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, 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 ( Al 0.005 Zn 0.995 O , 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.