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Preparation and study of the thermoelectric properties of nanocrystalline Sn1−xTaxO2 (0 ≤ x ≤ 0.04)

Sn1–xTaxO2 (0 ≤ xnominal ≤ 0.04) nanoparticles, smaller than 10 nm, were synthesized by co‐precipitation method. The solubility limit of Ta (about 0.8% mol) was carefully studied by combination of XRD, SEM, and ICP analysis. The obtained powders were sintered by using the spark plasma sintering (SPS) technique, leading to dense pellets (∼95–97% density), composed of 50–70 nm grains. XPS results suggest that no Sn2+ is present in our samples and that the carbon contamination as well as oxygen vacancies, issues from SPS, are not completely removed with a post‐SPS heat treatment at 873 K. However, this small carbon contamination does not significantly influence the electrical properties. Thermoelectric properties were investigated and the best composition was found to be Sn0.99Ta0.01O2 (x = 0.01), with ρ = 4 × 10−3 Ωcm, S = −46 μVK−1, and κ ∼ 7 WK−1 m−1, at room temperature. This low thermal conductivity, as compared to those of micro‐sized SnO2‐based materials in the literature, is explained by the nanocrystalline character of the samples.