TEM sample preparation of superconducting oxides

Abstract

The preparation and observation of high Tc superconducting TEM samples deserves a great deal of care since, as when characterizing any new material, mistreatment can bring about extrinsic features leading to erroneous conclusions. In dealing with materials such as these, where the structural origins of the electromagnetic properties are tantamount, this is especially true. The three most common practices of sample preparation are suspending crushed powder, ultramicrotomy, and ion-beam milling. The illustrations will be made with YBa2Cu3O7-x samples.The powder suspension technique requires grinding the material with a suitable mortar and pestle (e g., agate) to a size which will allow electron transparency. Dispersing the particles in a suitable solvent such as water or acetone prevents aggregation. If the sample has large amounts of extraneous phases, the choice of medium is crucial as reactions will occur. Ni or Ti grids (50 to 75 mesh) with carbon films are used to fish out the suspended particles.