Thermoelectric performance of silicon with oxide nanoinclusions

Abstract

Silicon nanoparticles produced via a plasma-based technique have been sintered into bulk nanostructured samples. These samples have micron-sized crystalline domains and contain well-dispersed oxide nanoinclusions. We have compared the thermoelectric performance of such structure to that of a control sample produced by sintering ball-milled silicon powders. The control sample has lower precipitate density and is composed of nanograins. Despite the stark difference in nanostructure, both samples have comparable thermal conductivity, and the sample with nanoinclusions has higher power factor and ZT. This result confirms that grain size engineering is not the only promising route to achieving improved thermoelectric performance. IMPACT STATEMENTBy controlling the feedstock powder processing technique, it is possible to obtain well-dispersed nanoinclusions in sintered bulk samples. These are as effective at reducing thermal transport properties as grain boundaries.

Enhanced Thermoelectric Performance in n-Type SrTiO3/SiGe Composite

“…These variations became smaller with increasing amounts of added SrTiO 3 , resulting in a larger μ value in the composite sample at high temperature than that for the single-phase SiGe. Although the oxide nanoinclusions in SiGe have been reported to act as a phosphorus reservoir, no such behavior was observed in our data. In contrast, the addition of SrTiO 3 suppresses the rise of n at high temperatures, indicating that the oxide phase traps the precipitated phosphorus (as observed in Figure ) and prevents the formation of a solid solution of phosphorus in Si at high temperature.…”

“…36,37 Because the carrier concentration decreased with increasing SrTiO 3 content (Figure 5c), when the SrTiO 3 content increased to ≥5 wt %, σ significantly decreased, indicating that the contribution of n to σ becomes more significant than that of the mobility. The rise in n at high temperature can be attributed to the increased solubility of phosphorus in silicon, 33,38 which induced an additional reduction of μ (as discussed above) coming from ionized impurity scattering. These variations became smaller with increasing amounts of added SrTiO 3 , resulting in a larger μ value in the composite sample at high temperature than that for the single-phase SiGe.…”

“…Some precipitation of the P-rich and the oxide phases were observed in the SEM-EDS mapping, as shown in Figure and Figure S2. In contrast with the single-phase SiGe, the P-rich phase precipitated near some oxide in the composite samples, whereas P usually precipitated at the grain boundary in the single-phase SiGe samples. , TEM analysis was carried out to confirm the composition of the oxide phase. The low-resolution TEM image (Figure a) showed that there were many spherical inclusions randomly distributed at the grain boundary of the SiGe matrix, and a portion of them combined with the irregular white particles.…”

Insights into the Classification of Nanoinclusions of Composites for Thermoelectric Applications

“…Favier et al demonstrated that nanocompositing-associated lattice interfaces scatter thermal carriers more effectively than do grain boundaries. Therefore, adding nanoinclusions is better than producing nanograin structures to improve ZT . Thus, nanocompositing is one of the best strategies for modifying the interconnected σ, α, and κ .…”

Enhanced Thermoelectric ZT in the Tails of the Fermi Distribution via Electron Filtering by Nanoinclusions -- Model Electron Transport in Nanocomposites

“…Bulk silicon is not an efficient thermoelectric material due to its high thermal conductivity [10,11]; however, it provides an excellent platform for studying the role of design parameters on transport properties, since its bulk properties are extremely well characterized. This study is partially motivated by our recent findings suggesting that oxide inclusion, spontaneously nucleated during the sintering of silicon nanoparticles, can be effective at improving thermoelectric power conversion [12]. While the mechanism is attractive, this synthesis route is problematic since the thermodynamically driven nucleation of oxide inclusions is difficult to control, meaning that inclusions' size and density are not easily and independently tunable.…”