Transition metal oxides – Thermoelectric properties

A survey of experimental findings for Ce-Cu- and Yb-Cu-based compounds is given. Most of these compounds exhibit unusual physical properties as a consequence of various competing mechanisms such as a magnetic interaction of the Ruderman-Kittel-Kasuya-Yoshida type, Kondo interaction and crystal-field splitting. The ground-state properties are then dominated by whichever process surpasses the others. A successful description of the observed behaviour is possible in terms of the Coqblin-Schrieffer model, which is based on the Anderson Hamiltonian which is more general than the Kondo Hamiltonian.

Anomalous properties of Ce-Cu- and Yb-Cu-based compounds

Measurement of mass attenuation coefficients and effective atomic numbers for MgB2 superconductor using X-ray energies

An effective method of preparation of bismuth nanopowders by thermal decomposition of bismuth dodecyl-mercaptide Bi(SC12H25)3 and preliminary results on their thermoelectric properties are reported. The thermolysis process leads to Bi nanoparticles due to the efficient capping agent effect of the dodecyl-disulfide by-product, which strongly bonds the surface of the Bi clusters, preventing their aggregation and significantly reducing their growth rate. The structure and morphology of the thermolysis products were investigated by differential scanning calorimetry, thermogravimetry, X-ray diffractometry, 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. It has been shown that the prepared Bi nanopowder consists of spherical shape nanoparticles, with the average diameter depending on the thermolysis temperature. The first results on the thermoelectric characterization of the prepared Bi nanopowders reveal a peculiar behavior characterized by a semimetal–semiconductor transition, and a significant increase in the Seebeck coefficient when compared to bulk Bi in the case of the lowest grain size (170 nm).

Synthesis and thermoelectric characterisation of bismuth nanoparticles

The magnetic properties of NdxFe1−x (0.04≤x≤0.09) amorphous thin films were studied in the temperature range 1.5–300 K at H=7 T. It was found that in these films the asperomagnetic and speromagnetic structures existed. The effective magnetic moment per Nd atom varied from 1.2 μB to 1.06 μB, and the distribution angle 2ψ0 of neodymium moment from 210° to 222° corresponding to x=0.04 to 0.90. The magnetic moment of iron atom also varied from 2.1 μB to 1.2 μB.

J. Sakurai

Papers

Thermoelectric power of RAl2