0000000001009927
AUTHOR
Ville Härkönen
Computational and theoretical studies on lattice thermal conductivity and thermal properties of silicon clathrates
The lattice thermal conductivity is usually an intrinsic property in the study of thermoelectricity. In particular, relatively low lattice thermal conductivity is usually a desired feature when higher thermoelectric efficiency is pursued. The mechanisms which lower the lattice thermal conductivity are not known in sufficient detail and deeper understanding about the phenomena is needed and if such understanding is achieved it can be used to design more efficient thermoelectric materials. In this thesis, the lattice thermal conductivity and other thermal properties of several silicon clathrates, which are known to be promising candidates for the thermoelectric applications, are studied by theoreti…
Ab initio computational study on the lattice thermal conductivity of Zintl clathrates [Si19P4]Cl4 and Na4[Al4Si19]
The lattice thermal conductivity of silicon clathrate framework Si23 and two Zintl clathrates, [Si19P4]Cl4 and Na4[Al4Si19], is investigated by using an iterative solution of the linearized Boltzmann transport equation in conjunction with ab initio lattice dynamical techniques. At 300 K, the lattice thermal conductivities for Si23, [Si19P4]Cl4, and Na4[Al4Si19] were found to be 43 W/(m K), 25 W/(m K), and 2 W/(m K), respectively. In the case of Na4[Al4Si19], the order-of-magnitude reduction in the lattice thermal conductivity was found to be mostly due to relaxation times and group velocities differing from Si23 and [Si19P4]Cl4. The difference in the relaxation times and group velocities ar…