Effect of varying mixture ratio of raw material powders on the thermoelectric properties of AlMgB14-based materials prepared by spark plasma sintering

Thermoelectric properties of AlMgB₁₄-based materials prepared by spark plasma sintering were investigated. Al, Mg, and B powders were used as raw material powders. The raw powders were mixed using a V-shaped mixer, and then the mixture was sintered at 1673 K or 1773 K. The mixture ratio of raw powders was varied around stoichiometric ratio of AlMgB₁₄. X-ray diffraction patterns of samples showed that all samples consist of AlMgB₁₄ and MgAl₂O₄. The Seebeck coefficient of the samples exhibited significant change depending on the varying mixture ratio and sintering temperature. One sample exhibited a large negative value for the Seebeck coefficient (approximately −500 μV/K) in the temperature range from 573 K to 1073 K, while others showed positive value (250–450 μV/K). Thus n-type AlMgB₁₄-based material has been realized by varying raw material ratio and sintering temperature.