JPH03295807A - Oxide superconducting material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a Tl-contg. oxide superconducting material having specified crystal structures and >=100K critical temp. CONSTITUTION:This oxide superconducting material is a laminar compd. formed by alternately arranging Tl-O layers each based on rock-salt structure and Ba-Ca-Cu-O layers each based on perovskite structure. The Tl-O layers are alternately arranged single-atom and two-atom layers. This oxide superconducting material is obtd. by firing at <=850 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an oxide superconducting material with a high superconducting transition temperature.

(Prior Art) Superconducting materials 1) have zero electrical resistance, and 2) are completely diamagnetic. 3) There is a Josephson effect.

It has properties not found in other materials, and is expected to have a wide range of applications, including power transportation, power generators, fusion plasma confinement, magnetic levitation trains, magnetic shielding, and high-speed computers. However, in conventional metallic superconductors, even the highest superconducting transition temperature is around 23';
During actual use, expensive liquid helium and large-scale insulation equipment had to be used for cooling, which was a major industrial problem.

For this reason, research has been underway to find materials that become superconductors at higher temperatures.

In 1986, B ednorz and M.
Mueller discovered Cu0x, an oxide-based superconducting material (La, -U5rz), which has a high superconducting transition temperature of about 40', and since then YBa, C
u30. ．． B1-8r-Ca-Cu-0,Ti! -Ba
Superconducting transitions at higher temperatures have been reported in -Ca-Cu-0 and the like. Currently, much research is being conducted on the manufacturing methods, physical properties, applications, etc. of these materials.

(Problem to be solved by the invention) It is expected that the higher the superconducting transition temperature (Te), the easier the cooling, and the larger the critical current density and critical magnetic field when used at the same temperature. It is expected that this will spread.

An object of the present invention is to provide a new oxide superconducting material having a Tc of 100'' or more, which has a wider range of applications than conventional materials, and a method for manufacturing the same.

(Means for Solving the Problems) The oxide superconducting material of the present invention has alternating layers based on a rock salt structure of 'l and oxygen and layers based on a perovskite structure of Ba, Ca, Cu, and oxygen. In the arranged layered compound, there are two types of 'l and oxygen layers, 1 atomic layer and 2 atomic layer, and these are arranged alternately, and the manufacturing method is to bake at a temperature of 850 ° C or less This is obtained by

(Function) As a result of intensive exploration and research into oxide high-temperature superconductors, it was discovered that the above-mentioned material is a superconductor having a high Tc of 100' or more.

(Example) As a starting material, T'z Os m with a purity of 99% or more
BaCoat CaC0, CuO powder is used.

Among these powders, Ba COs and CuO are
:Cu=1:1 ratio, and pulverized and mixed in a vibrating mill for 1 hour using a ZrO ball with a diameter of 2 cm and using ethanol as a dispersion medium. After the mixing was completed, the entire amount including the dispersion medium was dried at 120° C. in a dryer. The obtained powder was calcined in air at 900°C for 5 hours, then ground in a vibration mill for 30 minutes in the same manner as described above, and dried at 120°C. This calcined powder was analyzed by X-ray diffraction, and B a
After confirming that CuOx was generated, powders of Ca and CuO were synthesized from CaCO and CuO by calcining at 950°C using the same method. This B a C
u O, and Ca, CuO, powder obubi'f (1, IO,
, CuO powder were each weighed in a predetermined ratio.

The weighed powders were pulverized and mixed for 1 hour using a miller. After the mixing was completed, 0.4 g of this powder was uniaxially pressed in a 15 x 5 m mold at a pressure of 700 kg/a#.

This molded body was wrapped in Au [, sealed in a quartz tube under reduced pressure, and heated to 750°C to 950°C in an electric furnace.
It was baked for 1 to 48 hours. The temperature increase/decrease rate is 300 in both cases.
It was set as °C/h.

To evaluate superconductivity, we used the DC 4-terminal method (measuring current 10 mA).
), and the magnetic susceptibility was measured using 5QUID (external magnetic field 100e).

The table shows the composition of the prepared samples (T(!: Ba: Ca:
The molar ratio of Cu) and firing conditions are shown below.

Table, sample preparation condition number Ta: Ba: Ca: Cu
Temperature Time &1 22°2.0 2 2.3'2.0 3 22°2.0 4 142.0 5 14: 2.0 6 14.2.0 7 14.2.0 8 14: 2.0 9 14.2.0 3144 905℃ 2838 900℃ 3144 910℃ 51.5.4 900℃ 51”54 850℃ 5.1.54 850℃ 51°54 850℃ 5.1.54 800℃ 5.1 54 750℃ h h h 0h h 0h 8h 8h 8h When the crystal structure was investigated by X-ray diffraction, it was found that Na 1-4
The sample is almost T a2 B a, Ca, Cu30x
It was confirmed that it was single phase. On the other hand, the Na5 sample is '
r22Ba, Ca, Cu, Ox (C axis of unit cell in 36 people.

Tll and stratification from 0 are lined up in a cycle of 18 people) and '1. Ba
.

Ca2Cu30. (The C axis of the unit cell was 16 people) and was in a mixed phase. &6~9 samples Td, Ba2Ca2Cu,
Ox.

T II I B a z C a z Cu z Ox
and 34 (=18+16) peaks showing a periodic structure were observed. Especially in &8, the 34-person periodic structure was the main phase. A sample of Na 8 was subjected to a transmission electron microscope (T
When observed with EM), there were areas where layers of 18 and 16 layers were arranged alternately (at least 15 pairs could be seen in one field of view). A 34-person periodic structure was also observed in the Na 7-9 samples.

Figure 1 shows the temperature characteristics of resistance and magnetic susceptibility for 41.4 and 5.8. The temperature at which resistance reaches zero is slightly higher for &8 than for 41 and 4.5, which seems to be an onset. The decrease in resistance value started from 130″K. Also, regarding the magnetic susceptibility, Nci8 maintained larger demagnetization up to the vicinity of Tc.

(Effect of the invention) The present invention has a layer based on a rock salt structure of Ta and oxygen, Ba,
In a layered compound in which layers based on a perovskite structure of Ca, Cu, and oxygen are arranged alternately, there are two types of layers of Ta and oxygen, 1 atomic layer and 2M layer, and oxide superlayers in which these layers are arranged alternately. It is a conductive material. As a manufacturing method, it is obtained by firing at a temperature of 850° C. or lower.

This material exhibits good superconductivity with a higher Tc and less deterioration of superconductivity in the vicinity of Tc than conventionally known materials, and its effects are significant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the temperature characteristics of electrical resistance and magnetic susceptibility.

Claims (2)

[Claims] (1) Layer based on rock salt structure of Tl and oxygen and Ba, C
In a layered compound in which layers based on a perovskite structure of a, Cu, and oxygen are arranged alternately, there are two types of Tl and oxygen layers, 1-atomic layer and 2-atomic layer, and these are arranged alternately. Features of oxide superconducting materials. (2) The method for producing an oxide superconducting material according to claim (1), characterized in that the firing is performed at a temperature of 850° C. or lower.