Band Electronic Structure Study of Some Doped and Undoped γ-Ln2S3(Ln=La, Ce, Pr, and Nd) Rare Earth Sulfides through LMTO-TB Calculations

Zhukov, V. P.; Mauricot, Robert; Gressier, P.; Evain, Michel

doi:10.1006/jssc.1996.7185

Cited by 24 publications

(22 citation statements)

References 28 publications

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“…We find that the Fermi level is still in the conduction band in the case of La 11 X 16 , whereas it is inside the conduction band in the case of La 5 X 8 . Our results are in good agreement with some previous calculations in the literature [40,42,43] and confirm the validity of the use of the RBA for La 3-y X 4 compounds in order to study their electronic and thermoelectric properties. Therefore, one can see the lanthanum vacancies as electron acceptors, as it has been observed experimentally.…”

Section: Figuresupporting

confidence: 92%

“…7, we report how the power factor (PF) is changing with the position of the chemical potential at 300 K and 1273 K. This PF has been determined with the assumption that the relaxation time τ is equal to 2*10 -15 s. This value has been chosen since it gives the best agreement between the available experimental data of the electrical conductivity for La 3 Te 4 and La 3 S 4 and the calculated electrical conductivities as a function of charge carrier concentration (not shown). This procedure to determine the relaxation time has been previously used in the literature as well [92,93].For comparison, we also show the evolution of the density of states with the chemical potential at 0 K. As discussed above and by others [40,42,43], the RBA works very well for these compounds and in the following we will discuss how the thermoelectric properties change with the charge carrier concentration within this approximation.…”

Section: Thermoelectric Propertiesmentioning

confidence: 76%

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Physical properties of the thermoelectric cubic lanthanum chalcogenides La3−yX4(X= S, Se, Te) from first principles

2013

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We report ab-initio calculations of the stability, lattice dynamics, electronic and thermoelectric properties of cubic La 3-y X 4 (X=S,Se,Te) materials in view of analyzing their potential for thermoelectric applications. The lanthanum motions are strongly coupled to the tellurium motions in the telluride, whereas the motions of both types of atoms are decoupled in the sulfides. Nevertheless, this has no impact on their thermal properties because experimentally all compounds have low thermal conductivity. We believe that this is due to Umklapp scattering of the acoustical modes, notably by the low energy optical modes at about 7-8 meV found in all three chalcogenides, as in cage compounds such as skutterudites or clathrates, even though there are no cages in the cubic Th 3 P 4 structure. We find that the energy bandgap increases from the telluride to the sulfide in good agreement with the experiments. However, due to their similar band structure, we find that all three compounds have almost identical thermoelectric properties. Our results agree qualitatively with the experiments, especially in the case of the telluride for which a great amount of data exists. All our results indicate that the sulfides have strong potential for thermoelectricity and could replace the tellurides if the charge carrier concentration is optimized. Finally, we predict also a larger maximum ZT for the p-type doped materials than for the n-type doped ones, even though compounds with p-doping have still to be synthesized.Thus our results indicate the possibility to make high temperature performing thermo-generators based only on La 3 X 4 compounds.PACS numbers: 63.20.dk,71.15.Nc, 72.15.Jf, 72.20.Pa 1

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Section: Figuresupporting

confidence: 92%

Section: Thermoelectric Propertiesmentioning

confidence: 76%

Physical properties of the thermoelectric cubic lanthanum chalcogenides La3−yX4(X= S, Se, Te) from first principles

2013

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“…The fundamental optical band gaps in the -¸n S compounds originate from the separation between the 3p(S) valence band at the M point and the 5d(¸n) conduction band at the point of the Brillouin zone (13,31). The energy dependence of the imaginary part of the dielectric function ( " #i ) provides information on direct interband transitions at higher energies than the indirect fundamental absorption band (13,31).…”

Section: Resultsmentioning

confidence: 99%

“…The energy dependence of the imaginary part of the dielectric function ( " #i ) provides information on direct interband transitions at higher energies than the indirect fundamental absorption band (13,31). Witz et al (32) deduced that in -Gd S the values of the indirect gap and of the lowest direct interband transition are equal to 2.75 and 3.4 eV, respectively.…”

Section: Resultsmentioning

confidence: 99%

Stability and Optical Properties of γ-Gd2S3 at High Pressures

Grzechnik

1999

Journal of Solid State Chemistry

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“…The result is that these DFT calculations fail to reproduce, e.g. the non-metallic ground state of Ce 2 S 3 [3,4] and overestimate the mass density of crystal structures of other cerium compounds [5,6,7]. Hence, approaches beyond conventional DFT methods are required to describe Ce 2 S 3 realistically from first principles.…”

Section: Introductionmentioning

confidence: 99%