Questions often come up concerning the best way to prepare powders for electron diffraction analysis in the TEM. This is actually fairly simple:

• 1) Take an oxide powder, grind it up with mortar and pestie and take a carbon coated grid and swipe it across the fnes. Two glass slides can also use to grind up the powder.

• 2) A number of materials can be evaporated onto a carbon coated grid or onto a cleaved NaCI sample and then float that off on water onto a grid.

• 3) A molybdenum wire can be smoked in air to provide crys tals. If the wire is left in the smoke long enough, there will probably be enough crystal to cover a grid. Heat the wire across the terminals of an evaporator or heat with a torch to generate the white smoke. Thus MoO3 sample will pro- vide a good rotation calibration sample. Magnesium can also be burned to produce MgO crystals.