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• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
  • C04B35/4504—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing rare earth oxides
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/01—Manufacture or treatment
  • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/01—Manufacture or treatment
  • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
  • H10N60/0296—Processes for depositing or forming superconductor layers
  • H10N60/0408—Processes for depositing or forming superconductor layers by sputtering
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/80—Constructional details
  • H10N60/85—Superconducting active materials
  • H10N60/855—Ceramic materials
  • H10N60/857—Ceramic materials comprising copper oxide

Definitions

• the present invention relates to a superconductor utilizing superconductivity and a method for manufacturing it.
• Nb alloys such as Nb 3 Ge, Nb 3 Sn and the like are most frequently used. These Nb alloys, however, have a critical temperature of about 20K, so that they have a drawback that they cannot be used unless they are cooled by liquid helium.
• compounds in Ba-La-Cu-O system are known as a material having a relatively high critical temperature.
• Fig. 1 shows a temperature dependence of resistivity in a superconductor of Ba-La-Cu-O system (see Z. Phys. B; J. G. Bednorz and K. A. Muller 64, pp. 189-193, 1986).
• the critical temperature is 35K and the critical magnetic field is 60T.
• the critical temperature and the upper critical magnetic field in the superconductor of Ba-La-Cu-O system are as low as 35K and 60T, respectively, so that this system does not exhibit the superconducting state when it is cooled with inexpensive liquid nitrogen. Furthermore, such a system has a problem that the operation becomes unstable when it is cooled with liquid hydrogen or liquid neon, because the differences between the critical temperature and the boiling points of these coolants are too small.
• an object of the present invention is to solve the aforementioned problems and to provide a superconductor having a high critical temperature.
• Another object of the present invention is to provide a method of manufacturing a superconductor with a high critical temperature by easy control of its compositions.
• a superconductor comprises: an oxide having a composition formula of L x M 2-x CuO 4-y , wherein L is one or more elements in Group IIA in Periodic Table except Ra, M is one or more elements in Group III in Periodic Table except actinoid elements and T1, and 0 ⁇ x ⁇ 2 and 0 ⁇ y ⁇ 2.
• L in the composition formula may be one of Be, Mg, Ca, Sr and Ba, and M in the composition formula may be one of Sc, Y, B and Al.
• M in the composition formula may be La, and L may be (Sr 1- z A z ), in which A may be one of Ca and 3a and 0 ⁇ z ⁇ 1.
• L in the composition formula may be Sr, and M may be La.
• a superconductor comprises: an oxide having a composition formula of
• L x M 1- x CuO 3-y wherein L is one or more elements in Group IIA in Periodic Table except Ra, M is one or more elements in Group III in Periodic Table except actinoid element and T1, and 0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 1.5.
• L in the composition formula may be one of
• M in the composition formula may be one of Sc, Y, B and A1.
• M in the composition formula may be La, and L may be (Sr 1-z A z ), in which A may be one of Ca and Ba and 0 ⁇ z ⁇ 1.
• L in the composition formula may be Sr, and M may be La.
• M in the composition formula may be Y, and L may be
• each of D and E may be a different element selected from the group consisting of Ca, Sr and Ba, and 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1.5 and 0.3 ⁇ z ⁇ 0.7.
• a method of manufacturing a superconductor composed of an oxide containing copper and plural elements comprises the steps of: adding an acid to a mixed aqueous nitrate solution of copper and the plural elements to coprecipitate oxides of copper and the plural elements; sintering the resulting coprecipitates to obtain coprecipitated oxides; and oxidizing the coprecipitated oxides.
• the sintering may be carried out at a temperature within a range of 910-950°C and the oxidizing may be carried out at a temperature within a range of 910-950oC in an oxygen gas atmosphere.
• a method of manufacturing a superconductor composed ot an oxide containing copper and plural elements comprises the steps of: sintering a mixed powder of a compound of copper and the compounds of the prural elements to obtain sintered compounds; and oxidizing the sintered compounds.
• the sintering may be carried out at a temperature within a range of 890-910°C and the oxidizing may be carried out at a temperature within a range of 890-910°C in an oxygen gas atmosphere.
• the mixed powder may be powder of oxides of the plural elements or carbonates of the plural elements, or a mixture of the powder of the oxides and the powder of the carbonates.
• the mixed powder may be a mixture of SrCO 3 , BaCO 3 and Y 2 O 3 .
• a method of manufacturing a superconductor composed of an oxide containing copper and plural elements comprises the steps of: simultaneously sintering and oxidizing a mixed powder of a compound of copper and compounds of the plural elements.
• the simultaneous sintering and oxidizing steps may be carried out at a temperature within a range of 910-950°C.
• the mixed powder may be powder of oxides of the plural elements or carbonates of the plural elements, or a mixture of the powder of the oxides and the powder of the carbonates.
• the mixed powder may be a mixture of SrC ⁇ 3, BaC ⁇ 3 and Y 2 O 3 .
• the superconductor may have a composition formula of L x M 1- x CuO 3-y , in which M may be Y, L may be (D z E 1- z ), each of D and E may be a different element of Ca, Sr and Ba, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1.5 and 0.3 ⁇ z ⁇ 0.7, and the sintering step may be carried out at a temperature within a range of 930-1100°C, after calcining the mixed powder at a temperature within a range of 895-915°C.
• a method of manufacturing a superconductor composed of an oxide containing copper and plural elements comprises the steps of: mixing powder of a compound of copper with powder of a compound of at least one element of the plural elements; subjecting the resulting mixed powder to a solid phase reaction to form a first intermediate; mixing powder of a compound of copper with a powder of compounds of the remaining elements of the plural elements; subjecting the resulting mixed powder to a solid phase reaction to form a second intermediate; mixing the first intermediate with the second intermediate; and subjecting the resulting mixture to a solid phase reaction.
• the solid phase reaction may be carried out at a temperature within a range of 800-900°C.
• the compound powder may be an oxide powder or a carbonate powder.
• Fig. 1 is a graph showing a relation between resistivity and temperature in the conventional superconductor
• Fig. 2 is a graph showing a relation between critical temperature and composition in a first embodiment of the superconductor of Ba xY1- x CuO 3-y system according to the present invention
• Fig. 3 illustrates an X-ray diffraction pattern of the first embodiment of the present invention
• Fig. 4 is a graph showing a relation between resistivity and temperature in the first embodiment of the present invention.
• Fig. 5 is a graph showing a temperature dependence of an upper critical magnetic field in various superconductors
• Figs. 6 and 7 are graphs showing a relation between critical temperature and compositions in a second embodiment of superconductor according to the present invention, respectively;
• Fig. 8 is a graph showing a relation between resistivity and temperature in the superconductor of (Sr 1-z Ba z ) x La 2-x CuO 4-y system;
• Fig. 9 is a graph showing a relation between resistivity and temperature in the superconductor of (Sr 1-z Ca z ) x La 2-x CuO 4-y system;
• Figs. 10 and 11 are graphs showing a temperature dependence of an upper critical magnetic field in various superconductors, respectively;
• Fig. 12 is a graph showing a relation between critical temperature and composition in a third embodiment of Sr x La 2-x CuO 4-y system according to the present invention.
• Fig. 13 is an X-ray diffraction pattern of the third embodiment of the present invention.
• Fig. 14 is a graph showing a relation between resistivity and temperature in the third embodiment of the present invention.
• Fig. 15 is a graph showing a temperature dependence of an upper critical magnetic field in various superconductors
• Fig. 16 is a graph showing a relation between critical temperature and composition in a fourth embodiment of (Sr z Ba 1-z ) 2 YCu 3 O 9-3y system according to the present invention
• Fig. 17 is an X-ray diffraction pattern of the fourth embodiment of the present invention.
• Fig. 18 is a graph showing a relation between resistivity and temperature in the fourth embodiment of the present invention.
• Fig. 19 is an X-ray diffraction pattern of Ba x Y 1-x CuO 3-y system obtained by a fifth embodiment according to the present invention where an intermediate process is employed.
• the superconductor according to the present invention is maufactured by either one of coprecipitation process, powder process and intermediate process.
• coprecipitation and powder processes an amount of oxygen is adjusted while powder is sintered.
• Nitrate of each Ba, Y and Cu is weighed so as to provide a predetermined molar ratio of Ba/Y/Cu and dissloved in water. After the pH adjustment of the resulting aqueous nitrates solution, oxalic acid is added to coprec ipi tate oxide of each of Ba , Y and
• the dried coprecipitates are calcined at about 900oC, for example, 880-910°C.
• the sintered body is annealed at about 930°C, for example, 910-950oC in an oxygen gas atmosphere under about 1 atmospheric pressure (optimum pressure is dependent upon the composition).
• Nitrate of each Sr, La and Cu is weighed so as to provide a predetermined molar ratio of Sr/La/Cu and dissolved in water. After the pH adjustment of the resulting aqueous nitrates solution, oxalic acid is added to coprecipitate oxide of each Sr, La and Cu, and then the coprecipitates are dried.
• the dried coprecipitates are calcined at about 900°C, for example, 800-910°C.
• the calcined precipitates are pulverized into granules, which are pressed and sintered at about 900°C, for example, 800-910°C.
• the sintered body is annealed at 850-900°C in an oxygen gas atmosphere under a pressure of
• Ba, Y and Cu are mixed so as to provide a predetermined molar ratio of Ba/Y/Cu and calcined at about 900°C, for example, 880-910°C.
• the calcined mixture is pulverized into granules, which are pressed, sintered at about 930°C, for example, 910-950°C in an oxygen gas atmosphere and cooled in a furnace.
• Cu are mixed so as to provide a predetermined molar ratio of Sr/La/Cu and calcined at about 900°C, for example, 890-910°C.
• the calcined mixture is pulverized into granules, which are pressed and sintered at about 900°C, for example, 890-910°C.
• the sintered body is annealed at 850-900°C in an oxygen gas atmosphere under a pressure of 0.05-10 4 Torr (optimum pressure is dependent upon the composition).
• a mixed powder of SrCO 3 , BaCO 3 , Y 2 O 3 and CuO is calcined at about 900°C so as to provide a predetermined molar ratio of Sr/Ba/Y/Cu.
• the calcining temperature may be within a range of 895-905°C.
• the intermediate process has advantages that the reaction temperature is low, that the reaction time is short and that the control of the composition is easy.
• each of these three processes is applicable to all of superconductors according to the present invention.
• Fig. 2 shows a relation between composition and critical temperature in a first embodiment of the superconductor according to the present invention.
• an abscissa indicates a value of x in Ba x Y 1-x CuO 3-y system produced by the powder process, and an ordinate indicates a critical temperature Tc.
• Ba 2/3 Y 1/3 CuO 3-y has the same X-ray diffraction pattern as in oxygen-deficient perovskite (Ba 3 La 3 Cu 6 O 14+y ).
• Fig. 4 shows a relation between temperature and resistivity in the Ba x Y 1-x CuO 3-y system.
• curve 4A was obtained by plotting measured values of
• Tc is a starting temperature of the superconducting transition.
• critical temperature of the superconductor used herein means the starting temperature Tc of the superconducting transition.
• the critical temperature was 120K in Ba 0.5 Y 0.5 CuO 3-y , 125K in Ba 2/3 Y 1/3 CuO 3-y, and 123K in Ba 0.6 Y 0.4 CuO 3-y .
• curves other than curve 5A were obtained by plotting measured values of the conventional superconductors other than Ba x Y 1-x CuO 3-y system.
• the superconductor according to the present invention is high in the upper magnetic field and holds a high magnetic filed even at a temperature exceeding a liquid helium temperature.
• the first embodiment has been described with respect to the properties of the Ba x Y 1-x CuO 3-y system obtained by the powder process, this system can be manufactured by the coprecipitation process or the intermediate process. Even in the latter case, there is no substantial difference in the properties.
• a high cr i tical temperature and a high cr i tical magnetic field can be obtained in superconductors other than Ba x Y 2-x CuO 4-y . That is, superconductors represented by composition formula of L x M 2-x CuO 4-y , wherein L is one of element of Ba, Sr, Ca, Mg and Be, and M is one element of Y, Sc, Al and B, have a high critical temperature and a high critical magnetic field.
• Figs. 6 and 7 show a relation between composition and critical temperature in a second embodiment of the superconductor according to the present invention, respectively.
• an abscissa indicates a value of z in (Sr 1-z Ba z ) x La 2-x CuO 4-y system obtained by the powder process, and an ordinate indicates a critical temperature Tc.
• Fig. 6 an abscissa indicates a value of z in (Sr 1-z Ba z ) x La 2-x CuO 4-y system obtained by the powder process, and an ordinate indicates a critical temperature Tc.
• an abscissa indicates a value of z in (Sr 1-z Ca z ) x La 2-x CuO 4-y system obtained by the powder process, and an ordinate indicates a critical temperature Tc.
• the critical temperature Tc changed from 54K to 35K or from 54K to 18K.
• Fig. 8 shows a relation between resistivity and temperature in the (Sr 1-z Ba z ) x La 2-x CuO 4-y system.
• Fig. 9 shows a relation between resistivity and temperature in the (Sr 1-z Ca z ) x La 2-x CuO 4-y system.
• curve 9A is the same as curve 8C in Fig. 8 and curves 9B and 9C were obtained by plotting measured values of materials obtained by replacing Ba in curves 8A and 8B of Fig. 8 with Ca.
• Tc is a starting temperature of the superconducting transition
• T QM. is a middle temperature of the superconducting transition
• Tee is an end temperature of the superconducting transition.
• the critical temperature Tc was 54.0K in Sr 1.0 La 1.0 CuO 4-y , 53.0K in Sr 0 . 9 Ba 0.1 La 1. 0 CuO 4-y , 52.5K in
• Figs. 10 and 11 show a temperature dependence of an upper critical magnetic field in various superconductors, respectively.
• the superconductors other than (Sr 1-z Ba z ) x La 2-x CuO 4-y and (Sr 1-z Ca z ) x La 2-x CuO 4-y systems are the conventional superconductors.
• the superconductors according to the present invention had an upper critical magnetic field as high as 114-130T and held a high magnetic field even at a temperature exceeding the liquid hydrogen temperature.
• the present invention has been described with respect to the properties of (Sr 1-z Ba z ) x La 2-x CuO 4-y and (Sr 1-z Ca z ) x La 2-x CuO 4- y systems obtained by the powder process, there is no substantial difference in the properties, even when these systems are manufactured by the coprecipitation or intermediate process.
• a high critical temperature and a high critical magnetic field similar to those in the above case can be obtained even in (Sr 1-z Ba z ) x La 1-x CuO 3-y and (Sr 1-z Ca z ) x La 1-x CuO 3-y systems.
• Fig. 12 shows a relation between composition and critical temperature in a third embodiment of the superconductor according to the present invention.
• an abscissa indicates a value of x in Sr x La 2-x CuO 4-y system obtained by the powder process, and an ordinate indicates a critical temperature Tc. Even when the value of x changed, the critical temperature Tc was stable and was at approximately 54K.
• this system was SrLaCuO 4-y and had the same X-ray diffraction pattern as in La 2 CuO 4-y system, since the ionic radius of Sr is approximately equal to that of La.
• the fundamental structure of the X-ray diffraction pattern was K 2 NiF 4 structure, so that even when the value of y was arbitrarily determined, the X-ray diffraction pattern was not basically changed.
• peak O shows a peak of ortho-La 2 CuO 4 and peak C shows a peak of cubic-perovskite.
• an upper curve shows an X-ray diffraction pattern before the annealing
• a lower curve shows an X-ray diffraction pattern after the annealing.
• Fig. 14 shows a relation between resistivity and temperature in the Sr x La 2-x CuO 4-y system.
• a difference between curves 14B and 14C was caused by the difference between the samples.
• the critical temperature Tc of the Sr 1.0 La 1.0 CuO 4-y system was 54.0K, while the two samples of Sr 0.8 La 1.2 CuO 4-y system have critical temperatures of 42.3K and 42.0K, respectively.
• Fig. 15 shows a temperature dependence of an upper critical magnetic field in various superconductors.
• the superconductors other than the Sr x La 2-x CuO 4-y system were the conventional superconductors.
• the superconductor according to the present invention had a high upper critical magnetic field and held a high critical magnetic field even at a temperature exceeding the liquid helium temperature.
• a high critical temperature and a high critical magnetic field can be obtained even in Sr x La 1-x CuO 3-y system.
• Fig. 16 shows a relation between composition and critical temperature in a fourth embodiment of the superconductor according to the present invention.
• the superconductor of the fourth embodiment was (Sr z Ba 1-z ) x Y 1-x CuO 3-y system manufactured by the powder process.
• mixed powders of SrCO 3 , BaCO 3 , Y 2 O 3 and CuO were calcined at about 900°C and pulverized into granules and pressed and sintered at 930-1100°C in an oxygen atmosphere and cooled in a furnace.
• the resistivity started decreasing at 342K (69°C), and became below the measuring limit of 10 -8 ⁇ cm at 337K (64°C) or less to exhibit superconducting state. That is, Tc was 342K (69°C).
• the calcining temperature in the fourth embodiment was 920-1000°C, preferably 930-980° C .
• the sinter ing temperature was 980-1100°C, preferably 980-1030°C.
• the superconductivity at room temperature in the fourth embodiment according to the present invention was not necessarily realized by the oxygen-deficient perovskite structure as shown in the X-ray diffraction pattern in Fig. 17. That is, there is the possibility that the superconductivity at room temperature is realized by an unclear phase slightly incorporated into this system.
• a peak D indicates an oxygen-deficient perovskite.
• the intermediate process has advantages that the reaction temperature is low and the reaction time is short. Further, the composition can easily be controlled, so that it is ensured that a desired material is obtained. Moreover, this process is not influenced by an ion size, so that it is also ensured that a desired material is obtained. Further, while the above described the embodiment in the case of the Ba x Y 1-x CuO 3-y system, it is clear that the similar effect can be obtained in Ba x Y 2-x CuO 4-y system.
• Ca, Sr or Ba is used as an element of Group IIA
• La, Sc or Y is used as an element of Group III.
• the present invention is widely applicable to oxide superconductors containing Group IIA element.
• Group III element and copper are radioactive elements, so that they are not favorable as an element constituting superconductor.
• the critical temperature of at least 54K, possibly 134K or more and the upper critical magnetic field of at least 78T, possibly 240T or more, which have never been achieved in the conventional superconductors, can be realized. Therefore, the present invention is applicable to various purposes including superconducting machines and equipment cooled with liquid hydrogen or liquid nitrogen, which have never been achieved by the conventional techniques.

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