# US 5,705,457 A · Oxide superconductor and method for manufacturing the same

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- Number: US 5,705,457 A
- Document ID: US5705457A
- Status: Granted
- Kind: A
- Application number: 08/525,912
- Filed: 1995-09-08
- Granted: 1998-01-06
- Earliest claimed: 1994-09-13
- Assignees: Furukawa Electric Co., Ltd.; Matsushita Electric Industrial Co., Ltd.; International Superconductivity Technology Center
- Inventors: Toshiyuki Tamura; Seiji Adachi; Xiao-Jing Wu; Hisao Yamauchi
- Web page: https://patentgrep.com/patent/US5705457A

## CPC

- C04B 35/45: based on copper oxide or solid solutions thereof with other oxides
- C04B 35/645: Pressure sintering
- Y10S 505/742: Annealing
- Y10S 505/776: Containing transition metal oxide with rare earth or alkaline earth
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention provides an oxide superconductor which is expressed in the composition formula (Pb.sub.1-x-y M.sub.x (A1).sub.y)(A2).sub.2 (A3).sub.n-1 (Cu).sub.n (O).sub.2n+3+z (wherein 0.ltoreq.0.6, 0.ltoreq.y.ltoreq.0.6, x+y.ltoreq.0.6, n denotes integers of 1 or more, -0.6.ltoreq.z.ltoreq.0.5, M denotes Cu or Cd, and A1, A2 and A3 denote at least one element of Ba, Sr, and Ca, respectively) and which has a crystal structure stacking rock salt structure based portions and infinite layer structure portions, wherein the rock salt structure based portion has a structure that an atoms layer having 0.5-1.5 oxygen atoms, in case the total atoms number of Pb, M and A1 is one, and an atoms layer having one or less oxygen atoms per one A2 atom, are stacked and the infinite layer structure portion has a structure that an atoms layer having 2 oxygen atoms per one Cu atom and an atoms layer of A3 atoms only, are stacked. Further, the present invention provides a method for manufacturing the above oxide superconductor by heat-treating a raw material of oxide superconductor at a temperature of 800.degree.-1200.degree. C. under superhigh pressure of 2-8 GPa.

## Claims

### Claim 1

An oxide superconductor comprising a composition of the formula:
(Pb.sub.1-x-y M.sub.x (A1).sub.y)(A2).sub.2 (A3).sub.n-1 (Cu).sub.n (O).sub.2n+3+z
wherein
0.ltoreq.x.ltoreq.0.6,
0.ltoreq.y.ltoreq.0.6,
x+y.ltoreq.0.6,
n is an integer of 3 or 4,
-0.6.ltoreq.z.ltoreq.0.5,
M is Cu or Cd and
A1, A2 and A3 are each independently one element selected from the group consisting of Ba, Sr and Ca,
the oxide superconductor having a crystal structure comprising stacked layers in the following order: a first rock salt structure portion, an infinite layer structure stacked on the first rock salt structure portion and a second rock salt structure portion stacked on the infinite layer structure, the first rock salt structure portion and the second rock salt structure portion each comprising a (Pb, M, A1)-oxygen layer stacked on an A2-oxygen layer, said (Pb, M, A1)-oxygen layer having a ratio of the total number of atoms of Pb, M and A1 to the number of oxygen atoms of 1:0.5 to 1.5, said A2-oxygen layer having a ratio of the number of A2 atoms to the number of oxygen atoms of 1:1 or less, the infinite layer structure comprising a Cu-oxygen layer stacked on a layer of A3, the Cu-oxygen layer having a ratio of the number of copper atoms to the number of oxygen atoms of 1:2, wherein said composition is made by a process comprising the step of heat treating at 800.degree. C. to 1200.degree. C. under a superhigh pressure of 2 to 8 GPa.

### Claim 2 (depends on 1)

The oxide superconductor according to claim 1, wherein said M is Cu, said A2 is Sr or Ba, said A3 is Ca, and n is 3 or 4.

### Claim 3 (depends on 1)

The oxide superconductor according to claim 1, wherein said M is Cd, said A2 is Sr or Ba, said A3 is Ca, and n is 3 or 4.

### Claim 4 (depends on 1)

The oxide superconductor according to claim 1, wherein an average valence of Cu ion is +2.05-+2.25.

### Claim 5

A method for manufacturing an oxide superconductor comprising:
heating raw materials of an oxide superconductor at a temperature of 800.degree. to 1200.degree. C. under a superhigh pressure of 2 to 8 GPa;
to prepare an oxide superconductor comprising a composition of the formula: (Pb.sub.1-x-y M.sub.x (A1).sub.y)(A2).sub.2 (A3).sub.n-1 (Cu).sub.n (O).sub.2n+3+z
wherein
0.ltoreq.x.ltoreq.0.6,
0.ltoreq.y.ltoreq.0.6,
x+y.ltoreq.0.6,
n is an integer of 3 or 4,
-0.6.ltoreq.z.ltoreq.0.5
M is Cu or Cd and
A1, A2 and A3 are each independently one element selected from the group consisting of Ba, Sr and Ca,
the oxide superconductor having a crystal structure comprising stacked layers in the following order: a first rock salt structure portion, an infinite layer structure stacked on the first rock salt structure portion and a second rock salt structure portion stacked on the infinite layer structure, the first rock salt structure portion and the second rock salt structure portion each comprising a (Pb, M, A1)-oxygen layer stacked on an A2-oxygen layer, said (Pb, M, A1)-oxygen layer having a ratio of the total number of atoms of Pb, M and A1 to the number of oxygen atoms of 1:0.5 to 1.5, said A2-oxygen layer having a ratio of the number of A2 atoms to the number of oxygen atoms of 1:1 or less, the infinite layer structure comprising a Cu-oxygen layer stacked on a layer of A3, the Cu-oxygen layer having a ratio of the number of copper atoms to the number of oxygen atoms of 1:2.

### Claim 6 (depends on 5)

The method according to claim 5, wherein said M is Cu, said A2 is Sr or Ba, said A3 is Ca, and n is 3 or 4.

### Claim 7 (depends on 5)

The method according to claim 5, wherein said M is Cd, said A2 is Sr or Ba, said A3 is Ca, and n is 3 or 4.

### Claim 8 (depends on 5)

The method according to claim 5, wherein an average valence of Cu ion is +2.05-+2.25.

### Claim 9

An oxide superconductor comprising a composition of the formula:
(Pb.sub.1-x-y M.sub.x (A1).sub.y)(A2).sub.2 (A3).sub.n-1 (Cu).sub.n (O).sub.2n+3+z
wherein
0.ltoreq.x.ltoreq.0.6,
0.ltoreq.y.ltoreq.0.6,
x+y.ltoreq.0.6,
n is an integer of 3 or 4,
-0.6.ltoreq.z.ltoreq.0.5,
M is Cd and x is defined as follows: 0.1.ltoreq.x.ltoreq.0.6,
A1, A2 and A3 are each independently one element selected from the group consisting of Ba, Sr and Ca,
the oxide superconductor having a crystal structure comprising stacked layers in the following order: a first rock salt structure portion, an infinite layer structure stacked on the first rock salt structure portion and a second rock salt structure portion stacked on the infinite layer structure, the first rock salt structure portion and the second rock salt structure portion each comprising a (Pb, M, A1)-oxygen layer stacked on an A2-oxygen layer, said (Pb, M, A1)-oxygen layer having a ratio of the total number of atoms of Pb, M and A1 to the number of oxygen atoms of 1:0.5 to 1.5, said A2-oxygen layer having a ratio of the number of A2 atoms to the number of oxygen atoms of 1:1 or less, the infinite layer structure comprising a Cu-oxygen layer stacked on a layer of A3, the Cu-oxygen layer having a ratio of the number of copper atoms to the number of oxygen atoms of 1:2.

### Claim 10 (depends on 1)

The oxide superconductor according to claim 1, wherein the oxide superconductor has a formula selected from the group consisting of
(Pb.sub.0.5 Cu.sub.0.5)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.8 Cu.sub.0.2)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.4 Sr.sub.0.1)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Sr.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.1 Sr.sub.0.4)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Ca.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Ba.sub.0.5)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Ba.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.5)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.8 Cu.sub.0.2)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Sr.sub.0.5)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Sr.sub.0.25)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.5)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Ca.sub.0.25)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Ba.sub.0.5)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.25 Ba.sub.0.25)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.5)(SrBa).sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.5)(SrBa).sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cu.sub.0.5)(SrBa).sub.2 Ca.sub.2 Cu.sub.3 O.sub.3.degree.z,
(Pb.sub.0.5 Cu.sub.0.5)Sr.sub.2 Ca.sub.3 Cu.sub.4 O.sub.11+z,
(Pb.sub.0.5 Cu.sub.0.5)Ba.sub.2 Ca.sub.3 Cu.sub.4 O.sub.11+z,
(Pb.sub.0.5 Cd.sub.0.5)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.4 Sr.sub.0.1)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.25 Sr.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.1 Sr.sub.0.4)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.25 Ca.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.25 Ba.sub.0.25)Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.5)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.2)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.25 Sr.sub.0.25)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.25 Ba.sub.0.25)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.5)(SrBa).sub.2 Ca.sub.2 Cu.sub.3 O.sub.9+z,
(Pb.sub.0.5 Cd.sub.0.5)Sr.sub.2 Ca.sub.3 Cu.sub.4 O.sub.11+z and
(Pb.sub.0.5 Cd.sub.0.5)Ba.sub.2 Ca.sub.3 Cu.sub.4 O.sub.11+z.

### Claim 11 (depends on 1)

The oxide superconductor according to claim 1, wherein the oxide superconductor does not contain a rare earth element.

### Claim 12 (depends on 11)

The oxide superconductor according to claim 11, wherein the oxide superconductor does not contain Tl or Hg.

### Claim 13 (depends on 1)

The oxide superconductor according to claim 1, wherein the oxide superconductor has a critical temperature of 100K or more.

### Claim 14 (depends on 5)

The method according to claim 5, wherein M is Cd and x is defined as follows: 0.1.ltoreq.x.ltoreq.0.6.

### Claim 15 (depends on 5)

The method according to claim 5, wherein the pressure is 5 GPa.

### Claim 16 (depends on 5)

The method according to claim 5, wherein the temperature is 900.degree. C.