Ta-doped Sr3Ti2O7 oxide ceramics with Ruddlesden-Popper phase were fabricated by a method of solid-state-reaction in a controlled atmosphere plus spark plasma sintering (SPS), and their thermoelectric properties were investigated in the temperature range from 300 K to 1000 K. The results indicate that both the electrical resistivity ρ and absolute thermopower |S| of Sr3(Ti1-xTax)2O7 (x = 0.05, 0.1, 0.15) decrease with increasing Ta content x, which can be ascribed to the increase of the carrier concentration due to the increased doping content. Moreover, experiments show that the total thermal conductivity of the Ta-doped Sr3Ti2O7 decreases with increasing Ta content below 600 K and reaches ∼2.5 Wm−1K−1 at 1000 K, ∼17% lower than that of Nb-doped SrTiO3. The dimensionless figure of merit, ZT, increases with temperature for all samples with different Ta contents, and the largest ZT = 0.066 is achieved at1000 K for the lightly doped compound Sr3(Ti0.95Ta0.05)2O7.

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