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Procedure for Obtaining Well Oxygenated, High Density Polycrystalline YBa2Cu3O7-w

IP.com Disclosure Number: IPCOM000110228D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Goland, D: AUTHOR [+3]

Abstract

Disclosed is a procedure for obtaining high density polycrystalline YBa2Cu3O7-w . It has been extremely difficult to oxygenate polycrystalline YBa2Cu3O7-w once it has densified, because, firstly, the equilibrium oxygen content is a strong function of temperature varying from O6.5 to O7 from 650~C to 450~C, and secondly, because of the very low and anisotropic diffusivity of oxygen in YBa2Cu3O7-w at 450~C, where the oxygen content is optimum.

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Procedure for Obtaining Well Oxygenated, High Density Polycrystalline YBa2Cu3O7-w

      Disclosed is a procedure for obtaining high density
polycrystalline YBa2Cu3O7-w .  It has been extremely difficult to
oxygenate polycrystalline YBa2Cu3O7-w once it has densified, because,
firstly, the equilibrium oxygen content is a strong function of
temperature varying from O6.5 to O7 from 650~C to 450~C, and
secondly, because of the very low and anisotropic diffusivity of
oxygen in YBa2Cu3O7-w at 450~C, where the oxygen content is optimum.

      The disclosed procedure involves sintering YBa2Cu3O7-w powders
at 900~C for 4 hours to obtain a 85% dense body. Such a sample has
well connected porosity.  This structure is then oxygenated at 450~C
for about 50 hours.  The well-connected porosity assures complete
oxygenation.  The specimens are then clad in silver foil (to avoid
surface interaction) and encapsulated under vacuum in a glass ampule.
The glass chosen has a softening point at around 450~C.  The
encapsulated specimens are then Hot Isostatically Pressed (HIP'ed) at
450~-460~C at a pressure around 25 GPa.  The glass flows and
transfers the pressure to the silver clad pellet.  The resulting
specimens are fully dense and well oxygenated because the oxygen does
not escape from YAa2Cu3O7-w structure at 460~C.

      The superconducting properties of such YBa2Cu3O7-w specimen are
vastly superior to YBaCu3O7-w produced by conventional procedures,
and the hydrostatic na...