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The effect of interstitial and vacancies on the electronic structure and electronic transport properties of Zn(4)Sb(3)

By using first-principles DFT computations, we deconvoluted structural information on Zn(4)Sb(3) from the space-time data averaging inherent to X-ray structural determination. We found that the material is a 0.184:0.420:0.396 mixture of 12-Zn atom cells and two kinds of 13-atoms cells, one with one vacancy and two interstitial Zn atoms, the other with two vacancies and three interstitial Zn atoms, respect to highly symmetric Zn12Sb10.

We demonstrate that interstitial Zn atoms do the trick in Zn(4)Sb(3). They supply electrons and enhance the thermopower, besides lowering thermal conductivity. Adding interstitials to the 12-Zn structure yields a change from p- to n-doping. Zn12.82Sb10, with interstitials in 82% of the cells, is a p-doped semiconductor whose thermopower is very sensitive to composition and/or doping.

We demonstrate the extreme sensitivity of electronic transport properties to subtle changes in the material composition. We find a maximum Z(e)T value of 4.68 at T=670K, for a p-doping level of 0.01h/cell with respect to Zn(13)Sb(10). This corresponds to Zn(12.995)Sb(10) stoichiometry, if the doping level is modified by adding interstitial Zn atoms only. A maximum ZT value of 2.11,at T=670K, is estimated from Z(e)T, assuming the lattice contribution to the total thermal conductivity independent of doping level.

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Reported by

Italian National Research Council
Via Golgi 19
20133 Milano
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