The thermoelectric properties of double perovskite-type oxides Ca 2FeMoO 6 are investigated in terms of Sr substitution at the A site of the oxides. The electrical conductivity, σ, of Ca 2-xSr xFeMoO 6 (0 ≤ x ≤ 0.3) showed a metallic behavior, decreasing monotonically from ca. 10 3 S cm -1 at room temperature to ca. 10 2 S cm -1 at 1250 K. At room temperature, although the σ values of the oxides increased with increasing substitution level, x, the σ values maintained almost the same values at high temperature range of 1000-1250 K. The absolute values of the Seebeck coefficient, S, for the samples at x < 0.3 abruptly increase at around 1000 K. The Rietveld refinement of the XRD patterns of the oxides indicated that the anti-site defects in the oxides decreased with increasing Sr concentration. The power factor, S 2σ, of the oxides largely increased with increasing temperature; the S 2σ value of Ca 2FeMoO 6 was ca. 0.35 mW mK -2 at 1200 K, the largest value of all the samples in this study. Although the thermal conductivity, κ, of the oxides generally decreased from ca. 3.5 to 4.5 W mK -1 at room temperature to ca. 2-3 W mK -1 at 1050 K, the sample at x = 0.3 showed the lowest and most T-independent κ values, implying that the relative increase in the temperature is independent from the phonon-impurity scattering caused by the A-site substitution. The power factor of the oxides increased above 900 K; thereby, the dimensionless figure of merit, ZT = (S 2σ/κ)T, significantly increased at the same temperature range. The largest ZT value of 0.15 was observed for Ca 2FeMoO 6, Ca 1.9Sr 0.1FeMoO 6, and Ca 1.8Sr 0.2FeMoO 6 at 1250 K.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics