JPH02188464A - porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a porcelain compsn. having low resistance at room temp., low resistivity in the temp. range from room temp. to the onset critical temp. and superconducting characteristics at the temp. of liq. nitrogen by incorporating BiO1.5, SrO, CaO, CuO and PbF2 in a specified molar ratio. CONSTITUTION:28.4-14.0mol% BiO1.5 is wet-mixed with 28.6-20.0mol% SrO, 22.2-14.3mol% CaO, 40.0-28.6mol% CuO and 6.7-0.1mol% PbF2 in a highly purified state and this mixture is dried, calcined at 780-800 deg.C in the air for about 12hr and crushed. The resulting powder is pulverized, mixed with a binder, molded and sintered at 840-875 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a resistive ceramic composition, particularly vinyl oxide: x (
Bib1, 6) SrO
) Regarding the resistor ceramic composition composed of the components of calcium oxide (Cab), copper oxide (CuO), and lead fluoride (PbF2), it not only has a small resistivity (ρ3°) at room temperature, but also has a low resistivity at room temperature. The object of the present invention is to provide a superconducting porcelain having a small resistivity (ρC○) from 100 to an onset critical temperature (TcO), and further exhibiting a resistivity of zero below the liquid nitrogen temperature.

Prior Art Recently, the possibility of high-temperature superconductor materials in the B a-L a-Cu-0 system was discovered by Bednorz and M'aller in 1986,
furPhygik) B, Volume 64, Page 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 temperature, but the zero resistance critical temperature (TcO) 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 wood materials are used as low-resistivity conductive materials in the range from room temperature to onset critical temperatures, materials with higher density and lower resistivity are required to minimize power losses. Ru.

Problems to be Solved by the Invention In order to solve these problems, it is desired to develop a material with a higher density and a lower resistivity in the temperature range from room temperature to TcQ and at higher temperatures. ing.

The present invention has been made in order to improve the above-mentioned drawbacks.The sintered material has a low resistivity from room temperature to the onset critical temperature, and also exhibits superconducting properties at the temperature of inexpensive liquid nitrogen. The present invention provides a novel porcelain composition with high porcelain composition.

Means to solve the problem Bismuth oxide (Bib, 6), strontium oxide (SrO), calcium oxide (Cab), and copper oxide (Cu)
O) and lead fluoride (PbF2).Saller composition: B io Ka28.4-14.01.
5 mol%, SrO is 28.6-20. 'O-E: )
v%, CaO 22.2-14.3 moyV%, C
uO is 40.0-28.6 mol%, PbF2 is 6.7-28.6 mol%
The range is 0.1 mol%.

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.

Starting materials for the examples include chemically highly purified B tol, 5(99,
9%), 5rCO3 (more than 99%), CaCO5 (
99% or more), CuO (99.5% or more) and P
bF2 (99%) was weighed to have a predetermined composition, and mixed with water for 17 hours in a polyethylene ball mill equipped with an agate ball. After the mixture was taken out of the ball mill and dried, the powder was placed in an alumina crucible and calcined in air at a temperature of 780 to 800 tons for 12 hours. The obtained calcined product was crushed using a crusher equipped with an agate mortar and an agate pestle. After pulverization, 5% by weight of propyl alcohol was added as a binder to the powder to make it homogeneous, and the powder was sized through a 32-mesh sieve. The sized powder was molded into a rectangular bar (18 x 4 x approximately 3 fl thick
) and a disk sample (diameter 10 mm, thickness approximately 2 mm) was molded. After placing the molded body in a high-purity alumina pot,
96 at a temperature within the range of 840-876°C in air
The product was fired for a certain period of time to obtain resistor porcelain having the composition shown in the table. The weight and dimensions of the disk samples were measured and the density was calculated. A rectangular rod sample was wound with an insulated copper wire of 0.12 mm in diameter 60 times, and a frequency of 10 KHz was measured using an LCR meter.
The change in inductance due to temperature change (from GI body nitrogen temperature to room temperature) was measured. The inductance values of these samples at room temperature were 3 to 5 μH.

Inductance decreases rapidly near liquid nitrogen temperature (
%~%) For the sample, four-terminal electrodes were attached by gold vapor deposition or baked silver with a width of 10 ff on both end faces perpendicular to the long sides of the rectangular bar and on the long sides, and - constant current (10 mA) was applied. The temperature change in resistance (from liquid nitrogen temperature to room temperature) was measured under 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.

As is clear from the table, the ceramic composition in which a portion of BiO is replaced with PbF2 within the scope of the present invention can reduce the resistivity in the range from room temperature to the onset critical temperature of 1.6 A material with a high zero resistance critical temperature (TC) can be obtained 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 for limiting the composition range of the present invention, PbF
The amount of substitution of BiO by is 7 mol% or more2
1+6, the sintered density decreases and the resistivity at room temperature and up to the onset critical temperature increases υ, making it impossible to obtain the effects of the present invention. Moreover, the amount of substitution by PbF2 is 0.
If it is less than 1 mol %, the sintered density will be low and the resistivity at room temperature will be high, so it is excluded from the scope of the present invention. Additionally, if the compositions of pismanu oxide, strontium oxide, and copper oxide are outside the scope of the claims, superconducting properties in which the electrical resistance is zero at temperatures below the liquid nitrogen temperature cannot be obtained, so they are outside the scope of the present invention. removed.

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 short-motor cars when cooled with liquid nitrogen, ultra-high-speed computer elements such as Josephson elements, and high-power transmission devices. It is suitable for application in a wide range of fields such as electric wires and superconducting printed circuits, and can be used to make inexpensive, high-performance electronic devices and circuit parts, and has significant industrial value.

Claims (1)

[Claims] It consists of bismuth oxide (BiO_1_._5), strontium oxide (SrO), calcium oxide (CaO), copper oxide (CuO), and lead fluoride (PbF_2), and when its component composition is expressed in molar percentage, BiO_1_. ＿
5 is 28.4 to 14.0 mol%, SrO is 28.6 to 2
0.0 mol%, CaO 22.2-14.3 mol%, C
uO is 40.0 to 28.6 mol%, PbF_2 is 6.7
A porcelain composition characterized in that it is in the range of 0.1 mol %.