ICT2014 Abstracts

We experimentally investigated the reduction of lattice thermal conductivity (K_L) in the temperature range (30-800K) of n-type  Si₈₀Ge₂₀P₂ alloys with the incorporation of Yttria Stabilized Zirconia (YSZ) nanoparticles (20 to 40 nm diameter) into the Si-Ge matrix. These samples were synthesized using the Spark Plasma Sintering (SPS) technique, which yielded densities > 95% of the theoretical density. The thermal conductivities at low and high temperatures were measured by steady state and laser flash techniques respectively. At T= 200K, about 40% and 50% reduction in the lattice thermal conductivity occurs by adding 5% and 10% by volume of YSZ respectively to the Si₈₀Ge₂₀P₂ alloys.

A phenomenological model developed by Callaway is used to corroborate temperature dependence and reduction of K_L at low and high temperatures of both Si₈₀Ge₂₀P₂ and  Si₈₀Ge₂₀P_{2 + YSZ} alloys. It is assumed that K_L can be represented by phonon relaxation times arising from alloy disorder, Umklapp, and boundary scattering processes. In addition, contribution from the relaxation time for phonon scattering by YSZ nanoparticles included in the Si₈₀Ge₂₀P₂ model, accounts for the observed reduction in K_L. The theoretical calculations are in reasonably good agreement with the experimental results for both Si₈₀Ge₂₀P₂ and Si₈₀Ge₂₀P_{2 + YSZ} alloys.