Microstructural and electrical properties of CuAlO2 ceramic prepared by a novel solvent-free ester elimination process

Abstract

A novel solvent–free ester elimination technique was designed for the preparation of CuAlO2 ceramic. It involved a direct reaction between aluminum sec-butoxide and copper (II) acetate in the absence of a solvent. Elimination of ester was confirmed from the sharp and intense peak at 1738 cm−1 on the FT-IR spectrum and the characteristic sweet smell obtained from the volatile by-product. The formation of Cu–O–Al mixed metal oxide bridge was demonstrated by a comparative XPS study of the as-prepared material and two separately prepared materials, one having pure Al–O bonds and the other having pure Cu–O bonds. The observed chemical shifts in of O 1s, Al 2p, Cu 2p3/2 and Cu 2p1/2 core levels and the disappearance of the Cu–O satellite peak support this formation. TG-DTA-EGA and XRD analysis revealed the mechanism that lead to the formation of a pure phase of CuAlO2 delafossite under ambient annealing at temperature of 900 °C. The BEI-EDXS and XRD information obtained for ceramic pellets made at different pressures (i.e. 10 MPa, 15 MPa and 20 MPa) also support this pure delafossite phase formation. The semiconductor behavior of the ceramics was confirmed from the temperature dependent resistivity curve and their p-type conductivity from Hall effect measurement.