焼結熱電素子における粉末酸化の影響

Abstract

The effects of factors relating to powder oxidation of sintered Bi2Te3 thermoelements (N type) and the mechanism of the oxidation have been studied. First, the factors which seem to affect the powder oxidation were picked up by a statistical design method and their effects on the specific resistivity ρ, thermoelectric power α and α2⁄ρ were investigated by means of variation analysis. Then, the effects of the factors great in influence were exarained in detail in connection with the effect of the interval between powder production and sintering. As a result of the experiment, it was made clear that the effects of the humidity and temperature during the powder production and of the particle size were remarkable.The higher the humidity and temperature and the smaller the particle size, the lower the specific resistivity. Besides, the thermoelectric power and specific resistivity of the sintered elements decreased with the interval between powder production and sintering, but the lower the temperature and humidity during powder production, the more remarkable the tendency of decrease. The decreases in specific resistivity and thermoelectric power of sintered elements due to the powder oxidation was thought to be the donor operation of oxygen atoms occupying Te atom sites in the Bi2Te3 crystal. From the time dependence of electron concentration in the green compacts it was clarified that the increase in the electron concentration occourred during sintering.