W0155

Electron Diffraction at NIST. Leonid Bendersky, Materials Science and Engineering Laboratory, NIST, 100 Bureau Drive, Stop 8554 Gaithersburg, MD 20899-8554.

There are three major advantages in using electron scattering via transmission electron microscope (TEM) for crystallographic study:

• an electromagnetic lens can focus electrons to a fine probe; thus single-crystal diffraction data can be obtained from a very small volume;

• the scattering cross section for electrons is 10³-10⁴ as great as for x-rays and neutrons; thus it is possible effectively to detect saddle changes in a structure (e.g., ordering, distortions, short-range ordering);

• TEM operates in a complementary image mode, which enables direct imaging of structures and defects.

In this talk contributions of NIST’s electron microscopists in solving crystallographic problems using different methods of TEM will be presented. The most significant examples in the field of complex oxides, quasicrystals and phase transformations will be discussed.