Thermoelectric property of polycrystalline aluminum-doped zinc oxide enhanced by micropore foaming

A unique micropore foaming technique was used to enhance the thermoelectric properties of polycrystalline aluminum-doped zinc oxide (AZO). Silicon carbide (α-SiC) and aluminum nitride (AlN) were used as foaming precursors. Thermoelectric conductivity, I, decreased on addition of both precursors, increasing the porosity. Electric conductivity, Ï, decreased upon addition of α-SiC, and subsequent addition of AlN reversed the effect. This phenomenon is due to the chemical reactions that occur upon addition of each precursor: the active oxidation of α-SiC and the decomposition reaction of AlN. The Seebeck coefficient, S, for 0.5 mol% AlN-doped AZO (Al _0.005Zn _0.995O, AZO-0.005) was more than twice that of conventional non-doped AZO. Accordingly, the power factor and the figure of merit, ZT, for the porous AlN-doped AZO-0.005 were 4.9 and 5.8 times those of the conventional polycrystalline AZO, respectively, demonstrating that the compositionally optimized porous AZO exhibited excellent thermoelectric properties at high temperatures.