On Improving Thermoelectric Properties of ZnSb Intermetallic Compound

Abstract

Homogeneous ZnSb ingot can be prepared, as earlier workers pointed out, by melting the composing elements together in an evacuated silica capsule, cooling the melt in water and subsequently annealing the frozen material at a suitable temperature. According to our observation, a relatively low temperature, 450°C for instance, is preferable as the annealing temperature. A higher temperature, 500°C for example, very frequently causes fine cracks and the thermoelectric properties of ingots are reduced.
In our experiment, ZnSb containing 51 at%Zn exhibits higher thermoelectric power and Hall mobility as well as lower electrical conductivity than those of 50 at%Zn.
Influences of Ag, Cu, In, Sn, Bi, AgI and CuBr additions on thermoelectric properties ZnSb were studied. All these additions give p-type material, and their influences are qualitatively the same, that is to say, decrease thermoelectric power α, and increase electrical conductivity σ. Ag and Cu additions have particularly analogous influences. In both cases, σ increases remarkably, but α decreases comparatively less. These two elements may be added up to 8 wt% in quantity. Being added in such a large amount, Ag gives somewhat larger α²σ than the case of Cu. Sn addition also has an effect similar to that of Ag or Cu addition, but it does not increase α²σ so remarkably as in the case of Ag or Cu. In or Bi addition exhibits rather small effect on properties of ZnSb, i.e. a very small increase of σ. AgI or CuBr addition shows an effect analogous to, but smaller than, that of Ag or Cu. Effect of halogens can hardly be recognized.
The effect of the additions described above may be interpreted to a certain extent as a result of creation of donor or acceptor and vacancies as the result of selective substitution of either Zn or Sb atoms of the added elements.