FORMATION OF ZNAL2O4 IN THE PRESENCE OF CL-2

The formation of ZnAl2O4 spinel in diffusion couples of Al2O3 and ZnO was investigated between 1000° and 1390°C in air and in air containing 4.8 vol% Cl2 by X-ray diffraction, electron probe microanalysis, and scanning electron microscopy. The rate of formation of a spinel layer obeyed a parabolic rate law and was accelerated remarkably by the presence of Cl2. The interdiffusion coefficient, D˜, and the activation energy, E, were calculated to be 10−8 to 10−9 cm2/s and 123 kcal/mol (514 kJ/mol) in air and 10−7 cm2/s and 31 kcal/mol (130 kJ/mol) in air containing 4.8 vol% Cl2, respectively. © 1988 Wiley. All rights reserved.