The Effects of the Growth Conditions on the Thermoelectric Properties of n-Type 90percent Bi_2Te_3-10percent Bi_2Se_3 Single Crystals Grown by the Zone Melting Method

摘要

The effects of the zone melting temperature and growth rate onthe thermoelectric properties for 0.15wt percent CdCl_2 and 0.05 wt percentCdCl_2 doped 90 percent Bi_2Te_3-10 percent Bi_2Se_3 single crystals wereinvestigated. The Seebeck coefficient and electrical resistivity of the 0.15wtpercent CdI_2 doped single crystals were initially decreased along theingots due to the condensation of iodine in the melts. The sharp increase of theSeebeck coefficient and electrical resistivity at the last-to-freeze region wereconsidered as results of the evaporation of iodine from the molten zone andthe compensation of electrons due to the formation of the antistructure defects.The figure-of-merit was enhanced with increasing the zone meltingtemperature and lowering the growth rate. The single crystels grown at thezone melting temperature of 800deg C and the growth rate of 0.1 mm/mmexhibited the maximum figure-of-merit of 2.8 X 10~(-3)/K.