Ag, Cu, Hg, Pt, Sb and Te substitutions in the synthetic analogue of palladseite, Pd17Se15: an experimental mineralogical study
Abstrakt
The solubility of Ag, Cu, Hg, Pt, Sb and Te in the synthetic analogue of palladseite was experimentally studied at 350 degrees C. To document the impact of these elements on the palladseite crystal structure, Rietveld refinement analysis of experimental products was performed.
The synthetic Pd17Se15 dissolves at 400 degrees C 3.6, 6.4, 8.8, 9.7, 6.1 wt. % of Cu, Ag, Hg, Pt and Te, respectively. The solubility of Sb in synthetic Pd(17)Se(15) is less than 0.03 wt. %.
Three different types of incorporation of the above-mentioned elements to the palladseite structure have been observed. Ag, Cu and lig occupy a position 3d of the Pm-3m space group, which was empty in the unsubstituted Pd(17)Se(15).
Consequently, Pd occupancy of adjacent [Pd(4)Se6] octahedron is reduced to 0.46 and 0.51 for Cu and Ag-bearing palladseite, respectively. Incorporation of Hg to the palladseite structure causes vacancy of this Pd(4) position.
Pt partially substitutes Pd at the Pd(2) position (6f), forming Pd(0.41)/Pt(0.59) mix site showing square-planar coordination by Se atoms. Te atoms substitute for Se.
The refined unit-cell parameter increased from the initial value of a = 10.6074(1) Å for Pd(17)Se(15) to 10.6680(1) Å for Te-bearing palladseite. Incorporation of Cu, Ag and Hg to the palladseite causes significant changes of its powder X-ray diffraction pattern and hence can be detected by PXRD.