| This work investigated the effect of titanium dioxide as a dopant on the development of grain boundary energy and microstructure in spinel (MgAl2O4). A novel "sandwich" doping geometry allowed for greater consistency among data sets. Determination of the grain boundary versus surface energy ratio was made by examining thermally induced grain boundary grooves with Atomic Force Microscopy (AFM). A method for correcting the error associated with the convolution of sample and tip geometry was extended to include small feature dimensions and large measured dihedral angles.;It was found that multiple measurements per grain boundary are statistically unnecessary, thereby reducing the overall labor required for analysis. The energy ratio of pure spinel etched in oxygen was determined to be more than double that of an identical sample etched in hydrogen at the same temperature. Pure spinel was shown to display the lowest energy ratio after annealing in hydrogen at 1100°C, while doped spinel showed a similar, but less straight forward dependence on temperature. Dopant concentration was shown to increase the energy ratio by more than 2.5 times when compared with pure samples. It was also observed that the low concentration region of doped samples displayed an increased energy ratio. Titania was observed to enhance grain growth, particularly at higher temperatures, where high concentrations resulted in precipitation of a second phase. |
