Interconnection of iron disilicide crystal structure parameters with its thermoelectric properties

The paper is devoted to the study of transport properties of the semiconductor phase of iron disilicide (/spl beta/-FeSi/sub 2/) at low temperature. A previous study of kinetic properties of /spl beta/-FeSi/sub 2/ showed that there is a very large difference in the thermoelectric properties of a number of samples of the same composition prepared by the same method. No essential difference was found between electrical conductivity at low temperature of single crystals and that of polycrystalline samples of iron disilicide. This paper shows that the smaller the lattice parameters of the sample, the smaller is its electrical conductivity at /spl sim/10 K. It is shown that the smallest electrical conductivity at this temperature corresponds to the unit cell of stoichiometric /spl beta/-FeSi/sub 2/, or a slightly smaller unit cell than the stoichiometric one. The study of specific heat and magnetic susceptibility of /spl beta/-FeSi/sub 2/ at low temperature indicates no phase transition or magnetic ordering at T = 20-25 K corresponding to the break in temperature dependence of electrical conductivity.