Thermoelectric properties of sintered (Mn/sub y/Ni/sub 1-y/)/sub x/Fe/sub 3-x/O/sub 4/

Effects of Mn-Ni co-substitution were investigated on the thermoelectric properties of sintered magnetite (Fe/sub 3/O/sub 4/). Following the previous study, investigations were focused on the x dependence for 0/spl les/x/spl les/0.4 with y=2/3, and y dependence for 0/spl les/y/spl les/1 with x=0.2, in (Mn/sub y/Ni/sub 1-y/)/sub x/Fe/sub 3-x/O/sub 4/. Thermoelectric power factor manifested a maximum near x=0.2 and y=2/3, exceeding that of magnetite, due to a remarkable behavior of electrical resistivity in the x and y dependences. This behavior was shown to originate from that of the mobility in the framework of analysis by small-polaron hopping model. In this model, the hopping energy was shown to change at the Neel temperature.