Fast consolidation of ceramic powders

Very fast densification of ceramic powders (alpha-alumina, aluminum nitride, and YBCO superconducting oxides) using prior electric discharge before resistance sintering leads to microstructures that retain the particle size of the starting powders. The time taken to achieve near-theoretical density can be as little as 5 min and usually not more than 15 min. The short time is the principal reason for arresting possible grain growth and the electric discharge step may perhaps be responsible for sweeping off impurities from powder surfaces, thus giving clean grain boundaries in the sintered material. In the YBCO powders the surface effect appears to create a filamentary layer that gives unexpectedly high (240 to 300 K) resistivity onsets and diamagnetic behavior.