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Preparation of Electron High Temperature Superconductors

IP.com Disclosure Number: IPCOM000122178D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Grant, P: AUTHOR [+3]

Abstract

Disclosed is a process for obtaining ceramics of electron high temperature superconductors such as Nd1.85Ce0.15CuO4, with macroscopically uniform concentrations of cerium and oxygen that result in bulk superconductors suitable for application.

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Preparation of Electron High Temperature Superconductors

      Disclosed is a process for obtaining ceramics of electron
high temperature superconductors such as Nd1.85Ce0.15CuO4, with
macroscopically uniform concentrations of cerium and oxygen that
result in bulk superconductors suitable for application.

      Ceramic samples of the newly discovered electron
superconductors (1) are difficult to prepare with uniform rare earth
and oxygen concentration throughout.  The materials obtained by the
usual procedure of calcining the oxides together at high temperatures
yield inhomogeneous samples that show no bulk superconductivity (2).

      The procedure described here involves a two-step calcination
(3) according to the following reactions:
  1 Nd2O3 + CeO2 T NdCeO3.5
  2 (1 - x)Nd2O3 + xNdCeO3.5 + CuO T Nd2-xCexCuO4 + 0.25x02I

      Step (1) is carried out in a furnace heated to 1400oC for 48
hours in air.  The resulting product is ground and mixed with the
additional constituents shown in Step (2) and then fired in a furnace
at 980oC for 24 hours in flowing oxygen. The product is then
reground, pelletized and refired at 1050oC for 48 hours in flowing
oxygen.  Step (1) forms the known compound NdCeO3.5 which is then
used in Step (2) to yield the desired product Nd2-xCexCuO4 containing
uniformly distributed Ce, and overcomes the problem encountered using
the normal one-step procedure.  The product is now annealed in
flowing argon in a sealed furnace hea...