PROCESS FOR PRODUCING CHEVREL COMPOUNDS

Abstract: A process for producing Chevrel compounds, which comprises baking a mixture of metal sulfide, a metal molybde­ num and molybdenum sulfide reduced pressure or in an inert gas stream containing a reducing gas, or braking a mix­ ture of metal sulfide and molybdenum sulfide in an inert gas stream containing a reducing gas. This process enables syn­ thesis of Chevrel compounds inexpensively on a large scale repeatedly using the same reaction vessel without complicated steps as is different from conventional processes.

Description: This invention relates to a manufacturing process of chevrel compounds whose electric resistance in a temperature range of liquid helium becomes almost zero and which can be used as a material for superconductor utilizable in the fields of high efficiency power storage, generation of intense magnetic field and high efficiency power transmission or as an electrode material for electrochemical element. Since chevrel compounds have a critical temperature higher than a temperature of liquid helium and have a very high critical magnetic field, many studies have been made. Moreover, certain chevrel compounds such as, for example, copper chevrel compounds wherein the metal element can be chemically or electrochemically released from or received in the compound without destroying the skelatal structure of Mo₆S₈ of the compound have been expected for application as an electrode material of electrochemical element. In a conventional process of manufacturing chevrel compounds, it was usual that powders of various metal elements, metallic molybdenum powder and sulfur powder were mixed after milling, and the mixture was placed in a quartz glass tube and sealed under reduced pressure, and sintered at 400°C for 12 hours, then at 600°C for 12 hours and finally at 1000°C for 24 hours. For example, the EP-A 0 171918 describes a process for producing a PbMo₆S₈ type compound semiconductor comprising the heat-treatment under vacuum of a pellet formed from the base materials by molding In this process, the starting materials contain sulfur which is apt to react with most metals and are sintered after placing in a reaction tube and sealing the tube under reduced pressure, so that it is necessary to use as the reactor tube a quartz glass tube which is stable against sulfur and can be worked as desired. After the sintering, it is essential to open the quartz glass reaction tube in order to withdraw the resultant product, making it difficult to use the quartz glass reaction tube several times. In addition, if large amounts of the product are prepared in one batch, sulfur will be gasified during the course of temperature rise. When the pressure of the resultant gas becomes too high, the quartz glass reaction tube is broken. Thus, the production process is complicated and involves a problem in the industrial production of the compound. The object of the present invention is to provide a manufacturing process for chevrel compounds which is simple and is adapted for mass-production. The above object of the invention is achieved by a process which comprises mixing a sulfide of metal (which metal is at least one element selected from Li, Na, Mg, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Pd, Ag, Cd, In, Sn, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), molybdenum sulfide and optionally metallic molybdenum, and sintering the mixture in a stream of an inert gas (argon, helium or nitrogen gas) containing a reductive gas. Fig. 1 is a schematic illustrative view of a sintering apparatus for manufacturing chevrel compounds under reduced pressure; Fig. 2 is a powder X-ray diffraction pattern of a chevrel compound; and Fig. 3 is a schematic illustrative view of a sintering apparatus for manufacturing chevrel compounds in an inert gas stream containing hydrogen. The present invention is described by way of examples. (Example 1) A copper chevrel compound, Cu₂Mo₆S₈ (100 g) was prepared in the following manner. Cuprous sulfide powder (16.95 g), metallic molybdenum powder (25.00 g) and molybdenum disulfide powder (59.35 g ) were weighed and mixed in a glass ball mill for 3 hours, after which the mixed powder was charged into a quartz glass reaction tube, followed by sintering by the use of the following sintering apparatus under reduced pressure at 700°C for 30 hours and then at 1000°C for 40 hours to obtain copper chebrel compound, Cu₂Mo₆S₈. The sintering apparatus for manufacturing the chevrel compound under reduced pressure is shown in Fig. 1. In Fig. 1, indicated at 1 is a starting material, at 2 is a quartz glass reaction tube into which the starting material is charged, at 3 is an electric furnace, at 4 is a thermocouple, at 5 is a trap and at 6 is an oil rotary vacuum pump. The thus obtained copper chevrel compound, Cu₂Mo₆S₈, was subjected to powder X-ray diffraction analysis, revealing that it consisted substantially of a single phase. In Fig. 2, there is shown a powder X-ray diffraction pattern. With regard to the superconductivity of the copper chevrel compound, Cu₂Mo₆S₈, the critical temperature was about 10 K. (Example 2) A nickel chevrel compound, Ni₂Mo₆S₈ (100 g) was prepared. The production procedure is described below. In the same manner as in Example 1, nickel sulfide powder (19.12 g), metallic molybdenum (30.31 g) and molybdenum disulfide (50.57 g) were weighed and mixed in a glass ball mill for 3 hours, after which the mixed powder was charged into a quartz glass reaction tube and sintered by the use of a sintering apparatus as used in Example 1 under reduced pressure at 700°C for 30 hours and then at 1000°C for 40 hours to obtain the nickel chevrel compound of the formula, Ni₂Mo₆S₈. The thus obtained nickel chevrel compound, Ni₂Mo₆S₈, was subjected to powder X-ray diffraction analysis, with the result that a diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass tube was obtained. (Example 3) A lead chevrel compound, PbMo 6.2 S₈, (100 g) was prepared. The production procedure is described below. In the same manner as in Example 1, lead sulfide powder (22.60 g), metallic molybdenum powder (24.47 g) and molybdenum disulfide powder (52.93 g) were weighed and mixed by the use of a glass ball mill, after which the mixed powder was charged into a quartz glass reaction tube, followed by sintering by the use of a sintering apparatus as used in Example 1 at 700°C for 30 hours and then at 1000°C for 40 hours to obtain the lead chevrel compound, PbMo 6.2 S₈. The thus obtained lead chevrel compound, PbMo 6.2 S₈, was subjected to powder X-ray diffraction analysis, revealing an X-ray diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass reaction tube. The superconductive characteristic of the lead chevrel compound, PbMo 6.2 S₈, was such that the critical temperature was about 12 K. (Example 4) A silver chevrel compound, AgMo₆S₈, (100 g) was prepared. The production procedure is described below. In the same manner as in Example 1, silver sulfide powder (13.18 g), metallic molybdenum powder (22.96 g) and molybdenum disulfide powder (63.66 g) were weighed and mixed by the use of a glass ball mill, after which the mixed powder was charged into a quartz glass reaction tube, followed by sintering by the use of a sintering apparatus of the type described below in a nitrogen gas stream containing 1% of hydrogen as a reducing gas at 700°C for 30 hours and then at 1000°C for 40 hours to obtain the silver chevrel compound, AgMo₆S₈. In Fig. 3, there is shown a schematic view of a sintering apparatus for the manufacture in an inert gas stream containing a reductive gas. In Fig. 3, indicated at 7 is a gas flow rate controlling device, at 8 is a quartz glass reaction tube, at 9 is an electric furnace, at 10 is a thermocouple, and at 11 is a nitrogen gas bomb containing 1% of hydrogen. The thus obtained silver chevrel compound, AgMo₆S₈, was subjected to powder X-ray diffraction analysis, revealing an X-ray diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass reaction tube. The superconductive characteristic of the lead chevrel compound, AgMo₆S₈, was such that the critical temperature was about 7 K. (Example 5) A tin chevrel compound, SnMo₅S₆, (100 g) was prepared. The production procedure is described below. Stannous sulfide powder (19.06 g) and molybdenum sulfide powder (101.21 g) were weighed and mixed by the use of a glass ball mill, after which the mixed powder was charged into a quartz glass reaction tube, followed by sintering by the use of a sintering apparatus as used in Example 5 in a nitrogen gas stream containing 50% of hydrogen at 500°C for 30 hours and then at 800°C for 40 hours to obtain the tin chevrel compound, SnMo₅S₆. The thus obtained tin chevrel compound, SnMo₅S₆, was subjected to powder X-ray diffraction analysis, revealing an X-ray diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass reaction tube. The superconductive characteristic of the tin chevrel compound, SnMo₅S₆, was such that the critical temperature was about 12 K. (Example 6) A copper chevrel compound, Cu₄Mo₆S₈, (100 g) was prepared. The production procedure is described below. A hydrogen sulfide gas was passed into an aqueous solution dissolving copper acetate, (CH₃CO₂)4Cu₂ · 2H₂O, thereby causing copper sulfide to precipitate. The resultant copper sulfide was filtered and washed, after which it was dried and mixed with a small amount of sulfur by the use of a glass ball mill for 3 hours, followed by treatment in a stream of hydrogen at 400°C for 10 hours to obtain copper sulfide. This copper sulfide, metallic molybdenum powder (26.49 g) and molybdenum disulfide powder (44.20 g) were weighed and mixed by the use of a glass ball mill, after which the mixed powder was charged into a quartz glass reaction tube, followed by sintering by the use of a sintering apparatus as used in Example 5 in a stream of nitrogen gas containing 1% of hydrogen as a reducing gas at 700°C for 30 hours and then at 1000°C for 40 hours to obtain the copper chevrel compound, Cu₄Mo₆S₈. The thus obtained copper chevrel compound, Cu₄Mo₆S₈, was subjected to powder X-ray diffraction analysis, revealing an X-ray diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass reaction tube. (Example 7) An iron chevrel compound, FeMo₅S₆, (100 g) was prepared. The production procedure is described below. Ammonium sulfide was added to an aqueous solution of ferrous chloride, FeCl₂ · 4H₂O, (27.31 g) thereby obtaining iron sulfide. Next, molybdenum oxide, MoO₃, (98.87 g) was dissolved in an aqueous ammonia solution, after which hydrogen sulfide was passed to obtain molybdenum sulfide. Thus obtained iron sulfide and molybdenum sulfide were mixed by the use of a glass ball mill for 3 hours. The mixed powder was charged into a quartz glass reaction tube and sintered by the use of a sintering apparatus as used in Example 5 in a nitrogen gas stream containing 50% of hydrogen at 500°C for 30 hours and then at 800°C for 40 hours, thereby obtaining the iron chevrel compound, FeMo₅S₆. The thus obtained iron chevrel compound, FeMo₅S₆, was subjected to powder X-ray diffraction analysis, revealing an X-ray diffraction pattern similar to that of a product prepared after sealing a conventional quartz glass reaction tube. The iron chevrel compound prepared according to the above procedure was found to be finer in size than those prepared from conventional starting materials such as iron sulfide, molybdenum sulfide and metallic molybdenum. In the above examples, copper, nickel, lead, silver, tin and iron sulfides were used as metal sulfides, it will be possible to prepare chevrel compounds by similar procedures using other sulfides of metals such as Li, Na, Mg, Ca, Sc, Cr, Mn, Co, Zn, Sr, Y, Pd, Cd, In, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. As described in detail hereinabove, chevrel compounds can be prepared by mixing metal sulfide powder, molybdenum sulfide powder and optionally metallic molybdenum powder, and sintering the mixture in a stream of inert gas containing a reductive gas, so that no complicated step is necessary as in prior art processes. In addition, the reactor can be re-used a desired number of times and it is possible to produce the compounds inexpensively in large amounts. LIST OF REFERENCE NUMERALS IN THE DRAWINGS 1 starting material 2,8 quartz glass reaction tube 3,9 electric furnace 4,10 thermocouple 5 trap 6 oil rotary vacuum pump 7 gas flow rate controller 11 gas bomb

Claims: A process for manufacturing Chevrel compounds characterized by sintering a mixture of a sulfide of a metal which metal is at least one element selected from the group of Li, Na, Mg, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Pd, Ag, Cd, In, Sn, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and molybdenum sulfide in a stream of an inert gas containing a reductive gas. A process according to claim 1 wherein metallic molybdenum is additionally contained in the mixture. A process according to claim 1 or 2 wherein the metal sulfide is prepared from a solution conaining a metal salt wherein the metal is at least one element selected from the group of Li, Na, Mg, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Pd, Ag, Cd, In, Sn, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu and the molybdenum sulfide is one which is prepared from a solution containing a molybdenum salt.

Inventors: KONDO SHIGEO, YAMAMURA YASUHARU, KONDO, SHIGEO, YAMAMURA, YASUHARU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1988
Main classification: C01G39
IPC codes: C01G53, H01L39, C01G39, C01B17, C01G49, H01M4