Influence of chemical composition on the X-ray photoemission, thermopower, specific heat, and magnetic properties of CeNi2(Si1-yGey)(2)

We report our studies of the intermediate compositions between CeNi2Si2 and CeNi2Ge2, i.e., the alloys CeNi2(Si1-yGey)2 by means of the thermopower, electrical resistivity, specific heat, magnetic susceptibility, and X-ray photoemission measurements. CeNi2Si2 is a fluctuating valence system and CeNi2Ge2 is known to show the heavy fermion behaviour. The change of the temperature dependence of the resistivity towards the typical metallic behaviour occurs below y ~ 0.25. The transition between CeNi2Si2 and CeNi2Ge2 is discussed in the frames of competition between the crystal electric field and Kondo interactions. It is found that valence stabilisation occurs for Ge content y > 0.25. The hybridization energy Δ determined from the XPS Ce 3d spectrum reflects well the behaviour of the parameter Eex obtained from the analysis of the magnetic susceptibility by the interconfiguration fluctuation model. It has been also shown that thermopower data can be successfully described employing the single ion model for 0.6 < y < 1.0 and two-band model including the crystal electric field splitting for y ≤ 0.25

Enhanced Thermoelectric Power Factors in the Ce(Ni_{1-x}Cu_{x})₂Si₂ and CeNi₂(Si_{1-y}Ge_{y})₂ Alloys

In the presence of hybridization of the f states with the conduction electrons Ce-based compounds can show large peaks in the temperature dependence of the Seebeck coefficient, which makes them interesting materials for applications. The Seebeck coefficient and electrical resistivity of the bulk, arc-melted, single phase samples of Ce(Ni_{1-x}Cu_{x})₂Si₂ and CeNi₂(Si_{1-y}Ge_{y})₂ alloys were measured over the temperature range of 2 K to 300 K. All the samples exhibited a positive Seebeck coefficient, which reaches up to ım50μV/K at 150 K and it can be shifted up to 300 K by appropriate doping. The thermoelectric power factor, PF = S²/ρ, reached a maximum of 1.4×10¯³ Wm¯¹K¯² at 290 K and 1.1×10¯³ Wm¯¹K¯² at 110 K for x=0.25 and y=0.75, respectively. For selected representatives of the studied series thermoelectric properties have been measured up to 1000 K

Transfer factor as technologies socio-economic development of Western Ukraine

We consider some aspects of technology transfer between Ukraine and Poland, which is a factor in enhancing regional development. Deemed appropriate to the formation of the Polish-Ukrainian space technology cluster, as an effective mechanism for technology transfer interstate

European integration of Ukrainian research institutions: prospects of using of EU funds

The goal of this article is to present perspective of using European funds in Ukrainian research institutions. Effective cooperation of Ukraine with the European Union in the direction of research will foster the intensification of political and economic relations, the use of new mechanisms to stimulate research and development of public awareness of the importance of science for the development of society. Coordination of joint research interest is added by the integration of Ukraine (by creating a single space science and technology) with the European Union. Of particular importance is the fact that the mutual benefits of the research programs

Thermal transport in the intermetallic compound CeNi 4Cr

Electrical resistivity, thermopower (TEP), thermal conductivity and the thermoelectric figure of merit are studied for the CeNi4Cr compound, which has been previously suggested to be a fluctuating valence system with a tendency to the increase of the effective mass at low temperatures. The analysis of the thermoelectric properties confirms such a possibility and provides characteristic parameters like the Debye temperature, Fermi energy and the position of the f band. Both the thermopower and the magnetic part of the electrical resistivity could be analyzed within a similar model assuming a narrow f-band of the Lorentzian form near the Fermi energy. The thermal conductivity shows that the phonon contribution exceeds the electronic one below 220 K

Ferromagnetic CeSi1.2Ga0.8 alloy: Study on magnetocaloric and thermoelectric properties

We present the magnetic, specific heat, electrical resistivity, and thermoelectric power measurements for the intermetallic compound CeSi1.2Ga0.8. This composition belongs to the series CeSi2-xGax, which exhibits diverse magnetic orderings and different crystallographic structures depending on the substitution level x. It has been previously suggested that for 0.0 < x < 1.3 the compounds crystallize in the alpha-ThSi2 type structure and for 0.7 < x < 1.3 they order ferromagnetically below 14 K. Our complementary studies for x = 0.8 reveal that it is a complex system due to the Kondo scattering competing with the RKKY interactions. The transition from the paramagnetic to the ferromagnetic state takes place at T-C = 12.5(1) K. Moreover, the Seebeck coefficient and electrical resistivity show not only an anomaly related to the magnetic transition, but also a broad maximum at-90 K related to the crystal field effect. The case of x = 0.8 is of special interest as it is at the crossing of the characteristic temperatures, i.e. T-ord (magnetic ordering temperature)similar to & nbsp; T-K (Kondo temperature) similar to 10 K. Additionally, ab initio electronic structure calculations were performed allowing us to determine phase stability, (revealing two stable phases -alpha-GdSi2-type and alpha-ThSi2-type structures) as well as spin and orbital moment decomposition on Ce-states for both considered structures.Web of Science547art. no. 16883