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Journal of Applied Mathematics and Statistical Applications | Volume: 1

August 23-24, 2018 | London, UK

Applied Physics

International Conference on

Low-temperature thermal properties of type-1 thermoelectric clathrates

Kirill Pilipenko

Petrovsky Bryansk State University, Russia

hermoelectric type-1 clathrates are a special class

of substances whose crystal structure features lead

to low values of their thermal conductivity and high

electrical conductivity (“phonon glass electron crystal”).

This contradictory combination of properties is achieved

due to quasi-independent vibrations of guest atoms in

the cavities of the host matrix and the presence of free

electrons from the host atoms. The specific heat (2-300 K)

and lattice parameters (5-300 K) of clathrates-1 of different

compositions were studied. It was established that the

phonon spectra of clathrates are satisfactorily approximated

by two Einstein functions accounting for vibrations of guest

atoms in cavities of two different types and one Debye

function describing vibrations of matrix-host. Second, we

show that the possibility of the guest atoms to occupy

spatially close but energetically non-equivalent states

in the host cavities leads to the formation of two-level

systems and, consequently, to a specific low-temperature

contribution to the thermal characteristics of clathrates-1,

which can be described by the Schottky function. Finally, we

have found that the presence of vacancies in the host matrix

and the disorder of the arrangement of constituent atoms of

different types lead to a glass-like contribution to the heat

capacity and thermal expansion of the clathrate-1 at the

lowest experimental temperatures; this contribution varies

linearly with the temperature.

Speaker Biography

Kirill Pilipenko is graduate student from Petrovsky Bryansk State University, Russia.

He has 2 publications, and his publication H-index is 1.