Effects of Mn and/or Ni substitutions for Fe on thermoelectric properties of magnetite prepared by sintering

Effects of Mn and/or Ni substitutions for Fe were investigated on thermoelectric properties in sintered magnetite (Fe/sub 3/O/sub 4/) for temperature range 200-700/spl deg/C. Substitutions were performed in 4 series; (1) Mn/sub x/Fe/sub 3-x/O/sub 4/ (0/spl les/x/spl les/ 0.8), (2) Ni/sub x/Fe/sub 3-x/O/sub 4/ (0/spl les/x/spl les/ 0.8), (3) (Mn/sub 1/2/Ni/sub 1/2/)/sub x/Fe/sub 3-x/O/sub 4/ (0/spl les/ x/spl les/1.2) and (4) (Mn/sub 2/3/Ni/sub 1/3/)/sub x/Fe/sub 3-x/O/sub 4/ (0/spl les/ x/spl les/ 1.2). The values of electrical resistivity (/spl rho/) and Seebeck coefficient (S) for series (1) and (2) were found to be similar to the previously reported results for magnetite single crystal. Common to the 4 series, /spl rho/ slightly decreased with temperature, and S and thermoelectric power factor S/sup 2///spl rho/ increased with temperature. For series (4) with x=0.4, there was a case the thermoelectric power factor exceeded that of magnetite.