Solubility and diffusion of cobalt in alumina

Abstract

Di usion of Co in alumina was carried out between 1403 and 1873 K in air with or without the presence of a spinel phase. The penetration pro®les were obtained by the secondary-ion mass spectrometry (SIMS) technique and at the highest temperature by tracer measurement. The Arrhenius relationdescribes the temperature dependence of the di usion coe cient obtained by both methods. The formation of the spinel phase CoAl2O4 was observed when the experiments were carried out at temperatures lower than 1673 K. The formation of the spinel phase o ered a good opportunity to calibrate the SIMS signal and the solubility of Co in alumina was found to be about (2 4 † £ 10 ¡3 metal atom fraction in the temperature range 1403±1623 K.