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First-principles study of elastic, electronic, optical and thermoelectric properties of newly synthesized K2Cu2GeS4 chalcogenide
摘要： In this article, we report the elastic, electronic, optical and thermoelectric properties of recently synthesized K2Cu2GeS4 chalcogenide. The structural parameters are found to be in good agreement with experimental results. The calculated single crystal elastic constants (Cij) show that K2Cu2GeS4 is mechanically stable. The investigated electronic band structures reveal semiconducting characteristics and are consistent with experiment. Important optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function are calculated and discussed in detail. Optical conductivity is found to be in good qualitative agreement with the results of band structure calculations. The Seebeck coefficients for TB-mBJ potential within the studied temperature range vary from ~450 to ~200 m V/K. The anisotropic electrical conductivity and electronic thermal conductivity are observed in the layered structured K2Cu2GeS4. The power factor and electronic thermal conductivity at 800K along xx-axis using TB-mBJ potential are found to be ~6 m Wcm-1K-2 and 0.578 Wm-1K-1, respectively and the corresponding thermoelectric figure of merit is 0.81. The obtained results predict that K2Cu2GeS4 is a promising material in thermoelectric device applications.
关键词： electronic properties,optical properties,elastic properties,thermoelectric properties,K2Cu2GeS4
更新于2025-09-09 09:28:46
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Temperature and pressure induced Raman studies of C 60 oxide
摘要： We present temperature, laser power, and pressure dependent Raman spectral analysis of C60 oxide (C60O) thin films prepared by the photolysis method. The first order temperature, laser power, and pressure coefficients of the Raman frequencies are evaluated and are utilized for evaluating the thermal conductivity of C60O. Its thermal conductivity is found to be 0.7 W m-1 K-1 which is marginally higher than that of bulk C60. Raman frequencies corresponding to C–O and C–C bonds blue-shift with a decrease in temperature which is attributed to the thermal contraction of C60O molecules. The density functional measurements have been performed to optimize C60O structure. The contraction in the C–O bond length has been corroborated with the experimental Raman shifts at different temperatures and is used to evaluate the linear expansion coefficient of C60O. Pressure induced compression and polymerization of C60O clusters are also illustrated. This study highlights the interplay between thermal and mechanical transformations in the C60O cluster which may regulate its thermoelectric properties by tuning the intermolecular interactions.
关键词： pressure dependence,thermoelectric properties,Raman spectroscopy,thermal conductivity,C60 oxide,laser power dependence,temperature dependence
更新于2025-09-09 09:28:46
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Direct probing of cross-plane thermal properties of ALD Al <sub/>2</sub> O <sub/>3</sub> /ZnO superlattice films with improved figure of merit and their cross-plane thermoelectric generating performance
摘要： There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, has not been performed from these semiconducting superlattice films, because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present technique using a structure of sandwiched superlattice films between two embedded heaters as heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al2O3/ZnO superlattice films, prepared by atomic layer deposition (ALD) method. Used in combination with the promising cross-plane four-point-probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al2O3/ZnO superlattice films in the temperature range from 80 to 500 K. Our experimental methodology and the obtaining results represent a significant advancement in the understating of phonon and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.
关键词： Thermal conductivity,Cross-plane thermoelectric properties,Seebeck coefficient,Phonon transport,Superlattice films,3-omega measurement,Phonon scattering
更新于2025-09-09 09:28:46