JPH01175793A - Manufacture of superconductor thick film - Google Patents

Abstract

PURPOSE:To prevent superconduction transformation temperature of a superconductor from being lowered by causing the superconductor to react with a substrate simultaneously with sintering by screen-printing on the partially stabilized zirconia substrate a paste yielded by blending a rare earth-barium-copper oxide with an organic vehicle, and calcining the substrate in an acidic environment at a particular temperature for a particular time interval. CONSTITUTION:A paste, which is yielded by blending a superconductor comprising a rare earth-barium-copper oxide with an organic vehicle, is screen-printed into a desired geometrical shape on a zirconia substrate, which is partially stabilized, and calcined in an acidic atmosphere at a temperature of 950 deg.C or more or 1000 deg.C or less for 10 minutes. For example, Y2O3, BaCO3, and CuO are weighed into a molar ratio of 1:2:3 and wet-mixed using a ball mill, and calcined in air at about 900 deg.C and again ground using a ball mill. Resulting powder is blended in an organic solvent with an organic binder into a paste. The paste is screen-printed on the zirconia substrate, which is stabilized by yttria. Further, the binder is removed from the paste in an acidic or neutral atmosphere, and the paste is sintered in an acidic atmosphere at 980 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing a ceramic thick film printed body using a superconducting oxide.

(Conventional technology) Conventionally, Pb, Nb, Nb3Ge have been used as superconducting materials.
Elemental metals, alloys, and intermetallic compounds were known. Devices that take advantage of their superconductivity have been created by processing these materials, mainly by forming them into thin films or cotton materials. Since the superconducting transition temperatures of these materials were all below 23.2, cooling with liquid helium was necessary. For this reason, only a limited number of devices have been applied using superconductors. In recent years, La-Ba-C
Among u-0 series, (La1-xBax)2CuO4 has 0.
The composition with 075≦X≦0.1 has Tc of 30K and Y
Among the -Ba-Cu-0 systems, it has been reported one after another that the composition of YBa2Cu30y has a Tc of around 90. Furthermore, the position of Y in YBa2Cu30y is changed to lanthanum, neodymium, samarium, among other rare earth elements.
It has also been reported that even if it is replaced with europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, or thulium, or even if two or more of these elements are mixed, the Tc remains approximately the same at about 90. . Since the Tc of these superconductors including the Y-Ba-Cu-0 system has become higher than the boiling point (77K) of liquid nitrogen, there are increasing expectations for their use as practical materials.

The discovery of this oxide that exhibits superconductivity above the boiling point of liquid nitrogen will allow the cooling device to be small and simple, allowing the creation of low-cost devices using superconductivity that have not been used in the past. The possibility has emerged. Therefore, it is expected that thick films using printing technology, which can be produced with cheaper equipment than thin films and wires that require large and expensive equipment, will be applied to inexpensive superconducting devices.

However, there have been few reports of attempts to create wiring patterns or devices such as 5QUIDs by thick film printing of this oxide. Currently, several cases have been reported in which thick superconductor films have been created using the screen printing method, but since a reaction occurs between the substrate used and the superconductor oxide, stable superconductor thick films cannot be achieved. It has not yet been achieved.

(Problems to be Solved by the Invention) The present invention provides that when heat treatment is performed to sinter a superconductor thick film formed by a screen printing method, a reaction occurs with the substrate at the same time as sintering, and the superconductor thick film is heated. An object of the present invention is to provide a method for manufacturing a superconducting thick film that solves the problem of lowering the superconducting transition temperature.

(Means for Solving the Problems) The present invention involves creating a paste by kneading rare earth-barium-copper-based oxides with an organic vehicle, and printing the paste onto a partially stabilized zirconia substrate using a screen printing method to make it superconducting. The present invention is a method for producing a superconductor thick film, characterized in that the superconductor thick film is formed and the firing time is 10 minutes or less at a temperature of 950° C. to 1000° C. in an oxidizing atmosphere.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example) In the present invention, a superconductor paste was created as follows. Yttrium oxide (Y2O2), barium carbonate (BaCOa), and cupric oxide (Cub) with a purity of 99.9% or more are used as starting materials, and the molar ratio is 1:2:
It was weighed so that it was 3. These were wet mixed using a ball mill, then calcined in air at a temperature of 880°C to 920°C, and re-pulverized using a hole mill.The powder was kneaded with an organic binder and an organic solvent to form a paste. In preparing the paste, appropriate amounts of an ethylcellulose-based binder and terpineol as an organic solvent were added and kneaded to form a paste. The resulting paste was printed onto an yttria-stabilized zirconia substrate using a screen. Next, the printed material on the substrate was debindered in an oxidizing or neutral atmosphere, and further fired at 9506C, 980°G, and 1000°C in an oxidizing atmosphere. The temperature reduction rate from the firing temperature to room temperature was controlled to be 100° C. or less per hour. This is because in order for the yttrium-barium-copper oxide to exhibit superconductivity, it is necessary to reduce oxygen defects, so the temperature drop is slowed down and oxygen is introduced into the conductor oxide. Here, the baking time is θ minutes, 5 minutes.

Firing was performed for 10 minutes, 15 minutes, 30 minutes, and 60 minutes.

As a result of measuring the electrical characteristics of the superconductor thick films produced in this manner, it was found that in the range of Examples, some of them transitioned to a superconducting state at about 90 ℃ and the electrical resistance became 0. The superconducting transition temperature (0
The results are summarized in Table 1.

When firing at a firing temperature of 980° C. for 30 minutes or more, or at 1000° C. for 15 minutes or more, the printed material turned green and became an insulator. As a result of identifying this using powder X-ray diffraction, it was found that it had changed into Y2BaCuO5. Furthermore, the cross-sectional morphology of these printed bodies and substrates was observed using a scanning electron microscope (SEM), and the elemental distribution at the interface between the printed bodies and the substrate was analyzed using an energy dispersive X-ray analyzer (EDX). It was found that BaZrO3 was generated at the interface inside the substrate. From these analysis results, the oxide superconductor composition YBa2Cu
3O7 readily reacts with Yttria-stabilized zirconia at the temperature at which sintering occurs, producing BaZrO3, and the lack of Ba ions in the print makes the print Y2BaCuO.
It is thought that it has changed into 5. From these results, it has been found that sintering a superconductor thick film can be achieved by shortening the firing time while controlling the reaction between the printed body and the substrate.

Similar effects were also confirmed with one or more types of oxide superconductors in which the rare earth element is not yttrium but lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holosium, erbium, thulium, ytterbium, lutetium, etc.

(Effects of the Invention) As is clear from the examples, the superconductor thick film of the present invention has an electrical resistance of 0 near 90°C. According to the present invention, devices can be produced at a lower cost than conventionally used superconductor thin films, and wiring substrates and wiring boards on which Josephson elements, superconducting transistors, LSIs with superconducting wiring, etc. can be mounted, etc. This is expected to be applied to 5QUID.

Table 1

Claims (2)

[Claims] (1) A paste made by kneading a superconductor consisting of a rare earth-barium-copper oxide with an organic vehicle is formed into the desired shape on a partially stabilized zirconia substrate by screen printing, and the paste is formed at 950°C or higher in an oxidizing atmosphere. A method for producing a superconductor thick film, comprising firing at a temperature of 1000° C. or lower and for a firing time of 10 minutes or less. (2) A patent claim characterized in that the rare earth element is one of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, or a mixture of two or more of these elements. A method for producing a superconductor thick film according to item 1.