Thermoelectric Property of Polycrystalline Aluminum‐Doped Zinc Oxide Enhanced by Micropore Foaming

Abstract

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, κ, decreased on addition of both precursors, increasing the porosity. Electric conductivity, σ, 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 (Al0.005Zn0.995O, 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.