JPH0772086B2 - Method for producing thick film of Bi-Sr-Ca-Cu-O-based superconducting oxide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a thick film of crystal-oriented Bi—Sr—Ca—Cu—O-based superconducting oxide on a substrate.

The thick film is a film having a thickness of 10 μm or more.

[Prior Art] Since Bednorz and Muller reported high-temperature superconducting oxides of the La-Ba-Cu-O system (Phys.B64 (1986) 189), T _C
YB of (absolute temperature at which electric resistance becomes 0, hereinafter T _C ) is about 90K
Report of a-Cu-O superconducting oxide (Phys.Rew.Lett.58 (19
87) 908) The development competition for high-temperature superconducting oxides is extremely fierce.

Furthermore, recently Bi-Sr-Ca-Cu- O system from T _C to about 105K
A new high-temperature superconducting oxide that has the properties (J.Appl.Phys.27
(1988) L209). However, this Bi-Sr-Ca-Cu-
O system T _C in the superconducting oxide has two phases of oxide and oxides of 75K of 105K, or to how many crystallized the high T _C phase this Bi-Sr-Ca-Cu This is a problem of -O superconducting oxide. To solve this problem, Takano et al. Have proposed Bi-Sr-Ca-C.
reported that the ratio of the high T _C phase increases abruptly by replacing a portion of Bi of uO based superconducting oxide Pb (Jpn.J.Ap
pl.Phys.27 (1988) L1041).

On the other hand, a method of forming a thin film on a bulk material or a substrate formed by a sintering process has been actively researched for the superconducting oxide. The bulk material has a problem that the superconducting material is an oxide, so that it is difficult to form into a desired shape due to poor workability, and the J _C (critical current density, hereinafter referred to as J _C ) is low because of the large number of pores. Moreover, there is a problem that T _{C of the} thin film is lower than that of the bulk material. From these points of view, it has been desired to develop a product in which a thick film having a current value that can actually flow without lowering T _C is formed on the substrate.

The thin film and thick film have different uses.For thin films, superconducting devices using Josephson junctions such as NIS and SIS are the main, whereas thick films are macro, for example, circuits such as printed circuit boards or tapes. Can be considered.

As a method for forming a thin film on a substrate, Bi-Sr-Ca-Cu-O is used.
A method of printing and heat-treating a paste of superconducting oxides on the MgO single crystal (100) surface (Jpn.J.Appl.Phys.27 (1988)
However, T _C is about 80K.

In addition, there is a property that a Bi-Sr-Ca-Cu-O-based superconducting oxide is made amorphous by quenching. P
hys.27 (1988) L533) has been reported. However, since this method is not formed on the substrate, there is a problem that it is difficult to put it into practical use as it is.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a thick film of Bi-Sr-Ca-Cu-O-based superconducting oxide having a high T _{C and} having a crystallographic orientation.

[Means for Solving the Problems] The present invention provides a Bi-Sr-Ca-Cu-O system and optionally Cd or Pb.
Calcination, crushing, and melting of a powder containing oxides of the above are melted, rapidly solidified to produce an amorphous or thin piece containing amorphous material, and the thin piece is placed on a substrate at 800 ° C to 8 ° C.
It is characterized by heat treatment at 90 ° C.

[Operation] Hereinafter, the present invention will be described in detail. The superconducting oxide used in the present invention is easily Bi-Sr-Ca-Cu-O.
It is a superconducting oxide and contains Cd oxide. Bi-Sr-Ca-Cu- O based superconducting oxide Bi ₂ Sr as a high T _C phase
_{It is said that the 2} Ca ₂ Cu ₃ O _Y phase has a Bi ₂ Sr ₂ CaCu ₂ O _Y phase or a Bi ₄ Sr ₃ Ca ₃ Cu ₄ O _Y phase as a low T _C phase. Thus the Bi-Sr-Ca-Cu- O based superconducting oxide high T _C phase, the formulation of raw materials for low T _C phase coexists high T _C phase Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _Y
It is fired in accordance with the, T _C (on the electrical resistance begins to drop
set) fluctuates and T _C (end) at which electric resistance becomes 0 is 105K
With shifts to even more low-temperature side, there is a tendency that the temperature range is widened from T _C (on set) to T _C (end). As mentioned above, Bi
Is a sintered body in which a part of P is replaced with Pb, T _C (on set) 125K, T
The value of _C (end) 107K is obtained.

However, when a thick film obtained by amorphizing a superconducting oxide having the above composition is heat-treated on a MgO single crystal substrate, T _C decreases as shown by the curve (b) in FIG. 3 and the high T _C as described above.
Turned out not to get.

Inventors have high T _C based on this finding Bi-Sr-Ca-C
A method of forming a thick film of uO-based superconducting oxide on a substrate was investigated. As a result, we have found a method of producing a thin piece of Bi-Sr-Ca-Cu-O based superconducting oxide which is first made amorphous or containing amorphous by rapid solidification and then heat treating this thin piece on a substrate. That, Bi-Sr-Ca-Cu -O based superconducting oxide is a high-T _{C-phase Bi 2 Sr 2 Ca 2 Cu 3} O Y so that the Bi ₂ O _3, CaCo
Powders of ₃ , CuO, SrCO ₃ , PbO and CdO are blended, mixed well, and then calcined in air at 800 ° C. This is crushed and a sample is molded by CIP. It is desirable that this sample be melted as quickly as possible and rapidly solidified so that the composition does not change due to evaporation or the like. For example, a sample is formed into a rod shape by CIP, the tip of the rod is rapidly melted in an arc image furnace using a xenon or halogen lamp, and the dropped melt is rapidly solidified by rotating twin rollers or one roller.

The thus obtained amorphized or rapidly solidified thin piece containing amorphous is heat-treated on a substrate at 800 ° C to 890 ° C. The substrate may be either a single crystal of oxide such as MgO, SrTiO ₃ or ZrO ₂ , a metal such as Ag or Pt, or a semiconductor such as Si. As shown in Fig. 1, this amorphized thin piece (Fig. 1 (a) produces a high TC phase at around 800 ° _C (Fig. 1 (d)). Is not desirable because it melts and cannot retain its shape.

Similarly, in the Bi ₂ Sr ₂ Ca _1.8 Cd _0.2 Cu ₃ O _Y system, as shown in Fig. 2 (a), in the case where most of the flakes containing CaO crystals are amorphized, the high T _C phase is higher than 800 ° C. Was observed (Fig. 2 (b)).

As a result of SEM observation, crystals of these phases are all oriented. By this method, a superconducting oxide phase in which crystals are oriented can be obtained on the substrate. Bi ₂ S obtained in this way
_{r 2 Ca 2-X Cd X} Cu 3 O Y superconducting T _C of the oxide thick film x = 0.2 at 84
With K, x = 0.4, 87K was obtained.

[Example] Bi ₂ O ₃ , CaCO ₃ , CuO, SrCO ₃ , PbO and CdO were added to Bi _0.7 Pb _0.3 SrCa.
Cu _1.8 O _Y , Bi ₂ Sr ₂ Ca _2-X Cd _X Cu ₃ O _Y , x = 0,0.2,0.4,0.8,1.
The ingredients were blended so as to be 0, 1.4, 2.0, mixed with methanol in an agate mortar for 4 hours, and calcined in air at 800 ° C for 12 hours. This is crushed and the diameter is 2.5mm and the length is 150mm by CIP.
Was molded into a rod shape. The tip of this rod was melted in an arc image furnace using a xenon lamp and twin rollers (2000rp
m) Ultra-quenched to obtain a thin sample with a thickness of about 20 μm. This sample is placed on the (100) cleavage plane of MgO single crystal and the temperature is 800 ℃ ～ 890
A thick film was formed by heat treatment at ℃. An example of the result is shown in FIG. As is clear from this figure,
Bi ₂ Sr ₂ Ca _2-X Cd _X Cu ₃ O _Y system T _C (on set) 100K or more, x
= 0.2, T _C (end) 84K, x = 0.4, 87K. The range of x, which has a high T _C and good superconductivity, is 0.1 to 0.8.
Then, when X exceeded 1.0, it became an insulating phase.

[Effects of the Invention] A thin piece of Bi-Sr-Ca-Cu-O-based superconducting oxide is made amorphous by rapid solidification, and this thin piece is heat-treated on a substrate to obtain the thickness of the crystal-oriented superconducting oxide. It became possible to obtain a film, and the possibility of developing a superconductor element capable of passing a large current was obtained.

[Brief description of drawings]

Figures 1 and 2 show the X-ray diffraction results before and after heat treatment of Bi-Sr-Ca-Cu-O based superconducting oxides with different compositions, and Figure 3 shows Bi ₂ Sr ₂
Ca _2-X Cd _X Cu ₃ O _Y at x = 0.2 and Bi _0.7 Pb _0.3 SrCa
It is a figure showing change of electric resistance of Cu _1.8 O _Y.

Claims (1)

[Claims] 1. A thin piece containing an amorphous or amorphous material by melting, rapidly quenching and solidifying an object obtained by calcining, crushing, and molding a powder containing a Bi-Sr-Ca-Cu-O system and a Cd oxide. Then, the thin piece is heat-treated at 800 ° C. to 890 ° C. on the substrate, and the Bi ₂ Sr ₂ Ca _{2 -X} Cd _X Cu ₃ O _Y system (where x = 0.2
~ 0.4) A method for manufacturing a superconducting oxide thick film.