Transmission Electron Microscopy (TEM) Characterization of doped α-Alumina

Qualitative EDX analysis: A map is acquired in low magnification. Results show equiaxial grains finely distributed through out the sample. In spite of the fact that simulations indicate no clear energetic gain or loss for cosegreation over single dopant segregation in this material, we observed that in all grain boundaries these two dopants (Y an La) are segregating together (figure 2). This could be explained by atomistically more favorable configuration for La-Y cosegregation. Tewari et al. showed in their simulation that oxygen ion is more often coordinated with one Y and one La atom than two Y or two La atoms. Also, as a result of continuous energy spectrum of different configuration in the case of cosegregation we have higher configurational entropy in this case. In the last few decades efforts have been made to obtain transparent polycrystalline α-Alumina in many research groups because of its excellent mechanical properties and chemical stability at high temperatures, also, the possibility to have it in the form of large sheets and curved shapes for a broad range of application such as watches, wave guides, armors and high temperature windows. In order to achieve high real inline transmittance (RIT), grain size and porosities should be controlled during the sintering process which is done mainly by doping the ceramics with rare earth elements such as La and Y. Therefore, distribution of these elements in microstructure of the ceramic should be studied to understand their influence on its properties. It has been shown that codoping of Y and La always lead to improvement in RIT by reducing the grain growth. The aim of this study is to investigate microstructure of codped α-alumina sample and its relationship with dopant distribution in the material. Objective