The Seebeck coefficient and electrical resistivity have been measured for the La3−x Mx S4 alloys with the Th3 P4 -type structure for M=Sm, Eu, Yb, and x=0.1 to 0.9 in order to determine their potential as high-temperature thermoelectric energy conversion materials. An analysis of the lattice parameters of these alloys suggests that Sm has a valence of 2.2 over the entire composition range. Furthermore, the variation of the Seebeck coefficient and electrical resistivity as a function of electron concentration is different for the Sm-doped alloys than for the Eu- and Yb-doped alloys, which are all different from that of the pure binary LaSy alloys. A maximum in the electrical power factor at 1000 °C is found to occur at x ≂ 0.3, but when a reasonable estimate is made of the thermal conductivity the maximum in the figure-of-merit at 1000 °C shifts to larger x values (∼0.7) in all alloy systems. The long term stability of the Sm and Eu ternaries is also reported.
The phase relationships and the important structural, electrical and thermal properties of the R3X4-R2X3 (where R = lanthanides and X = S, Se and Te) phases having the Th3P4 -type structure are reviewed. The room temperature electrical resistivity and Seebeck coefficient of these materials are independent of R and only slightly dependent on X, but critically dependent on the X:R ratio. The long term stability of these phases is also reviewed. Although these materials have good thermoelectric properties there are some problems which need to be solved before these phases can be utilized in thermoelectric devices. These problems include long term stability, higher than desirable thermal conductivities, and low electron mobilities.
A new source localization algorithm with no requirement of onetoone source correspondence between biplane radiographs Med.A onetoone mapping between oneparticle densities and some nparticle ensembles Self-consistent electronic structure calculations have been performed on two compositions of scandium sulfide ScS and SC 3 S 4 • The results of the calculation ofScS are similar to those obtained for other transition metal chalcogenides and are in excellent agreement with heat capacity and reflectance measurements as well as UPS experiments. The calculation of the defect structure indicates the creation of sulfur p nonbonding states in metal-deficient ScS. The valency of the metal ions remains unchanged upon the creation of vacancies. technique on large clusters of atoms. 12.13 The results of this 1964
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