A Multi-Step Transmission Electron Microscopy Sample Preparation Technique for Indented Ceramics having Extensive Sub-Surface Cracking

Understanding the deformation mechanisms in ceramic materials is crucial for optimizing and implementing next-generation ceramic materials in body and vehicle armor systems. One particularly powerful tool for studying deformation mechanisms is transmission electron microscopy (TEM) of impacted materials. Indentation is useful for studying deformation mechanisms, since this method offers the ability to track microstructural features as a function of depth from the indent. Preparing an indented sample for examination in TEM is extremely challenging since the sample preparation process may introduce additional cracks and artifacts. Ion beam milling processes can also induce surface damage and artifacts, such as amorphization and re-deposition of amorphous material in and on indented ceramics [1]. Amorphization should particularly be minimized, since amorphization is an inelastic deformation mechanism that has been observed in some ceramics [2]. All of these effects will change the appearance of the indentation-induced cracking and other microstructural features, therefore obscuring microstructure of the mechanically damaged area. The goal of this work was to develop a sample preparation technique for heavily cracked ceramics that preserves the true microstructure for TEM imaging and analysis.