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Melt-produced high temperature rare earth barium copper oxide superconductor and processes for making same
| Details |
Inventors: Hermann, Allen M.; Sheng, Zhengzhi;
Assignee: University of Arkansas (Fayetteville, AR)
Primary Examiner: Albrecht; Dennis
Assistant Examiner:
Attorney, Agent or Firm: Hill, Van Santen, Steadman & Simpson
A class of melt-produced, high temperature suerpconductors and processes of making same are provided. The superconductor has a preferred composition of R-Ba-Cu-O wherein R is chosen from the group of rare earth metals excluding: Praseodyium; Cerium; and Terbium. The process is carried out at a relatively low temperature of about 950.degree. C., and the process allows fabrication of melt-produced high temperature superconductors of arbitrary shape. The process is based on the reaction between molten barium-copper oxides and solid rare earth oxides, rare earth barium oxides, rare earth copper oxides, or rare earth barium-copper oxides. In an embodiment, the method comprises the steps of: mixing and grinding BaCO.sub.3 and CuO with other nominal compositions; pressing the resultant mixture into a pellet, if necessary; placing the pellet or powder on a pellet or powder that can include rare earth copper oxides; heating the pellet and/or powders to a temperature of approximately 950.degree. C.; and removing a melt-produced superconductor from the remaining powder or pellet. |
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DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS The present invention provides a melt-produced, high temperature superconductor and process for making same.
As used herein, the term "high temperature" refers to a temperature above the boiling temperature of nitrogen.
It has been found that the melt-produced, high temperature supeconductor of the present invention upon reaction of the molten and solid constituents is superconducting with a critical temperature of at least 90.
degree.
K.
The melt-produced, high temperature superconductor composition of the present invention preferably has the formula: R-Ba--Cu-O wherein: R is chosen from the group of rare earth metals excluding: Praseodymium (Pr); Terbium (Tb); and Cerium (Ce).
Preferably, R is a rare earth metal chosen from the group consisting of: Yttrium (Y); Gadolinium (Gd); Erbirum (Er); Holmium (Ho); Neodymium (Nd); Samarium (Sm); Europium (Eu); Ytterbium (Yb); Dysoprosium (Dy); Thulium (Tm); and Lutetium (Lu).
In a preferred embodiment, R is Yttrium.
Preferably, the melt-produced, high temperature superconductor has the following nominal stoichiometry: RBa.
sub.
2 Cu.
sub.
3 O.
sub.
6.
5 wherein: R is a rare earth metal exlucing: Tb; Pr; and Ce and preferably: Y; Gd; Er; Ho; Nd; Sm; Eu; Yb; Dy; Tm; and Lu.
In a preferred embodiment, the melt produced, high temperature supeconductor has the following nominal stoichiometry: YBa.
sub.
2 Cu.
sub.
3 O.
sub.
6.
5.
The present invention provides methods for making meltproduced high temperature superconductors at temperatures as low as 950.
degree.
C.
By way of example, and not limitation, examples of the methods of making the melt-produced, high temperature superconductors will now be given.
EXAMPLE 1 A.
Y.
sub.
2 O.
sub.
3, BaCO.
sub.
3, and CuO with nominal compositions of Ba.
sub.
2 Cu.
sub.
3 O.
sub.
5 and Y.
sub.
1.
2 Ba.
sub.
0.
8 CuO.
sub.
3.
6 were mixed and ground in an agate mortar.
The powders were heated to approximately 900.
degree.
C.
in air for approximately 12 to about 24 hours.
B.
The heated mixtures were then reground
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