Thermoelectric Properties and Electronic Density of States of Transition Metal Monoborides, FeB, CoB, NiB and their Solid Solutions

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Monoborides of iron, cobalt and nickel, and their solid solutions having FeB crystal structures, were prepared by solid state reaction at 950°C in a vacuum and were then HIPed using hydrothermal water as a fluid at 900°C for 2 h at 100 MPa. Electrical conductivity and Seebeck coefficients of the specimens were measured in order to evaluate thermoelectric properties. Electrical conductivities were greater than 10⁵ Sm^-1 and Seebeck coefficients range from +20 to -30 μVK^-1 as metal atoms changed. The electrical densities of states of these borides were calculated by a first principle method (DV-Xα). The Fermi level of these borides was near the 3d orbital of the metal atom and this seemed to be a reason for the relatively high Seebeck coefficients.