We report the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr1-xMg xO2 (0 ≤ x ≤ 0.05) at temperatures in the range from 4 to 1100 K. The lattice parameter, c, linearly decreases with increasing Mg concentration in the range 0 ≤ x ≤ 0.03. This decrease is mainly caused by the shrinking of O-Cu-O dumbbells which connect the CdI2-type (Cr/Mg)O2 slabs. Magnetic susceptibility measurements indicate that Cr3+ is in the high spin state in the paramagnetic phase above 25 K. The electrical resistivity, ρ, of CuCr1-xMgxO 2 exhibits semiconducting behavior (dρ/dT < 0) in the range from 350 to 1100K, which decreases through the partial substitution of Mg 2+ for Cr3+ with 0 ≤ x ≤ 0.03. Positive and high Seebeck coefficients of CuCr1-xMgxO2 at high temperatures are consistant with the theoretical values predicted by Koshibae, who considered the spin entropy flux for the high-temperature Seebeck coefficent. From the linear S vs ln σ plot, considerable contribution from the band structure and carrier concentraton to the Seebeck coefficient is indicated. The power factor, S2σ, reaches its maximum value at around x = 0.03 in this system. The thermal conductivity, κ, for CuCr 1-xMgxO2 ranges from 6 to 10W·m -1·K-1 at 300K, slowly decreasing with increasing temperature up to 1000 K. In the present system, the maximum dimensionless figure of merit, ZT = S2T/ρκ = 0.04, is realized for the case of x = 0.03 at 950 K.
|Number of pages||5|
|Journal||Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers|
|Issue number||3 A|
|Publication status||Published - 2007 Mar 8|
- Koshibae's formula
ASJC Scopus subject areas
- Physics and Astronomy(all)