Study On The Phase Diagrams Of Cr-Pb-Sb, Er-Fe-Sb System And On The Cystal Structure Of New Compounds

Phase relations in the Cr-Pb-Sb ternary system at 500K and Er-Fe-Sb ternary system at 773K have been investigated in this work, with having destined the crystallographic structure of FeR(R=Ho,Er,Tb)₆Sb₂. The main contents of them were related as followed:1. The isothermal section of Cr-Pb-Sb ternary system at 500KPhase relations in the Cr-Pb-Sb ternary system at 500K have been investigated by means of X-ray diffraction technique and optical microscope method. There are three three-phase regions, seven two-phase regions and five single-phase regions in this isothermal section. The maximum solid solubility of Sb in Pb at 500K is about 3.3 at.% determined by the varying of lattice parameters and the method of vanishment of phase.2. The isothermal section of Er-Fe-Sb ternary system at 773KPhase relations in the Er-Fe-Sb ternary system at 773K have beeninvestigated by means of powder X-ray diffraction technique, differential thermal analysis. Eight binary compounds have been confirmed through our study: A(Er₂Fe₁7), B(Er₆Fe₂3), C(ErFe₃), D(ErFe₂), E(Er₅Sb₃), F(ErSb), G(FeSb₂), H(FeSb). And Er₄Sb₃ and ErSb₂ have not been found at this isothermal section. At the meantime, we found the FeSb has a solid soluble region. The solid solubility of Fe₁+x Sb which was determined by the varying of lattice parameters is about 2.2 at.%. We found a new ternary compound I(FeEr₆Sb₂). According to the results of experiment, we constructed the phase diagram of Er-Fe-Sb ternary system at 773K. It consists of 12 single-phase regions, 22 two-phase regions and 11 three-phase regions.3. Crystal structure of the compound FeR(R=Ho,Er,Tb)₆Sb₂The crystal structure of the new compound FeR(R=Ho,Er,Tb)₆Sb₂ have been studied by powder X-ray diffraction technique and refined by Rietveld profile fitting method. All the three compounds crystallize in the hexagonal Fe₂P-type structure (space group:P-62M, No.189). The lattice parameters of FeHo₆Sb₂ is a=8.1403(3)A, c=4.1346(2)A, z=l, D_calc. =9.019g/cm³, the Rietveld refinement result was R_p=7.91% and R_wp=10.01%. The lattice parameters of FeEr₆Sb₂ is a=8.0914(3)A, c=4.1245(2)A, z=1, D_calc=9.234g/cm³, the Rietveld refinement result was R_p=9.49% and R_wp=11.92%. The lattice parameters of FeTb₆Sb₂ is a=8.1942(5)A, c=4.1758(3)A , z=1 , D_calc=8.564g/cm³. The Rietveldrefinement result was R_p=8.17% and R_wp=10.75%.