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Improving Thermal Stability of High TC YBCO Superconductor Using Iso Thermal Annealing in Purified Helium

IP.com Disclosure Number: IPCOM000109371D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 59K

Publishing Venue

IBM

Related People

Shi, LT: AUTHOR [+2]

Abstract

Disclosed is a process to improve the thermal stability of YBa2Cu3O7-w (123 YBCO) high Tc superconductor in order to withstand elevated temperature processing treatments without losing superconducting properties. It has been verified that the superconducting properties of 123 YBCO mainly depend on the oxygen concentration in the oxide. The closer to 7 the oxygen stoichiometry, the better the superconducting and the normal conducting properties of 123 YBCO. However, it has been observed that 123 YBCO can lose a significant amount of oxygen when heated to elevated temperatures. This causes a major concern of 123 YBCO whether its superconductivity can be retained during the processes at elevated temperatures.

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Improving Thermal Stability of High TC YBCO Superconductor Using Iso Thermal Annealing in Purified Helium

       Disclosed is a process to improve the thermal stability
of YBa2Cu3O7-w (123 YBCO) high Tc superconductor in order to
withstand elevated temperature processing treatments without losing
superconducting properties. It has been verified that the
superconducting properties of 123 YBCO mainly depend on the oxygen
concentration in the oxide.  The closer to  7 the oxygen
stoichiometry, the better the superconducting and the normal
conducting properties of 123 YBCO.  However, it has been observed
that 123 YBCO can lose a significant amount of oxygen when heated to
elevated temperatures.  This causes a major concern of 123 YBCO
whether its superconductivity can be retained during the processes at
elevated temperatures.

      It has been found (1) that a stable phase including YBa2Cu4O8
(124) and Y2Ba4Cu7O15-w (247) is formed around grain boundaries as
well as surface of 123 YBCO during isothermal annealing at elevated
temperatures in purified helium.  Since both 124 and 247 are
thermally much more stable than the 123 phase (2), this phase can be
used to improve the thermal stability of both powder and bulk 123
samples.  To do so, the  as-received 123 YBCO samples were first
annealed in ambient oxygen at 300~C to replenish any lost oxygen and
to drive out any moisture remained in the samples.  Then the samples
were annealed in purified helium (through a s...