JPH0755826B2 - Superconductor - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to superconductors. In particular, it relates to a compound thin film superconductor.

Conventional technology As high-temperature superconductors, niobium nitride (NbN) and germanium niobium (Nb ₃ Ge) were known as A15 type binary compounds, but the superconducting transition temperature of these materials is at most
It was 24 ° K. On the other hand, perovskite-based ternary compounds are expected to have even higher transition temperatures, and Y-Ba-Cu-O-based high-temperature superconductors have been proposed [MKWu et al., Physical Review Latters] Vol.58, No.
9,908-910 (1987)] Furthermore, it was recently proposed that the Bi-Sr-Ca-Cu-O system is a higher temperature superconductor.

Although the details of the superconducting mechanism of Bi-Sr-Ca-Cu-O-based materials are not clear, the transition temperature may be higher than the liquid nitrogen temperature. More promising characteristics are expected.

However, Bi-Sr-Ca-Cu-O-based materials can only be formed in the form of ceramic powder or blocks, because they can be formed only in the process of sintering with the current technology. On the other hand, when this kind of material is put to practical use, thinning or linearization is strongly demanded, but in the conventional technology, 900 to 100
A high processing temperature of 0 ° C is required, and it is extremely difficult to put them into practical use.

The present inventors have partially replaced the enzyme component of this type of material with another element such as sulfur, and when a thinning method such as a sputtering method is used, the processing temperature is lowered, and the thin film high-temperature superconductor has a low temperature. It was discovered that they were formed, and based on this, they invented a new superconductor structure.

Means for Solving the Problems The superconductor of the present invention is Bi-Sr-Ca-Cu-O, further characterized in that a part of the oxygen component is replaced with at least one of sulfur, selenium, tellurium, and polonium. I am trying.

Action The superconductor according to the present invention is not an oxide ceramic, but a composite ceremix composed of, for example, an oxide and a sulfide, and the present invention realizes that the processing temperature is lowered in the composite.

That is, the present inventors have determined that the oxygen element of this type of oxide ceramic is an element other than oxygen of the VIb group, such as sulfur (S), selenium (Se), tellurium (Te), polonium (P
It has been discovered that similar superconducting properties can be obtained even if some of them are replaced with o). In this case, especially the oxygen substitution amount is 50% or less, that is, In that case, a particularly stable superconducting property was obtained. Although details of the reason are not clear, it shows that the base structure of the Bi-Sr-Ca-Cu-O-based oxide ceramics was stably formed when the oxygen substitution amount was 50% or less. That is, 50%
When oxygen is replaced as described above, the perovskite structure or the oxygen octahedral structure forming the perovskite structure is not stably formed. In this case, what is particularly noteworthy is that when oxygen is replaced by sulfur, selenium, tellurium, polonium, etc., the crystallization temperature becomes low, and it becomes possible to lower the formation temperature of this kind of material. It was In this case, the substitution of oxygen does not necessarily have to be a single element, and the present inventors have also found that two or more of sulfur, selenium, tellurium, and polonium, such as sulfur and selenium and sulfur and tellurium, may be used. confirmed.

Examples Hereinafter, more specific examples will be shown in order to deepen the understanding of the content of the present invention.

(Specific Example) Sintered Bi using the sapphire single crystal R surface as the substrate 11
- (SrCa) by high-frequency planar magnetron sputtering of ₂ -Cu ₂ -O _x S _y target was deposited coating 12. In this case, the pressure of Ar gas is 0.5 Pa, the sputtering power is 150 W,
The sputtering time was 6 hours, the film thickness was 5 μm, and the substrate temperature was 350 ° C. The formed film was further heat-treated and slowly cooled at 500 ° C. for 2 hours in a sulfur atmosphere. As described above, the room temperature resistivity of the film formed at the relatively low processing temperature is 10 mΩc.
m, superconducting transition temperature 90 ° K.

In this case, a processing temperature of 500 ° C. was required without adding sulfur.

In particular, the superconductor according to the present invention is more convenient when the superconductor is made into a thin film. That is, thinning decomposes the material of the superconductor into ultrafine particles in the atomic state and then deposits it on the substrate, so that the composition of the formed superconductor is essentially more uniform than that of the conventional sintered body. Moreover, it can be formed at a low temperature. Therefore, it can be realized with a very high-precision superconductor.

Further, when the superconductor of the present invention is formed as a thin film, the above-mentioned various substrates and crystal planes can be used, and integration can be similarly performed.

Effects of the Invention As described above, the present invention can lower the crystallization temperature by partially substituting oxygen, can obtain an advantageous method in the production of a superconductor, integration with a device such as Si or GaAs, It is extremely convenient for element materials of various superconducting devices such as Josephson devices. In particular, the transition temperature of this type of compound superconductor may reach room temperature, the range of conventional practical use is wide, and the industrial value of the present invention is high.

[Brief description of drawings]

 FIG. 1 is a block diagram of a superconductor substrate according to an embodiment of the present invention. 11 ... Substrate, 12 ... Ternary compound coating.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kumiko Hirochi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Shinichiro Hatta 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Rika Yamao 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 63-319245 (JP, A) JP 64-52321 (JP, A) JP 64-100818 (JP, A)

Claims (2)

[Claims] 1. A superconducting material, characterized in that the main component is an oxide of Bi, Sr, Ca, Cu-O, and a part of oxygen is replaced by at least one of sulfur, selenium, tellurium and polonium. body. 2. The ratio of sulfur, selenium, tellurium, and the polonium component to the oxygen component is The superconductor according to claim 1, wherein