Solid state synthesis of nano-boehmite-derived CuAlO2 powder and processing of the ceramics

The delafossite CuAlO2 powder was prepared from the nano-boehmite AlOOH·xH2O and Cu2O by the solid state synthesis at 1100 °C in argon. The inherently slow solid state reaction was accelerated by introducing rod-like boehmite nano-particles which fully covered the 1 μm sized Cu2O particles in the reactant mixture, and decomposition of the nano-boehmite upon calcination. In contrast, the reaction between the Cu2O and Al2O3, introduced as a reference, resulted in mixed phases under the same experimental conditions. Sintering of the nano-boehmite derived CuAlO2 powder compact at 1100 °C for 2 h in air resulted in the delafossite ceramic with 86% of theoretical density, without any impurities detectable by X-ray diffraction analysis. The analysis of the microstructure by scanning electron microscopy confirmed that the bulk of the sintered sample was delafossite phase with uniformly distributed porosity, with only traces of Cu-rich impurities at the surface.