Characterization of Materials by Transmission Electron Microscopy

The transmission electron microscope (TEM) is a very versatile tool for probing the different aspects of microstructure of a material. Starting from the basic information like morphology of the phases and the number of phases it can provide very specific and otherwise difficult to get data about the local composition and even the chemical state of the atoms present in the specimen. Structural information can be obtained from the TEM indirectly by making use of the various diffraction techniques available in the TEM. Direct information about structure is obtainable by high-resolution electron microscopy (HREM). It can reveal the nature of crystallographic defects. TEM is capable of yielding composition analysis at nano level. It is very suitable for examining the initial stages of transformation. It is equally powerful in analyzing the structure of interfaces. A recently developed technique known as fluctuation microscopy in the TEM has been found to be very useful in ascertaining the medium range order in amorphous materials. With its multifaceted capabilities such as nano-beam diffraction and composition analysis and imaging abilities at angstrom level, it has emerged as an instrument for complete characterization of microstructure of materials. The modern TEM has been taken to new heights of performance with the aid of the aberration correction and monochromator technologies. This presentation describes the different abilities of a modern TEM. The improvements in these capabilities with aberration correction and monochromator technologies have been described. The level of advancement in the country vis-a-vis the rest of the world in this area is discussed. Examples have been cited from electron microscopy of a wide variety of materials.