The effect of the simultaneous addition of Ag, Sn and Bi, totaing 4 wt%, on thermoelectric properties of a ZnSb alloy containing 47 to 54 at%Zn has been studied. ZnSb containing 53 to 54 at%Zn gives a good result. The highest value of the figure of merit
Z, 1.34×10
−3°K
−1, was obtained with the specimen containing 54 at%Zn in the base alloy and with additional elements, 2 wt%Ag, 1 wt%Sn and 1 wt%Bi. Also the specimen, 53 at%Zn in the base alloy and 2 wt%Ag and 2 wt%Sn added, has a
Z value of almost the same as that of the above mentioned specimen. An approximate relation, σ=4000×exp(−0.016α), is found between α and σ of the alloys, but several specimens show a more favorable combination of α and σ. From this relation, it is expected that alloys having α of about 125 μV/°C will have a higher
Z value, and in fact, this has been confirmed. However, the specimen having the α value of 174 μV/°C has also a very high
Z value, in agreement with Ioffe’s theoretical prediction. According to our experimental data, the
KL of ZnSb compound is estimated to be about 0.012 W °C
−1 cm
−1, but
KL seems to be reduced to about one half by the (Ag, Sn, Bi)-addition. Within the temperature range from room temperature up to 350°C, α increases with increasing temperature, while σ decreases. Combining these measured temperature variations of α and σ with presumed that of
K,
Z is expected to rise slowly with temperature and to exhibit the highest value between 200° and 300°C.
The process for preparing the ZnSb specimen by sintering has also been studied. Sintering is most satisfactorily carried out at the temperature of 25° to 30°C below the melting point of the alloy. The specimens thus prepared process the
Z values equal to or even higher than those of specimens of the same composition and prepared by melting, quenching and annealing.
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