KR970007311B1 - Method of manufacturing mercury (Hg) -barium (Ba) -calcium (Ca) -copper (Cu) -oxygen (O) based high temperature superconductor - Google Patents

Abstract

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Description

Method of manufacturing mercury (Hg) -barium (Ba) -calcium (Ca) -copper (Cu) -oxygen (O) based high temperature superconductor

1 is a graph showing the superconductivity characteristics of the high temperature superconductor manufactured according to the present invention.

The present invention relates to a method for manufacturing a high temperature superconductor for use in electronic devices such as computers, geological exploration devices, medical devices and military exploration devices, more specifically Hg-Ba-Ca-Cu having a critical temperature of 125-135K. It relates to a method for producing a high temperature superconductor of -O-based.

The manufacture of superconductors with high critical temperatures is due to the easier and economical application of the excellent properties of superconductors. Since the refrigerant used in the conventional superconductor is expensive and difficult to handle, it is expected that the manufacture of the superconductor which can use the refrigerant which is cheap and easy to handle is excellent in economical efficiency and broad marketability.

Hg-Ba-Ca-Cu-O-based high temperature superconductors having a critical temperature of 125-135 K or more have been recently discovered, and most of the superconductors in this system are HgBa ₂ Ca _n-1 Cu _n O _{2n + 2 + x} compounds. Among them, the critical temperature of HgBa ₂ Ca ₂ Cu ₂ O _{8 + x} is the highest, and several other compounds coexist. If the compound is prepared by the high temperature-high pressure process of 850-950 ° C., a large volume ratio in the sample is formed of the HgBa ₂ Ca ₂ Cu ₃ O _{7 + x} compound.

Conventionally, a mass of a compound having a composition of Ba ₂ Ca ₂ Cu ₃ O ₇ and a mixture having a composition of HgBa ₂ Ca ₂ Cu ₃ O ₈ are placed in a crystal tube and heat-treated at 850-860 ° C. to allow mercury in the mixture to penetrate the compound. ₂ Ca ₂ Cu ₃ O _{8 + x} compounds have been prepared.

However, in order to form HgBa ₂ Ca ₂ Cu ₃ O _{7 + x} compound well, the high temperature process and the sintering time have to be long. In the case of the conventional method, both the compound and the mixture react strongly with the crystal tube at high temperature There is a problem to lower the characteristics of the superconductor.

In addition, in the conventional method, since HgBa ₂ Ca ₂ Cu ₃ O _{8 + x} compound has a compound phase with a very low activation temperature, mercury oxide reacts with them at a low temperature of about 500 ° C. to form impurities, thus HgBa ₂ Ca There is a problem that the uniformity of the ₂ Cu ₃ O _{8 + x} compound is reduced.

In addition, since the conventional method is a hot-press process, the equipment is complicated and expensive, and in the case of the compound produced in the high-temperature process, impurities such as BaCuO, CaCuO ₂ , and Ca ₂ CuO ₃ at grain boundaries Since the concentration is high, the conductivity is very bad, and there is a problem that the compound cracks in the process of reducing the pressure at high temperature and high pressure.

In the present invention, since the CaCuO _{2 + x} compound is separated from the HgBa ₂ CaCu ₂ O _{6 + x} compound, Hg-Ba-Ca-O which contains less impurities and easily converts into HgBa ₂ CaCu ₃ O _{8 + x} compound. It is an object of the present invention to provide a method for manufacturing a high temperature superconductor.

Another object of the present invention is that the compounds are separated from the quartz tube by using an alumina tube as the reaction tube so that the compound hardly reacts with the quartz tube, so that the temperature of the process can be further increased and the holding time during sintering can be increased. An object of the present invention is to provide a method for manufacturing a high temperature superconductor based on Hg-Ba-Ca-Cu-O. Hereinafter, this invention is demonstrated in detail.

The present invention is a method for producing a high temperature superconductor based on Hg-Ba-Ca-Cu-O, Ba ₂ CaCu ₂ O _{5 + x} compound and CaCuO _{2 + x} compound at a temperature of 800-920 ℃ by a conventional solid-phase reaction method Preparing a; The Ba ₂ CaCu ₂ O _{5 + x} compound and mercury oxide were mixed at a molecular ratio of 1: 1, and then reacted at a temperature of 800-820 ° C. and mercury vapor pressure of 100 atm or higher to prepare a HgBa ₂ CaCu ₂ O _{6 + x} compound. Doing; The HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound were mixed at a molecular ratio of 1: 0.5 to 1: 1, and then reacted at a temperature of 820-850 ° C. with mercury vapor pressure of 100 atm or higher to obtain HgBa ₂ Ca. Preparing a ₂ Cu ₃ O _{8 + x} compound; And heat-treating the HgBa ₂ Ca ₂ Cu ₃ O _{8 + x} compound while flowing oxygen at a temperature of 250-300 ° C. and 1 atm of Hg-Ba-Ca-Cu-O-based high temperature superconductor. It relates to a manufacturing method.

Hereinafter, the present invention will be described in more detail.

In order to manufacture Hg-Ba-Ca-Cu-O-based high-temperature superconductor according to the present invention, first, Ba oxide, Ca oxide, and Cu oxide are mixed in accordance with a desired composition, and then heat-treated at 800-920 ° C. by a conventional solid phase method. ₂ CaCu ₂ O _{5 + x} compound and CaCuO _{2 + x} compound are prepared.

Next, a Ba ₂ CaCu ₂ O _{5 + x} compound and a mercury oxide were mixed at a 1: 1 molecular ratio, and then reacted at a temperature of 800-820 ° C. and mercury vapor pressure of 100 atm or higher to prepare a HgBaCaCu ₂ O _{6 + x} compound. do.

Preferably, the Ba ₂ CaCu ₂ O _{5 + x} compound and mercury oxide are mixed in a 1: 1 molecular ratio, placed in an alumina (Al ₂ O ₃ ) tube, and then placed in the fertilization tube again, the internal pressure of the fertilization tube is about 10 mTorr, and the fertilization tube is sealed. After that, it was put in a stainless steel pipe together with silver powder, and the stainless steel pipe was put into an electric furnace and heated to 800-820 ° C. at about 200 ° C. per hour to maintain the temperature range and mercury vapor pressure over 100 atm for 10 hours. Next, the compound mass is prepared by cooling to room temperature at a cooling rate of about 80 ° C. per hour, which mass is mainly composed of HgBa ₂ CuO ₄ compound and HgBa ₂ CaCu ₂ O _{6 + x} compound, and CaHgO ₂ compound and Ba ₂ Cu ₃ O _{5 + x} compounds contain impurities. Preferred examples of the quartz tube include an inner diameter of 5 mm, a length of 50-70 mm, and a thickness of 2-2.5 mm.

When the reaction temperature is 800 ℃ or less, not only takes too much time to obtain the target phase compound, but it is difficult to obtain the target phase. When the reaction temperature is higher than 820 ℃, the compound reacts with the reaction tube (alumina tube, crystal tube, etc.). Since the desired phase compound is not obtained, the reaction temperature of the Ba ₂ CaCu ₂ O _{5 + x} compound and the mercury oxide is preferably limited to 800-820 ° C.

In addition, a more preferable mercury vapor pressure in the reaction of the Ba ₂ CaCu ₂ O _{5 + x} compound and the mercury oxide is 100-300 atmospheres.

Next, the HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound were mixed at a molecular ratio of 1: 0.5 to 1: 1, and then reacted at a temperature of 820-850 ° C. and mercury vapor pressure of 100 atm or higher to obtain HgBa. Prepare ₂ Ca ₂ Cu ₃ O _{8 + x} compounds.

Preferably, the HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound are placed in an alumina (Al ₂ O ₃ ) tube so that the molecular ratio is from 1: 0.5 to 1: 1, and the alumina tube is placed in a quartz tube. After sealing, it is put in a stainless steel tube with silver powder, and then put into an electric furnace and heated to 820-850 ° C. at about 200 ° C. per hour, and maintained at this temperature range and at a mercury vapor pressure of 100 atm or higher for about 10 hours, and then at 80 ° C. per hour. By cooling to room temperature to a degree, a compound mass is prepared, which is mainly composed of HgBa ₂ CaCu ₂ O _{6 + x} compound and HgBa ₂ Ca ₂ Cu ₃ O _{8 + x} compound, CaHgO ₂ compound and Ba ₂ Cu ₃ The O _{5 + x} compound contains impurities.

When the reaction temperature of the HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound is 820 ° C. or less, it takes too much time to obtain the compound of the desired phase, and it is difficult to obtain the desired phase, 850 ° C. In the above case, since the compound does not react with the reaction tube (alumina tube, crystal tube, etc.) to obtain a desired phase compound, the reaction temperature of the HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound is 820-850 ° C. It is preferable to limit to.

Next, the HgBa ₂ Ca ₂ CuO _{8 + x} compound is heated to 250-300 ° C., and heat treatment is performed while flowing oxygen at this temperature section and 1 atm. A high temperature superconductor is produced.

The heating rate during the heat treatment is preferably about 100 ℃ per hour.

Hg-Ba-Ca-Cu-O-based high temperature superconductor prepared according to the present invention has a critical temperature of 125-135K.

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

Example

Inventive Example

Ba ₂ CaCu ₂ O _{5 + x} (called Compound A) and CaCuO _{2 + x} (called Compound B) were prepared by a conventional solid phase reaction, and then A compound and mercury oxide were mixed at a molecular ratio of 1 to 1 to alumina ( Al ₂ O ₃ ) into the tube, and put it back into the fertilization tube to make the internal pressure of the fertilizer tube about 10mTorr and suture. This was put in a stainless steel tube together with silver powder, and the stainless steel tube was heated at 200 ° C. per hour to 800 ° C. for 10 hours to prepare a HgBa ₂ CaCu ₂ O _{6 + x} compound (called a C compound).

The mercury vapor pressure in the crystal tube was 100-300 atm, and the cooling rate was 80 ℃ per hour.

The C and B compounds are sprayed at a ratio of 1: 0.5 to 1: 1 (adjusting the mercury vapor pressure in the fertilization tube according to the molecular ratio), and then placed in an alumina (Al ₂ O ₃ ) tube and sealed again. Put this together with silver powder in the stainless steel pipe. This was put back in an electric furnace and heated to 200 ° C. per hour to 850 ° C. for 10 hours to prepare HgBa ₂ Ca ₂ Cu ₃ O _{8 + x} compound (referred to as D compound). At this time, the mercury vapor pressure in the crystal tube was 100-300 atm, the cooling rate was 80 ℃ per hour.

The compound was put back into an electric furnace and heated to 100 ° C. at 300 ° C. per hour, maintained for 20 hours while flowing oxygen at 1 atm, and cooled to prepare Hg-Ba-Ca-Cu-O-based high temperature superconductor.

As a result of measuring the superconductivity of the high temperature superconductor manufactured as described above, as shown in FIG. 1, the critical temperature was 125-135 K at normal pressure.

Comparative Example 1

The same as the invention example, but by adjusting the amount of the mercury-based compound inside the crystal tube to produce a high-temperature superconductor with a mercury vapor pressure of 40 atm inside the crystal tube, after measuring the superconductivity characteristics superconducting phenomenon at a critical temperature of 125-135K Did not appear.

Comparative Example 2

The same as the invention example, but by adjusting the amount of the mercury-based compound inside the crystal tube to produce a high-temperature superconductor with a mercury vapor pressure of 70 atm inside the crystal tube, after measuring the superconducting properties superconducting phenomenon at a critical temperature of 125-135K Did not appear.

As described above, in the present invention, the CaCuO _{2 + x} compound is separated from the HgBa ₂ CaCu ₂ O _{6 + x} compound, thereby containing less impurities and easily converting the compound into HgBa ₂ Ca ₂ Cu ₂ O _{8 + x} compound. By providing the Hg-Ba-Ca-Cu-O-based high-temperature superconductor manufacturing method, there is an effect that can ensure the reliability and accuracy in the superconductivity characteristics when applied to industrial fields.

In addition, the present invention is the effect of using the anlumina tube as the reaction tube is separated from the crystal tube so that the compound hardly reacts with the crystal tube, so that the temperature of the process can be further increased, and the holding time during sintering can be increased. There is.

Claims (2)

A method for producing a Hg-Ba-Ca-Cu-O-based high temperature superconductor, the method comprising: preparing a BaCaCu ₂ O _{5 + x} compound and a CaCuO _{2 + x} compound at a temperature of 800-920 ° C. by a conventional solid phase reaction method; The BaCaCu ₂ O _{5 + x} compound and mercury oxide were mixed at a molecular ratio of 1: 1, and then reacted at a temperature of 800-820 ° C. and mercury vapor pressure at 100-300 atmospheres to form a HgBa ₂ CaCu ₂ O _{6 + x} compound. Manufacturing step; The HgBa ₂ CaCu ₂ O _{6 + x} compound and the CaCuO _{2 + x} compound were mixed at a molecular ratio of 1: 0.5-1: 1, and then reacted under a mercury vapor pressure of 100-300 atm with a temperature of 820-850 ° C. Preparing a ₂ Ca ₂ Cu ₃ O _{8 + x} compound; And HgBa ₂ Ca ₂ Cu ₃ O _{8 + x} Hg-Ba-Ca-Cu-O-based system characterized in that it comprises a step of heat treatment while flowing oxygen at a temperature of 250-300 ℃ and 1 atmosphere condition Method for producing high temperature superconductor. The method according to claim 1, wherein the HgBa ₂ CaCu ₂ O _{6 + x} compound and HgBa ₂ Ca ₂ Cu | A method for producing a Hg-Ba-Ca-Cu-O-based high temperature superconductor, wherein the ₃ O _{8 + x} compound formation reaction is performed in an alumina tube inside a quartz tube charged into an electric furnace.