JPH01257162A - Porcelain composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to resistor ceramic compositions, particularly barium oxide (Ba
O), strontium oxide (SrO), and thulium oxide (
Regarding the resistive ceramic composition composed of the components Ttn 203 ) and copper oxide (CaO), the resistivity at room temperature (ρ
3°. ), the resistivity (ρCo) from room temperature to the onset critical temperature (TcO) is small, and the resistivity is zero below the liquid nitrogen temperature.

Conventional technology In recent years, Bedno', /V tsu (Bednorz)
and Muller, Ba-La-C
The possibility of high-temperature superconductor materials in the u-0 system was discovered in 1986.
Zeitschrift Fear Fitzk (Zeit)
scriftfiir Physik) Ba4
Published in Volume 189.

In this report, the onset critical temperature (TcO) at which the resistivity (ρ) of the material begins to rapidly decrease is around 30 degrees absolute, but the offset critical temperature (TC) 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 high density, a high temperature Tc, and a smaller ρ in the temperature range from room temperature to Tco. .

The present invention was made to improve the above-mentioned drawbacks, and the sintered material has a high density, a low resistivity from room temperature to the on-cent critical temperature, and superconducting properties at the temperature of inexpensive liquid nitrogen. The present invention provides a novel ceramic composition having a high Tc.

The only way to solve the problem is to make it double! Jt (Bad) and strontium oxide (S)
rO), thulium oxide (Tm2O3), and copper oxide (CuO
), the compositional formula is Tm(Ba
1-. 5rx) When expressed as 2Cu3O7, its component composition is expressed in mole fraction. x≦0.75.

The composition described in item 1 of "Operation" is a resistive porcelain with excellent resistance from room temperature to the onset critical temperature, and also becomes a superconducting porcelain in liquid nitrogen.

The starting materials for the examples include chemically highly purified B a COs (99
-5% or more) + S r C0-5 (99% or more)
, Tm203 (99,9%) and Cu0 (99,5%
(above) was weighed out to the specified composition, and then milled in a polyethylene ball mill equipped with an agate ball.
Mixed time-wise. This mixture was taken out of a ball mill and dried, and then the powder was placed in an alumina crucible and calcined in air at a temperature of 900° C. for 5 hours. The obtained calcined product was crushed using a crusher equipped with an agate mortar and an agate pestle. After grinding, 5% by weight of propyl alcohol was added as a binder to the powder to make it homogeneous, and the powder was then passed through a 32 sieve sieve for granulation. Shida. The sized powder was put into a rectangular rod or pot using a mold and a hydraulic press at a molding pressure of 900 ky/cd, and then heated in oxygen at 900 °C.
It was held and fired at a temperature within the range of ~11oo'C for 6 hours 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.

For the rectangular bar sample, 60 insulated copper wires with a diameter of Oi2fl were used.
The change in inductance due to temperature change (from gi body nitrogen temperature to room temperature) was measured at a frequency of 10 kHz using an LCR meter. The inductance values of these samples at room temperature were 4 to 6 μH. Inductance decreases rapidly near liquid nitrogen temperature (3%)
For the sample, 4-terminal electrodes were attached with a width of 1 On+ on both end faces perpendicular to the long side of the rectangular rod and on the long side using gold evaporation or baked silver, and the resistance under a constant current (10 mA) was measured. The temperature change (from liquid nitrogen temperature to room temperature) was measured.

The experimental results are shown in the table. In addition, 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.

As is clear from the table, the porcelain composition substituted with Sr within the scope of the present invention has a high sintering density, can reduce the resistivity in the range from room temperature to the onset critical temperature, and A material with a high offset critical temperature Tc can be obtained below this 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, Sr○
When the maximum substitution value x becomes 0.75 or more, the sintered density decreases and the resistivity at room temperature and up to the on-cent critical temperature becomes too high, making it impossible to obtain superconducting properties at the surface nitrogen temperature. Further, when x=O, the sintered density is low and the resistivity of the chamber is still large, 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 isolation reactors and linear motor trains when cooled with liquid nitrogen, ultra-high-speed computer elements such as Josephson elements, and high-power It is suitable for application in a wide range of fields such as power transmission lines and superconducting printed circuits, and can be used to make inexpensive, high-performance electronic devices and circuit parts, making it extremely valuable industrially.

Claims (1)

[Claims] Barium oxide (BaO) and strontium oxide (SrO
), thulium oxide (Tm_2O_3) and copper oxide (CuO
), whose compositional formula is Tm(Ba_1_−_xSr
_x) A porcelain composition characterized in that, when expressed as _2Cu_3O_7, its component composition is in the range of 0<x≦0.75 in terms of molar fraction.