In addition, solid phases with compositions of Pd20Sb7 and Pd5Sb2 are present. The extents of the Pd substitution for Pt in stumpflite and geversite were measured to be 18 and 7.2 atom (at.) %, respectively. Mertieite II (Pd8Sb3) and stibiopalladinite (Pd31Sb12,) show almost identical extent of the Pt-Pd substitution (22 at.%). The Pt substitutions for Pd in synthetic phases of Pd20Sb7 and Pd5Sb2 range up to 27 and 19.6 at.%, respectively. Pt and Pd form a complete solid solution and their solid solutions with Sb range from 7.5 at.% along the Pt-Sb binary join to 16.5 at.% along the Pd-Sb binary join.