Thermoelectric pn Junction Prepared on the Route of Bulk Mechanical Alloying (特集 熱電変換材料) Thermoelectric pn Junction Prepared on the Route of Bulk Mechanical Alloying
p and n-type bismuth telluride based materials prealloyed by bulk mechanical alloying are directly hot pressed with one-step to yield thermoelectric pn junction. Variation of constitutional element concentrations across the pn interface is characterized by EPMA to determine the interface thickness of pn junction. Electrical resistivity of the interface layer is greater than that of both p and n semiconductor materials. Analytic expressions for Seebeck coefficient and figure of merit versus interface layer size are deduced. Seebeck coefficient of the pn junction is inversely proportional to the ratio of interface layer length to pn junction height (h<SUB>i</SUB>/h). It agrees well with experimental result. As for a pn junction with a certain thickness of interface layer, there is a maximum figure of merit at the optimal h<SUB>i</SUB>/h; and with a decrease of the thickness of the interface, the maximum increases, correspondingly the optimal h<SUB>i</SUB>/h decreases. In other words, pn composite billet with a thinner interface layer can attain larger figure of merit at the same h<SUB>i</SUB>/h than the one with a thicker interface. Adjusting process parameter, with proper cutting, thermoelectric properties can be improved greatly, this method for pn junction is feasible.
粉体および粉末冶金 47(11), 1194-1197, 2000-11-15