JPH0226859A - Ceramic composition - Google Patents

Abstract

PURPOSE:To provide a ceramic compsn. having small resistivity in a range from room temp. to onset critical temp., having high critical temp., and exhibiting superconducting characteristic at the b.p. of liquid N2 by constituting the compsn. of BaO, SrO, Yb2O3 and CuO regulated to specified molar ratios. CONSTITUTION:BaCO3, SrCO3, Yb2O3 and CuO each having high purity are weighed so as to obtain a compsn. expressed by the formula, wherein 0<x<=0.75. The materials are mixed in a ball mill, etc., and calcined provisionally after drying, and then pulverized. After adding a binder (e.g., propyl alcohol) to the obtd. powder, the product is compression-molded and obtd. molded body is calcined in O2 at 900-1100 deg.C. Thus, a ceramic compsn. to be used for resistor is prepd. A superconducting magnet or a Josephson element, etc., capable of producing a strong magnetic field useful for linear motor mar is prepd. by cooling the ceramic compsn. with liquid N2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to resistor ceramic compositions, particularly barium oxide (Ba
Regarding the resistor ceramic composition composed of the following components: O), strontium oxide (SrO), ytterbium oxide (Ybz05), and copper oxide (Cub), the resistivity at room temperature (ρ
The present invention provides a superconducting porcelain that not only has a small resistivity (ρ...) from room temperature to the onset critical temperature (Tco), but also has a resistivity of zero below the liquid nitrogen temperature. be.

Conventional technologyIn recent years, Bθdnorz, Tomuller
(Miiller) Yoshi, Ba -La -0u-
The possibility of high-temperature superconductor materials in the
hriftr;ir Physik) Be published in volume 4, page 189.

In this report, the onset critical temperature (Tco) at which the resistivity (ρ) of the material begins to rapidly decrease is around the absolute temperature of 30 degrees, but the offset critical temperature (Ta) at which the resistivity becomes zero
The absolute temperature of this material is as low as 13 degrees Celsius, and this material requires expensive liquid helium as a coolant, which has been a major obstacle to its practical application. Furthermore, when this material is used as a conductive material with low resistance in the range from room temperature to the onset critical temperature, it is desirable to use a material with high density and low resistivity in order to minimize power loss.

Problems to be Solved by the Invention In order to solve these problems, it is desired to develop a material that has a higher density and has a higher temperature Tc+ and a smaller ρ in the temperature range from room temperature to Tco.

The present invention has been made to improve the above-mentioned drawbacks.The sintered material has a high density, a low resistivity from room temperature to the onset critical temperature, and superconductivity at the temperature of inexpensive liquid nitrogen. The present invention provides a novel porcelain composition with high properties exhibiting properties.Means for solving the problem
), ytterbium oxide (Yb203), and copper oxide (Cu
b), whose compositional formula is Yb (
When expressed as Ba1-X Srx )2 Cu5Q7, the component composition is O (X≦0.75) in terms of mole fraction.

Operation The above composition is an excellent resistor porcelain from room temperature to the onset critical temperature, and also becomes a superconductor porcelain in liquid nitrogen.

Examples of starting materials include chemically high-purity BaCO3 (99.5% or higher), F3rGO5 (99% or higher), YbzO3 (
99,91) and Cub (99.6% or more) were weighed to give a predetermined composition and mixed with water for 17 hours in a polyethylene ball mill equipped with an agate pole. After taking out the mixture from the ball mill and drying it, the powder was placed in an aluminum crucible and heated to 900°C in the air.
It was calcined at a temperature of 'C for 5 hours. The obtained calcined product was pulverized using a pickling machine equipped with an agate mortar and an agate pestle. 5 parts by weight of propyl alcohol was added as a binder to the pulverized powder to make it homogeneous, and the mixture was sized through a 32-mesh sieve. The sized powder is molded into a rectangular bar (1
A disk sample (10 mm diameter x about 2+ nm thick) was molded. The molded body was placed in a high-purity alumina pot and then heated to a temperature of 900 to 11 in oxygen.
It was held at a temperature within the range of 0° C. for 6 hours and fired to obtain a resistor ceramic having the composition shown in the table.

The weight and dimensions of the disk samples were measured and the density was calculated. An insulated copper wire with a diameter of 012 mm was wound 60 times around a rectangular bar sample, and changes in inductance due to temperature changes (from liquid nitrogen temperature to room temperature) were measured using an LCR meter at a frequency of 10 kHz. The inductance values of these samples at room temperature were 4 to 5 μH. For samples whose inductance decreases rapidly near the liquid nitrogen temperature (14~), add 10 mm on both end faces perpendicular to the long sides of the rectangular rod and on the long sides.
Four-terminal electrodes were attached with a width of 100 mm apart using a gold vapor deposition or baked silver method, and the temperature change in resistance (from liquid nitrogen temperature to room temperature) under a constant current (10 m) was measured. The experimental results are shown in the table. Note that the samples marked with * in the table are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention.

(Left below) As is clear from the table, the porcelain compositions in which Sr is substituted by ゛ within the scope of the present invention have a high sintered density and a low resistivity in the range from room temperature to the onset critical temperature. It is possible to obtain a material having a high offset critical temperature Tc below the liquid nitrogen temperature. Therefore, by using the ceramic composition of the present invention, superconducting properties exhibiting zero electrical resistance can be easily obtained using liquid nitrogen, which is inexpensive and abundantly available, as a coolant.

To explain the reason why the composition range of the present invention is limited, SrO
If the substitution amount X exceeds 075, the sintered density decreases and the resistivity increases at room temperature and up to the onset critical temperature, making it impossible to obtain superconducting properties at liquid nitrogen temperatures. Further, when X=O, the sintered density is low and the resistivity at room temperature is high, so it is excluded from the scope of the present invention.

Effects of the Invention The porcelain composition of the present invention has superconducting properties at the temperature of liquid nitrogen by using resource-rich and inexpensive liquid nitrogen as a coolant without using expensive liquid helium or hydrogen. is obtained. Therefore, the porcelain composition of the present invention can be used in superconducting magnets that can produce strong magnetic fields for nuclear fusion reactors and linear motor cars when cooled with liquid nitrogen, ultra-high-speed computer elements such as Josephine elements, and high-power power transmission lines. It is suitable for application in a wide range of fields such as superconducting printed circuits and superconducting printed circuits, and can be used to make inexpensive, high-performance electronic devices and circuit components, making it extremely valuable industrially.

Claims (1)

[Claims] It consists of barium oxide, strontium oxide, ytterbium oxide, and copper oxide, and its composition formula is Yb (Ba_1_-
A porcelain composition characterized in that, when expressed as _xSr_x)_2Cu_3O_7, the component composition is in the range of 0<x≦0.75 in terms of molar fraction.