Thermoelectric properties of phase pure boron carbide prepared by a solution-based method

Abstract

In this work, we report the thermoelectric properties of phase-pure carbon-rich boron carbide B_4.05C synthesised from a sucrose precursor (here noted as ‘High Purity’ boron carbide) by a solution-based method. Three different kinds of commercially available boron carbide powders were also investigated as references. All samples were densified by spark plasma sintering at 50 MPa and at temperatures ranging from 1800°C to 2000°C. The newly synthesised boron carbide showed good sintering behaviour thanks to its small spherical grains, resulting in excellent relative densities >99%. Measurement of thermoelectric performance gave results comparable to previous reports of carbon-rich boron carbides. The High Purity boron carbide sample as well as investigated commercial reference materials showed high positive Seebeck coefficients close to 250 μVK⁻¹ over the whole temperature range. Electrical conduction mechanisms of boron carbide is also discussed. The nearest-neighbour hopping conduction model may be a better description compared to the often-used bipolaron model.