n-p Type variation in thermoelectric AlMgB14–based materials by raw material mixture ratio

•We explored condition to change the p-type AlMgB14 into n-type.•A specific range of the raw material ratio realized an n-type AlMgB14.•The electrical conduction type of n-type materials was different from p-type ones.•Metal site occupation in the samples were analyzed by XRD and Rietveld refinement.•The number of valence electrons of n-type materials was larger than of p-type ones.

We controlled the sign of Seebeck coefficient of AlMgB14-based thermoelectric materials by changing the raw material ratio for spark plasma sintering. The raw material powders of Al, Mg and B were mixed by V-shape mixer then sintered at 1773 K. Some sintered samples exhibited negative Seebeck coefficients and the others did positive as established for stoichiometric AlMgB14. The temperature dependence of electrical conductivity was different from each other type. Rietveld refinement for XRD results about the samples revealed that Mg site in the AlMgB14-lattice was occupied more for negative materials than the p-type ones and the negative samples had more valence electron than the other.

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