The YBCO nanopowders are prepared using the sol-gel method with vacuum or Ar annealing. The end result is powder with particle size of about 50 nm. The powders are fully superconducting with Tc = 92 K. A high resolution TEM image of a single YBCO nanoparticle shows the facets and perfect crystallization of the particle all the way to the edges.
The size distribution of the nanoparticles shows the particles to be predominately less than 5 nm thick and about 50-100 nm wide 'pancakes'.
When the particles are divided by size to different groups a clear difference can be seen in the susceptibilities. The result is fully explained by the Meissner effect, when the particle dimensions are smaller than the London penetration depths. The difference seen in the zero field cooled (ZFC) and field cooled (FC) curves in the original (O) powder is due to weak links between the particles. The weak links dissappear during the segregation process.
- E. Blinov, V. G. Fleisher, H. Huhtinen, R. Laiho, E. Lähderanta, P. Paturi, Yu. P. Stepanov and L. Vlasenko, Preparation of one to three unit cell thick YBa2Cu3O7-d powders and investigation of their magnetic and microwave properties, Supercond. Sci. Technol. 10, 818 (1997).
- Raittila, H. Huhtinen, P. Paturi and Yu. P. Stepanov, Preparation of superconducting YBa2Cu3O7-d nanopowder by deoxydation in Ar before final oxygenation, Physica C 371, 90 (2002).
- P. Paturi, J. Raittila, H. Huhtinen, V.-P. Huhtala and R. Laiho, Size dependent properties of YBCO nanopowder, Journal of Physics: Condensed Matter 15, 1 (2003).