## Abstract

We report the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr_{1-x}Mg _{x}O_{2} (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 CdI_{2}-type (Cr/Mg)O_{2} slabs. Magnetic susceptibility measurements indicate that Cr^{3+} is in the high spin state in the paramagnetic phase above 25 K. The electrical resistivity, ρ, of CuCr_{1-x}Mg_{x}O _{2} exhibits semiconducting behavior (dρ/dT < 0) in the range from 350 to 1100K, which decreases through the partial substitution of Mg ^{2+} for Cr^{3+} with 0 ≤ x ≤ 0.03. Positive and high Seebeck coefficients of CuCr_{1-x}Mg_{x}O_{2} 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, S^{2}σ, reaches its maximum value at around x = 0.03 in this system. The thermal conductivity, κ, for CuCr _{1-x}Mg_{x}O_{2} 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 = S^{2}T/ρκ = 0.04, is realized for the case of x = 0.03 at 950 K.

Original language | English |
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Pages (from-to) | 1071-1075 |

Number of pages | 5 |

Journal | Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers |

Volume | 46 |

Issue number | 3 A |

DOIs | |

Publication status | Published - 2007 Mar 8 |

## Keywords

- CuCrMgO
- Delafossite
- Koshibae's formula
- Thermoelectricity

## ASJC Scopus subject areas

- Engineering(all)
- Physics and Astronomy(all)