JPH0323219A - Oxide superconducting material - Google Patents

Abstract

PURPOSE:To obtain a superconducting material having >=120K superconductivity transition temp. only by sintering in an oxygen atmosphere with high reproducibility by adding Ag to a Tl-Ba-Ca-Cu-O compd. represented by a specified chemical formula. CONSTITUTION:Ag is added to a compd. represented by chemical formula I (where x>=0.8, n>=2 and m>=3) by 0.1-30wt.% to obtain an oxide superconducting material or Ag is added to a compd. represented by chemical formula II (where 0.3<=X<=0.7, Z>=1, n>=2 and m>=3) by 0.1-30wt.% to obtain an oxide superconducting material. The resulting material consists essentially of two phases of a superconductor and metallic Ag and is a very favorable material from the viewpoint of stabilization required to put a superconducting material to practical use.

Description

[Detailed description of the invention] Industrial application field of the present invention 2) It is completely diamagnetic. 3) The Josephson effect has properties that other materials do not have, such as A, and it has already been used in superconducting magnets.
1. Even though it is used in SQUIDs, etc., and is expected to have a wide range of applications in the future, such as magnetic shielding, high-speed computers, etc., the conventional material is NbsGe.
Metal-based superconductors such as GLT. is the highest one
The temperature is about 3K, and in actual use, it must be cooled using expensive liquid helium and a complicated insulation device, which is a major industrial problem. 1 9 8 6
Bednorz (Hednorz 7) and Muller
(Mueller) has a high T. of about 40K. Oxide-based superconducting material (L a + -zS r 2) 2
C u OX is found, then YB a2c u
0-, Bi-Sr-Ca-Cu-0, TI-Ba-C
Even though superconducting transitions at higher temperatures have been reported in materials such as a-Cu-0, the higher T is, the easier cooling becomes, and the critical current density and critical magnetic field become larger when used at the same temperature. Although it is expected that the range of application will expand, the present invention is applicable to oxide superconductors with a T of 120K or more.
Regarding TI-based materials that have Covering the periphery of the superconductor with a material with low electrical resistance (a) Introducing a pinning center to prevent the movement of magnetic flux in the superconductor, etc. Problems to be Solved by the Invention Materials with To of 120 K or more are TI. However, such high T. J, this data can only be obtained from samples manufactured by complicated methods such as sealing them in sealed containers such as quartz tubes and burning them.In addition, the data is very sensitive to manufacturing conditions and has poor reproducibility. Means for solving the problem Chemical formula TI-Ba*CaIICu. 0- (but 0.
8≦x, 2≦n, 3≦m), Ag is 0.1
~30% by weight added oxide superconducting material and Susumata 4 friends Chemical formula T 1 (1-Xl・IP b++S rsC
aIIcusov(0.3≦x≦0.7,
l≦Z. 2≦n, 3≦m), Ag is 0.
According to the present invention, the oxide superconducting material added in an amount of 1 to 30% by weight can produce 1
An oxide superconducting material having To of 20K or higher can be produced with good reproducibility.Example 1 Using bX. Weigh and mix Ba:Cu so that the molar ratio is 1=1, and burn it in air at 900°C for 10 hours LBaCu
Combine O2 and CaCOs with a purity of 99% or more
In the same manner, CaaCuOs was combined with CaaCuOs for 10 hours at 950℃.It was confirmed by X-ray diffraction that a single-phase powder was obtained.Then, the obtained BaCuOa, Ca2CuOs and , Tl*Os, PbO, CuO and Ag with a purity of 99% or more
Weigh each of the powders in a○ so that they are in the prescribed ratio and mix them in a dry method.
This molded body was uniaxially pressurized at a pressure of 600 kg/cm'' in a mold of 600 kg/cm. Temperature changes in electrical resistance were measured from 300K to 77K at a measurement current of 10mA using the usual four-probe method with six electrodes attached.
), we measured the temperature change in magnetic susceptibility when cooling under an external magnetic field of 100 e. :． Tl:
The ratio of Ba: Ca: Cu was 1.2: 2:
The critical temperatures in the table are Roll, Rz●"s, L@I are the onset temperature storms of electrical resistance, respectively. Table 1 As shown in Table 1, +-.A critical temperature of 120K or more was obtained when the Ag addition amount was 0.1 to 30% by weight, and the sample was annealed at 910°C for 30 minutes when the addition amount was 1% by weight. When cooled to 4.2K, the magnetic susceptibility is -0.012e mu /
When the crystal structure was investigated by X-ray diffraction, T
It was removed from the two phases of 2BarcaaCusO- and metal Ag.Although it is extremely convenient from the viewpoint of stabilizing superconducting materials, which is a problem at the stage of practical application, we added Ag. The sample is more dense than the sample without the addition.Table 2 shows the ratio of Tl:Ba:Ca:Cu.
:2:2:3 and L The results are shown when the amount of Ag added was fixed at 1% by weight.

(Margin below) Table 2 As shown in Table 2, the amount X is O. 8 or more, a critical temperature of 120K or more is obtained, f:, x = 4.0
The crystal structure of a sample burned at 920°C for 120 minutes was investigated by X-ray diffraction.7fx TItBatCa*Cu
fQ, which is separated from the two phases of s O v and metal Ag,
Excess TI can be easily controlled by evaporation by increasing the firing temperature or by increasing the firing time; Table 3i; t. ．． The results of investigating the variation in data when Ag was added and when no Ag was added revealed that the addition of Ag was superior not only in terms of the square force characteristics but also in the reproducibility of the data. Deamo Table 3 (Hereafter blank) (Hereafter blank) Example 2 TlaOs, PbO, Sr's, C with a purity of 99% or more
a 02, CuO and AgzO powders were weighed in a predetermined ratio and mixed in a dry method.
Follow the same process until burning, and in Table 4, T I ++-+++tp b++S r2c
At anc u so 0v, x=0.5, z=1.2,
The results are shown when n = 2 and m = 3.

(The following is a blank space) Table 4 As shown in Table 4, the amount of Ag added is 0. A critical temperature of 120K or higher is obtained when the concentration is 1 to 30% by weight.
The crystal structure of a sample burned at 900°C for 30 minutes with an additive amount of 1% by weight was investigated by X-ray diffraction (T l s.sP
bi. s) S Excess TI from the two phases of raCa2Cusov and metallic Ag can be easily controlled by evaporation by increasing the sintering temperature or also by increasing the sintering time.

Table 5 shows the results when changing the ratio X of TI and Pb1; just L'I'l++-x+-+wM++Sr2
In Ca*Cu-0-, z=1.2, n=2,
m=3, and the amount of Ag added is 1% by weight.Table 5 As shown in Table 5, X is 0. 3 to 0, a critical temperature of 12OK or more is obtained, and the effect of the invention is in the range of circle 7.According to the present invention, by simply performing the burning command in an oxygen atmosphere, 1
It is possible to produce oxide superconducting materials with T0 of 20K or more with good reproducibility.Also, the material of the present invention is mainly composed of two phases of superconductor and metal Ag, and superconducting materials are a problem at the stage of practical application. Although it is an extremely convenient material from the viewpoint of stabilizing conductive materials,

Claims (2)

[Claims] (1) Chemical formula Tl_xBa_2Ca_nCu_mO_y
(However, Ag is 0 for 0.8≦x, 2≦n, 3≦m)
．． An oxide superconducting material containing 1 to 30% by weight. (2) Chemical formula Tl_(_1_-_x_)_・_zPb_
xSr_zCa_nCu_mO_y (0.3≦x≦0.
7, 1≦z, 2≦n, 3≦m), Ag from 0.1 to
An oxide superconducting material containing 30% by weight.