Imaging grain microstructure in a model ceramic energy material with optically generated coherent acoustic phonons.

Characterization of microstructure, chemistry and function of energy materials remains a challenge for instrumentation science. This active area of research is making considerable strides with methodologies that employ bright X-rays, electron microscopy, and optical spectroscopy. However, further development of instruments capable of multimodal measurements, is necessary to reveal complex microstructure evolution in realistic environments. In this regard, laser-based instruments have a unique advantage as multiple methodologies are easily combined into a single instrument. A pump-probe method that uses optically generated acoustic phonons is expanding standard optical characterization by providing depth resolved information. Here we report on an extension of this method to image grain microstructure in ceria. Rich information regarding the orientation of individual crystallites is obtained by noting how the polarization of the probe beam influences the detected signal amplitude. When paired with other optical microscopies, this methodology will provide new perspectives for characterization of ceramic materials.