Naslov
Investigation of Ba8Au5.25Ge40.3□0.45 under hydrostatic pressure

Autori
Popčević, Petar ; Barišić, Neven ; Krellner, Kornelius ; Buehler-Paschen, Silke ; Grin, Yuri ; Smontara, Ana

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
New thermoelectric materials: Thermoelectrics 2013 / - , 2013

Skup
New thermoelectric materials: Thermoelectrics 2013

Mjesto i datum
Split, Hrvatska, 28.09.2013. - 01.10.2013

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
clathrates; hydrostatic pressure; transport properties

Sažetak
Due to relatively large figure of merit (ZT can reach values higher than 1), its chemical and thermal stability at high temperatures Clathrates are very promising thermoelectric materials. Since Bacontaining clathrates are considered to be prospective thermoelectrics, in the current spot of interest are ternary type-I clathrates in Ba-Au-Ge and Ba-Ag-Ge systems. The main research activity was focusing mainly on solubility range, phase equilibria and some transport properties.[1-4] It seems that depending on Au (Ag) content dominant electrical carriers can be of p or n type while the temperature dependence revels either metallic or semiconducting behaviour. Hydrostatic pressure is powerful tool for probing electronic structure of material. Through changing interatomic distances it directly influences band structure increasing overlapping integrals and electronic velocities. In particular it is useful to use it in to fine tune the system in a proximity of a phase transition and by that probe the stability of the system and help elucidate interactions driving the transition.[5] Here we present first measurements of transport properties (electrical resistivity and thermoelectric power) behaviour under hydrostatic pressure measured from low (1.5K) up to room temperature of the monocrystal clathrate type I solid solution Ba8AuxGe46-x-y□y (x=5.25, y=0.45). Compared to known studies [3, 4] of Ba8AuxGe46-x-y□y system our composition shows the largest thermopower amounting 395 μΩcm at room temperature. Electrical resistivity at room-temperature was found to be 47 mΩcm, also the largest one. Interestingly, electrical resistivity rises linearly with pressure at rate 2.4 mΩcm/GPa while thermopower is pressure independent up to 2 GPa. For this particular composition Fermi level is expected to be located in the narrow energy gap close to the top of the valence band. Increase of electrical resistivity with pressure is probably due to widening of the energy gap and/or shift of the Fermi energy to higher values. Deviation of semiconducting like behaviour of electrical resistivity at low temperatures (T<10K) could be connected to presence of small amount of density of states within the gap due to impurities and vacancies.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

Napomena
The paper was presented as a poster by Petar Popčević. This work was done within the activities of the European Integrated Center for the Development of New Metallic Alloys and Compounds - C-MAC.

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