Raman spectra and structure of γ- Ln2S3 vacancy crystals

Kolesov, B. A.; Kamarzin, A.A.; Соколов, В. В.

doi:10.1007/bf02762735

Cited by 8 publications

(6 citation statements)

References 7 publications

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“…We note that experimentally there is an uncertainty for the position of the other T 2 modes, excepted for the mode at about 22-23 meV that was found in all experimental reports [76][77][78]. In this region of the spectrum, we note that Koselov et al also suggest the presence of a second T 2 mode at about 20 meV [77]. Our calculations seem to confirm this assignment as we have found the presence of two T 2 modes at 19.2 and 22.9 meV.…”

Section: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 68%

“…Unfortunately, the determination of the mode symmetry has been performed with polarized Raman experiment only in the case of the cubic γ-La 2 S 3 , i. e. for the compound with the vacancies [77]. This will make more difficult a quantitative comparison with our calculations due to the changes induced by the defects in the vibrational spectrum, as discussed above.…”

Section: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 99%

“…Now we compare our lattice dynamics calculations with the few available experimental data [41,[74][75][76][77][78][79].In Table 3, we report the vibrational modes calculated at Γ point for all three compounds that can be compared with the experimental data from Raman and infrared spectroscopy available in the literature that we have reported in Table 4 [74][75][76][77][78]. In the case of La 3 Te 4 , the phonon density of states has been recently measured by Delaire et al [41] who found a broad maximum at about 8 meV, followed by a dip at about 10-11 meV, a shoulder at about 12 meV and another maximum at about 16 meV, the phonon DOS becoming zero at about 17-18 meV.…”

Section: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 99%

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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: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 68%

Section: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 99%

Section: Lattice Dynamics and Thermal Propertiesmentioning

confidence: 99%

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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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“…In order to determine the composition of the system, Raman spectra were obtained for different samples and the result is depicted in Figure b. The prominent Raman peaks featuring pristine SnS 2 , CeO 2 , and Ce 2 S 3 appear at 313 cm −1 (A 1g mode), 453 cm −1 (F 2g mode), and 225 cm −1 (E g mode), respectively. Notably, the variety in intensity of the peaks at 225 and 453 cm −1 for T6, T15, and T24 can be related to the extent of growth for CeO 2 on the surface of Ce 2 S 3 .…”

Section: Resultsmentioning

confidence: 99%

Efficient Photocatalytic Hydrogen Evolution via Band Alignment Tailoring: Controllable Transition from Type‐I to Type‐II

Cheng

Wang

Shifa

et al. 2017

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Considering the sizable band gap and wide spectrum response of tin disulfide (SnS ), ultrathin SnS nanosheets are utilized as solar-driven photocatalyst for water splitting. Designing a heterostructure based on SnS is believed to boost their catalytic performance. Unfortunately, it has been quite challenging to explore a material with suitable band alignment using SnS nanomaterials for photocatalytic hydrogen generation. Herein, a new strategy is used to systematically tailor the band alignment in SnS based heterostructure to realize efficient H production under sunlight. A Type-I to Type-II band alignment transition is demonstrated via introducing an interlayer of Ce S , a potential photocatalyst for H evolution, between SnS and CeO . Subsequently, this heterostructure demonstrates tunability in light absorption, charge transfer kinetics, and material stability. The optimized heterostructure (SnS -Ce S -CeO ) exhibits an incredibly strong light absorption ranging from deep UV to infrared light. Significantly, it also shows superior hydrogen generation with the rate of 240 µmol g h under the illumination of simulated sunlight with a very good stability.

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“…A highly symmetric ordering of the vacancies is likely in well-annealed γ-phases whereas rapidly quenched samples might have a random distribution of vacancies [33]. Vacancies in the sulfur sublattice are rather unlikely [36]. [34].…”

Section: Crystal Structuresmentioning

confidence: 99%