This effect of PbO vapor on the strength of alumina was studied to determine the corrosion mechanism. Characterization of the corroded samples was carried out using X‐ray diffraction (XRD), scanning electron microscopy, strength and sound velocity measurements, weight and dimensional
changes. The strength and sound velocity of alumina decreased when exposed to PbO but weight and volume increased. Thermodynamic modeling of the PbO–Al2O3 system was carried out using the CALculation of PHAse Diagram method, which showed that three pseudo‐binary
compounds, PbAl2O4, Pb2Al2O5, and PbAl12O19 can be formed, in agreement with prior work. It was postulated that PbAl12O19 is most likely to form when alumina is exposed to PbO at sintering temperatures
and this was confirmed by XRD and energy‐dispersive analysis. The PbAl12O19 phase does not form a surface layer but rather nucleates and grows as individual crystals embedded in the alumina surface, forming a more porous structure. This surface porosity then acts
to concentrate applied stress, resulting in a lower strength. This strength degradation mechanism makes alumina kiln furniture more sensitive to thermal stresses with repeated use, explaining the observed cracking behavior.
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 2:
Piezo Kinetics Inc., 660 East Rolling Ridge Drive, Bellefonte, Pennsylvania 16823