Enhanced electronic and thermoelectric properties of p-type doped filled skutterudites RFe4Sb12 (R = Pr, Nd)
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A semimetallic type of electronic profile has been predicted for RFe4Sb12 (R = Pr, Nd) from a first-principles investigation, where the presence of a small energy bandgap above the Fermi energy level (EF) is a key feature. The EF lies at the top of the valence band and it is crossed by a single band more than twice, which improves the band concentration and electronic specific heat as reflected by the high Seebeck coefficient. The doping of a heavy lanthanide atom at the center of the cage formed by pnictogen atoms has a significant effect on the electronic structure that enhances the Seebeck coefficient and the thermoelectric power factor. The heavy atom at the center also dampens the lattice vibration and lowers the lattice thermal conductivity. The Nd-doped system shows an enhanced Seebeck coefficient with the highest power factor among the sample alloys. Moreover, due to significant reduction in the lattice thermal conductivity from 2.46 W/m K to 0.54 W/m K, a maximum ZT value of ∼1.11 at 800 K has been observed for an Nd-doped system. The covalent nature of PrFe4Sb12, Pr-doped NdFe4Sb12, and Nd-doped PrFe4Sb12 and the ionic nature of NdFe4Sb12 have been confirmed, where Pr-doped NdFe4Sb12 is the stiffest and a highly rigid material with strong bonding forces among the constituent atoms. The results presented in this manuscript open the possibilities for further exploration of center atom-doped filled skutterudites with improved Seebeck coefficient and reduced lattice thermal conductivity, which are promising materials for thermoelectric applicationsKeywords:
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The interactions between a series of lanthanide cations (Ln3+) and a methyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril (SHMeQ[6]) in the presence of [CdCl4]2 − as a structure-directing agent in aqueous HCl solutions (6.0 mol·L − 1) have been investigated. The formation of ionic radius-dependent complexes, the crystal structures of six of which have been obtained, shows the recognition ability of SHMeQ[6] towards lanthanide cations. For example, SHMeQ[6] forms molecular capsule-like complexes with the two lightest lanthanide cations, La3+ and Ce3+; molecular pairs with Nd3+, Sm3+, Eu3+ and Gd3+, and no solid crystals are formed with the heavier lanthanides.
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Abstract Phthalocyanine complexes of yttrium(III) and lanthanoid(III) ions, Pc3Ln2 (Pc = phthalocyanine anion, Ln = lanthanoid(III) cation) were prepared and characterized. A Q band undergoes a blue shift with a decrease in ionic radius of the lanthanoid(III) ions, while an X band undergoes a red shift.
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Lanthanide contraction
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The various influemce factors to the physicochemical properties of lanthanide are studied in this paper and the physicochemical properties of nine kinds of lanthanide are associated too using lanthanide foundation state value L,electronegativity 4f,electronic arrangement periodic factors q and ionic radius as the parameters and using the BP neural network based on L-M optimization algorithm.The obtained results are satisfactory and this method is better than the ordinary linear regress method and suitable to the study on completed quantitative structure-property relationship.
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The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.
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