| Summary: | 碩士 === 國立交通大學 === 應用化學系所 === 93 === In this report, five new chalcogenides, MPb4In8Se17 ( M=Mn, Fe ) and M0.5Pb4In8.5S17 ( M=Cu, Ag, Au ) were synthesized at 1023K and 1123K by solid-state reactions. These compounds crystallized in the space group P21/m, monoclinic system. The crystal structure features the combinations of CdI2-type layer of [InX2] and NaCl [100]-type layer of [(MxIn1-x)PbInX3] units along c-axis. For selenide phases, Mn and Fe atoms prefer to occupy on M12 and M13 sites. On the other hand, for the sulfide phases, the late transition metals ( Cu, Ag, Au ) favor to occupy on M10 and M11 sites. The results of LMTO band calculations indicate that Mn d and Fe d orbitals dominate the electronic states near the Fermi level and the interactions to surrounding Se atoms are essentially weak antibonding, which suggest bad mobility of electrons from Mn d and Fe d orbitals. These compounds show semiconducting behavior and possess large resistance in the electrical conductivity and thermopower measurements. UV absorption experiments for the sulfide phases suggest the band gap are close to 1.4eV. The magnetic susceptibility measurements for the Mn-phase show typical paramagnetic behavior of spin only Mn2+ ( t2g3eg2, S=5/2 ). However, the molar susceptibility of Fe-phase indicates a phase transition occurred at 125K.
|
|---|
