JPH0437607A - Oxide superconducting material - Google Patents

Abstract

PURPOSE:To improve the superconductivity transition temp. of the material by forming a layer structure, in which a monoatomic layer consisting of Tl and O and a layer consisting essentially of a perovskite structure of Ba, Ca, Cu and O are alternately arranged, and specifying the structure of the latter layer. CONSTITUTION:This superconducting material contains a layer, in which two two-dimensional planes consisting of Cu and O in the layer of Ba, Ca, Cu and O are present and another layer, in which the three planes are present, and both layers are alternately arranged through a monoatomic layer consisting of Tl and O. The oxide superconducting material is expressed by Tl1Ba2Ca2.6 Cu3.5Ox and has a high superconductivity transition temp. Tc of >=120K, and the content of the Tl harmful to the human body can become least among the materials consisting of Tl-Ba-Ca-CU-O and having the superconductivity transition temp. of >=120K.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to oxide superconducting materials with higher superconducting transition temperatures.

Conventional technology superconducting materials have properties that other materials do not have, such as 1) zero electrical resistance below their superconducting transition temperature, 2) complete diamagnetic property and 3) Josephson effect. It is expected to have a wide range of applications, including power transport, wind power generation, fusion plasma confinement, magnetic levitation arrays, magnetic shielding, and high-speed computers. However, the superconducting transition temperature of conventional metallic superconducting materials is 2.
In actual use, it must be cooled using expensive liquid helium and a complicated insulation device, which is a major industrial problem. was carried out in 1986;
Bednorz and Mulle
Oxide-based superconducting materials (La+-zSrz) with a high superconducting transition temperature of about 40
) 2 cuo was found and since then YBaa Cu
sOx, B1-8r-Ca-Cu-Q.

Superconducting transitions at higher temperatures have been reported for Tl-Ba-Ca-Cu-0. Currently, much research has been conducted on the manufacturing methods, physical properties, applications, etc. of these materials, but the problem that the invention aims to solve is that the higher the superconducting transition temperature (hereinafter referred to as To), the easier cooling becomes, and the same It is expected that the critical current density and critical magnetic field will increase when used at high temperatures, and the range of applications is expected to expand. To achieve this object, the present invention solves the above-mentioned conventional problems and uses a new oxide superconducting material having a T of more than 100. a monoatomic layer consisting of 1tT1 and oxygen; B.

In a layered structure in which layers based on a perovskite structure consisting of Ca, Cu, and oxygen are arranged alternately, BL contains C in the layers of Ca, Cu, and oxygen.
There is a layer in which there are two two-dimensional planes made of u and oxygen, and another layer in which there are three, and these two layers are arranged alternately through monoatomic layers made of Tl and oxygen. have.

Effect: With this configuration, an oxide superconducting material having a high To of 120 or more can be obtained.9 Examples Hereinafter, an example of the present invention will be described.
3. Using CuO(7) powder These powder plates B
Weigh aCO3 and CuO so that the ratio of Ba: Cu = 1: 1, and use a vibration mill to make Zr with a diameter of 2 mm.
Using an O2 ball, pulverize and mix for 1 hour using ethanol as a dispersion medium. After mixing, dry the entire amount including the dispersion medium at 120°C in a dryer. 9. Heat the resulting powder at 900°C.
After calcining in the air, the powder was crushed in a vibrating mill for 30 minutes in the same manner as described above and dried at 120°C.1.
Analysis of this calcined powder by X-ray diffraction1. , BaCu
Confirm that O2 is being generated, and use the same method as the ninth
Weigh and mix aCO3 and CuO and calcinate at 950℃ to make Ca
Synthesize 2CuO3 powder.Weigh this BaCu0a powder, Ca2Cub3 powder, Tl2O3, and CuO powder so that they are in a predetermined ratio, and pulverize and mix the weighed powders for 1 hour using a sieve machine.9 After mixing, this powder 0.4g of 70g in a 15mm x 5mm mold
Uniaxial pressure molding was performed at a pressure of 0 kg/cm2.The resulting molded body was wrapped in Au foil and sealed in a quartz tube under reduced pressure.
Baked for ~128 hours. Temperature increase/decrease rate was 300℃.
/h to evaluate the superconductivity, the temperature change in electrical resistance was measured using the DC 4-terminal method (measurement current 10 mA) at 5QUI.
Compositions of the prepared samples (Tl: Ba: Ca:
The molar ratio of Cu) and firing conditions are shown below. Furthermore, Table 2 shows the superconducting phases in the samples investigated by X-ray diffraction. The four-digit numbers in Table 2 each indicate the molar ratio of Tl:Ba:Ca:Cu. In addition, they are arranged in descending order of peak intensity appearing on the low-angle side (3°≦2θ≦10°) of the diffraction pattern.The * mark is the crystal phase of the present invention showing a periodic structure of 17.6 people.

(Leaving space below) Table 1 Sample Composition number Tl: Ba: Ca: Cu Firing temperature Time 20°2, O: 2 leaves 20: 20: :4.4 -4.4 :44 :4.4 ・44 900℃ 900℃ 900℃ 900℃ 900℃ 840℃ (le j1 margin) Table 2 Sample number Superconducting phase No. 1 2223. 22122
2223, 1223 4 1223, Book 1 2 2.5 3
．． 5. 12345 books 1 2 2.5 3
．． 5. 1234. 12236 book 1
The samples No. 2, 2.5, 3.5 and No. 6 were almost single-phase crystals showing a periodic structure of 17.6 people (CuO and Cap CLIOJ were also clearly observed, although the peak intensity was small). When observed with a transmission electron microscope (TEM), the area where layers of 19.2 and 16.0 layers are arranged alternately (at least 20 pairs in one field of view are 61tK)
I can do M. ) was observed. Figure 1 shows the temperature characteristics of the electrical resistance and magnetic susceptibility of the thus obtained sample of the oxide superconducting material with q No. 6 in one embodiment of the present invention. The decrease in resistance value is 1
The magnetic susceptibility starts at 26K and becomes zero at 122K. Also, regarding the magnetic susceptibility, it is considered that the Tl-Ba-Ca-Cu-0 system exhibits a large demagnetization below 123K, and as a material that causes a superconducting transition above 120K. T12 Ba2C
a2Cu30x and TI+ Ba2CaaCuzOx are known. The material of the present invention is T1+Ba2Ca2.
5Cu3. It can be written as sOx, Tl-Ba-Ca-
As a material that causes a superconducting transition in 120 or more consisting of Cu-0 (the content of T1, which is harmful to the friend body, is the lowest (
X.

Effects of the Invention As described above, the present invention provides a layered structure in which monoatomic layers consisting of Lt, Tl or oxygen and layers based on a perovskite structure consisting of Ba, Ca, Cu and oxygen are arranged alternately. In, BL CL Cu
In the oxygen layer, there is a layer in which two two-dimensional planes made of Cu and oxygen exist, and another layer in which three two-dimensional planes exist, and these two layers are alternately interposed through a monoatomic layer made of T1 and oxygen. Is it arranged and has a high To of 120 or more? ,Z
, Tl-Ba-Ca-Cu-0, which is an excellent oxide superconducting material that has the lowest content of Tl, which is harmful to the human body, among the materials that undergo a superconducting transition at a temperature of 120 or more.

[Brief explanation of drawings]

Figure 1 is a temperature characteristic diagram of electrical resistance and magnetic susceptibility of an oxide superconducting material in one embodiment of the present invention.
Patent attorney Shigetaka Awano et al.] Figure 1 Temperature CK)

Claims (1)

[Claims] A layered structure in which monoatomic layers consisting of thallium (Tl) and oxygen and layers based on a perovskite structure consisting of barium (Ba), calcium (Ca), copper (Cu) and oxygen are arranged alternately. In, Ba, Ca,
In the Cu and oxygen layer, there is a layer in which two two-dimensional planes made of Cu and oxygen exist, and another layer in which three two-dimensional planes exist, and these two layers alternate with one atomic layer made of Tl and oxygen interposed in between. An oxide superconducting material arranged in