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

Abstract

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.