US 5,308,799 A · Oxide superconductor and process for preparation thereof

Abstract

The present invention relates to an oxide superconductor comprising a composite oxide of RE , Ba and Cu, wherein the superconductor comprises a micro structure comprised of a monocrystalline REBa.sub.2 Cu.sub.3 O.sub.7-x phase (123 phase) and a RE.sub.2 BaCuO.sub.5 phase (211 phase) finely dispersed therein, the 123 phase being formed in a plurality of domains respectively for individual RE compositions and in the order of the 123 phase forming temperatures in respective layers. The present invention relates also to a process for the preparation of an oxide superconductor, characterized by forming a layer from a mixed powder of the RE, Ba and Cu compounds, forming another layer(s) of a mixed powder of RE, Ba and Cu compounds having another RE composition(s) different from the above-mentioned RE composition in the 123 phase forming temperature to form a multi layer structure, putting said plurality of layers on top of one another so that the 123 phase forming temperatures in respective layers continue towards a higher temperature side or a lower temperature side, subjecting the assembly to press molding to form a precursor, putting said precursor on a supporting material with the layer having the highest 123 phase forming temperature being located at the highest position, heating said precursor to a temperature range in a solid liquid coexisting region to bring said precursor into a semi molten state, and either gradually cooling said precursor in a 123 phase temperature range or inoculating the precursor with a seed crystal and gradually cooling the inoculated precursor in the above mentioned temperature range to grow a 123 phase crystal at a growth rate of 5 mm/hr or less.

Claims16

Dependent claims

A superconductor comprising a composite oxide of at least two RE elements selected from the group consisting of Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and also Ba and Cu, wherein said superconductor comprises a micro structure comprised of a monocrystalline 123 phase of REBa.sub.2 Cu.sub.3 O.sub.7-x and a 211 phase of RE.sub.2 BaCuO.sub.5 finely dispersed therein, said 123 phase being formed in a plurality of domains respectively for different RE compositions and wherein said domains are arranged on top of one another in a successively increasing or decreasing order of their respective 123 phase forming temperatures.

A process for the preparation of an oxide high temperature superconductor, which comprises

mixing oxides, which may include a composite oxide, of RE, Ba and Cu with each other to produce a mixed powder of a first RE composition so that the molar ratio of metal elements RE, Ba and Cu falls within a region defined by connecting points (10, 60, 30), (10, 20, 70) and (50, 20, 30) to each other on a ternary equilibrium phase diagram,
forming a first layer of said first RE composition,
forming another layer(s) containing a second RE composition within said region, having a different 123 phase forming temperature than said first RE composition contained in said first layer,
putting the resultant plurality of layers on top of one another in a successively increasing or decreasing order of their respective 123 phase forming temperatures,
subjecting the resultant assembly to press molding to form a first precursor,
putting said precursor on a supporting material with the layer having the highest 123 phase forming temperature being farthest from said supporting material,
heating said precursor to a temperature range in a solid-liquid coexisting region to bring said precursor into a semi-molten state, and
gradually cooling said precursor in a 123 phase temperature range to grow a 123 phase crystal at a growth rate of 5 mm/hr or less.

5 more elements

A process for the preparation of an oxide high temperature superconductor, which comprises

mixing oxides, which may include a composite oxide, of RE, Ba and Cu with each other to produce a mixed powder of a first RE composition so that the molar ratio of metal elements RE, Ba and Cu falls within a region defined by connecting points (10, 60, 30), (10, 20, 70) and (50, 20, 30) to each other on a ternary equilibrium phase diagram,
forming a first layer of said first RE composition,
heating said first layer to 1200.degree. C. or above to form a melt,
rapidly cooling said melt to form a first molding,
forming another molding(s) through the same procedure from a mixed powder layer containing a second RE composition within said region, having a different 123 phase forming temperature than said first RE composition contained in said first layer,
putting the resultant plurality of moldings on top of one another in a successively increasing or decreasing order of their respective 123 phase forming temperatures, to form a first precursor,
putting said precursor on a supporting material with the layer having the highest 123 phase forming temperature being farthest from said supporting material,
heating said precursor to a temperature range in a solid-liquid coexisting region to bring said precursor into a semi-molten state, and
gradually cooling said precursor in a 123 phase temperature range to grow a 123 phase crystal at a growth rate of 5 mm/hr or less.

6 more elements

Dependencies are inferred from the claim text.

Oxide superconductor and process for preparation thereof

Life of this patent

Oxide superconductor and process for preparation thereof

Life of this patent

Abstract

Claims16