Synthesis of delafossite CuAlO_2 p-type semiconductor with a nanoparticle-based Cu(I) acetate-loaded boehmite precursor

Delafossite CuAlO_2 p-type nanostructured semiconductor was synthesized using boehmite (γ-AlOOH) nanorods loaded with copper(I) acetate [Cu(OAc)] as a precursor (nanoprecursor). Because Cu(OAc)-loaded γ-AlOOH nanorods are highly anisotropic, they tend to form inherent bunches consisting of several nanorods during the course of drying the nanoprecursor dispersion droplet on a solid substrate. By annealing the nanoprecursor at 1150 °C in air, a delafossite CuAlO_2 polycrystal was successfully obtained as the dominant phase. The CuAlO_2 polycrystal is found to exhibit the (110) crystal orientation. The crystalline anisotropy of CuAlO_2, which is not usually attainable using conventional molecular precursors, is presumably originated in the anisotropic morphology of the nanoprecursor. The Seebeck coefficient, resistivity and thermal conductivity of the CuAlO_2 polycrystal at 300 K were found to be +560 μV K^, 1.3 Ω m and 19.4 W K^ m^, respectively, confirming the p-type nature of the CuAlO_2 polycrystal