CN1038719A - The preparation method of superconductor - Google Patents
The preparation method of superconductor Download PDFInfo
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- CN1038719A CN1038719A CN89103432A CN89103432A CN1038719A CN 1038719 A CN1038719 A CN 1038719A CN 89103432 A CN89103432 A CN 89103432A CN 89103432 A CN89103432 A CN 89103432A CN 1038719 A CN1038719 A CN 1038719A
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Abstract
A kind of preparation method who is better than the oxide superconductor of conventional melting method.Prepare raw material with at least a composition of selecting or the polycrystalline that Y-M-Cu is oxide based oxide based from La-M-Cu, the material that is lower than CuO with fusing point dissolves above-mentioned raw material as flux, by the monocrystalline of above-mentioned saturated flux solution growth composite oxides.Can obtain size suitable monocrystalline that does not have lattice disorder and internal strain substantially and monocrystal thin films in this way.
Description
The present invention relates to a kind of preparation method of superconductor.Specifically, the present invention relates to a kind of preparation method of oxide superconductor.
At " Z.Physik.Discussed B-Condended Mattes64,189-193(1986) " and have perovskite crystal structure or have and the similar K of perovskite structure
2NiF
4The oxide superconducting materials of crystal structure, described structure is Ba
xLa
5-
xCu
5O
5(3-y)(wherein x=1 or 0.75, y＞0).Except that above-mentioned material, in having the oxide superconducting materials of perovskite crystal structure, SrTiO
3And BaPb
1-xBi
xO
3In " physics weekly, VOl.163, NO.2.11,380-390(1967) " and " Applied Physics, 22,205-212(1980) ", came into question respectively.
Therefore, expected once except these materials that also can have the oxide that has above-mentioned crystal structure and show superconducting property, these materials were considered to reach into the useful materials of superconductive device.But the critical temperature Tc of oxide superconducting materials with perovskite crystal structure is at Ba
xLa
5-x-Cu
5O
5(3-y)The low 35K that reaches under the situation of (wherein x=0.75, y＞0), and when temperature during above this temperature, material does not present superconductivity.
Similarly, in " physics weekly, 26,408-410(1987) ", a kind of oxide superconductor with high superconduction critical temperature has been discussed also, and promptly (Sr, La)
2CuO
4
In addition, to have the superconductor of the critical temperature Tc that exceeds liquid nitrogen temperature (77K) be known to the oxide based conduct of a kind of Y-Ba-Cu.
All above-mentioned superconductors have the isomery that utilizes perovskite structure and the structure that obtains, this structure quite stable.Specifically, (Sr, La)
2CuO
4Has K
2NiF
4Structure has more complicated structure, i.e. an anoxic perovskite structure and Y-Ba-Cu is oxide based.A
3B
2O
7, A
4B
3O
10, A
5B
4O
13And A
6B
5O
16Structure is considered to further complicated structure.In general, the crystal structure of material is complicated more, and it is also difficult more to produce material.So the degree of difficulty of producing above-mentioned material is pressed the order increase of above-mentioned material.This has just produced a problem, promptly obtain the order increase of the degree of difficulty of homogeneous material by above-mentioned material, and superconducting critical current density reduces in proper order by this.In general, oxide superconductor (is characterized in that having the CuO that is similar to above-mentioned material
6Octahedra) superconduction critical temperature, complicated more and have higher two-dimemsional number (being that these interplanar interactions reduce) Shi Yuegao when crystal structure when the plane that the C axle is defined as normal.This is because the increase of two-dimemsional number (two dimensionality) causes that a axle shortens and makes that the distance between the Cu atom and O atom reduces in this plane.This causes that just Cu atom 3d track and the interorbital overlapping degree of O atom 2p increase, and cause the raising of current-carrying electronic conductivity in this plane thus.So the superconductor that includes above-mentioned material has high superconduction critical temperature.But these superconductors have complicated crystal structure, and its problem has caused producing difficulty.
In general, to have the CuO that is similar to above-mentioned material
6Octahedron or CuO
5Pentahedron is in the oxide superconductor of its feature, and the quantity of charge carrier is recently determined by the composition of A lattice atoms, as recently being determined by the composition of Sr-La or Ba-Y under the situation of above-mentioned material.Therefore, the state electron density N(O of Fermi surface) also determine by this composition ratio.According to " Bardeen-Cooper-Schrielles theory (being abbreviated as " BCS theory ") ", superconduction critical temperature Tc represents with following formula:
K
BTc＝1.14hw
D×exp（-1/N（O）/V）
Wherein, ω
DBe Debye temperature, V is a parameter of representing electronics-photon interaction size.Thereby, in order to increase superconduction critical temperature Tc, the state electron density N(O of Fermi surface) just must be big.For this reason, must change the method for charge carrier quantity, make the state electron density N(O of Fermi surface by appropriate change A lattice atoms) reach maximum.Yet, in above-mentioned material, the parameter that can change charge carrier quantity has only A lattice atoms composition ratio, promptly the composition of Sr-Lr than or the composition ratio of Ba-Y, make the state electron density N(O of Fermi surface thereby its problem is the number deficiency that causes parameter) reach maximum.
A kind of composite oxides have nickel fluoride potassium (K
2NiF
4) crystal structure, its composition comprises the sesquichloride of the lanthanum of alkaline including earth metal (M) and copper (Cu) ion, this sesquichloride is with formula (La
1-xM
x)
2Cuo
4Expression (wherein M is Sr, Ba or Ca).This is a kind of crystal (space group: D that belongs to tetragonal crystal system
4n-I4/mmm), and have the composite construction of rock salt structure of including and perovskite structure.Rock salt structure and perovskite structure position mutually form sandwich construction thereon.On the other hand, a kind of Y-M-Cu is oxide based, and (wherein M is Sr, Ba and Ca) composite oxides have the crystal structure of similar perovskite, the oxide based sesquichloride that includes the rare earth element of a kind of alkaline including earth metal (M) and copper (Cu) ion of this Y-M-Cu.This rare earth element as the interionic between two kinds of structures every, and copper ion is positioned at oxygen octahedra.So this structure has promptly caused anisotropy having brought different characteristic aspect the interplanar electronics emission of c direction of principal axis and vertical c axle and the conductivity.In recent years, proved with small amount of alkali earth metal (as barium or strontium) replace the part lanthanum and the composite oxides that are prepared into 30 to 40K or higher temperature under show superconductivity, promptly these composite oxides are a kind of superconductors with high-critical temperature.In this superconductor, its c direction of principal axis and and the direction of c axle quadrature between have the superconductivity coherence length that differs ten times.And, this composite oxides can baric and strontium as composition element (M), this just can form by with the compound monoatomic layer that reduces its surface work function of oxidized atom, and this also just makes this composite material be suitable for to make electronic emission material.
But owing to can reduce on the stacked c of the being added in direction of principal axis of single electron of work function, above-mentioned material just shows anisotropy.Therefore, need the monocrystalline of this composite oxides, so that this composite material is in actual applications as electric conducting material.This composite oxide material comprises as La
2O
3, Y
2O
3And CuO, BaO or SrO, they can form the mixing phase in the time of near being heated to fusing point.Therefore, with needing the pulling method of high-temperature digestion can not obtain good monocrystalline.In these cases, up to the present, also do not proposed to drop into the actual method of using for preparing composite single crystal.
The purpose of this invention is to provide a kind of method for preparing the oxide superconductor monocrystalline of high-quality and appropriate size.
The purpose of this invention is to provide a kind of method for preparing the oxide superconductor monocrystalline of high-quality and appropriate size.
Purpose of the present invention can reach with a kind of like this method for preparing oxide superconductor, and this method may further comprise the steps:
Prepare a kind of raw material that is made of at least a composition that is selected from the polycrystalline that La-M-Cu is oxide based or Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca), this composition is K
2NiF
4Crystal structure or be similar to the composite oxides of perovskite crystal structure, described structure has copper ion in the oxygen octahedra center, and this composition can also be the mixture that has with the similar stoichiometry composition ratio of the composition of described composite oxides;
The flux that preparation is made of CuO, this CuO have the fusing point lower than the fusing point of described composite oxides;
Fuse described raw material with described flux.And simultaneously melt temperature is maintained the temperature lower than the fusing point of described composite oxides, and described composite oxides are dissolved in the described flux:
In the saturated flux solution for preparing by the described raw material of fusion, grow the monocrystalline of described composite oxides.
That is to say in the method for the invention, have high-quality and suitably big or small composite oxides M
2CuO
4Monocrystalline can adopt case of flux methods, produce down in the temperature also lower (1026-1300 ℃) than the temperature of the direct fusion method of composite oxides, wherein, the fusing point of component oxide is lower than the fusing point of composite oxides, promptly the CuO(fusing point: about 1026 ℃) or CuO and Cu
2O(fusing point: about 1235 ℃) mixture is as flux.
The basic principle of the inventive method is described now.
According to applicable cases, change size as the monocrystalline of electric conducting material.When monocrystalline is used as superconducting electrode or superconduction electric wire, preferably make several square millimeters thin plate crystal or the film crystal on insulation board.On the other hand, when monocrystalline was used as electronic emission material, although available several square millimeters thin plate crystal, the 1 square millimeter * size of 8 millimeters (length) was enough to as the negative electrode point.
In the present invention, fusing point is lower than the composition oxide of the oxide based or composite oxides fusing point that Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) of La-M-Cu, i.e. CuO(fusing point: about 1026 ℃) or CuO and Cu
2O(fusing point: about 1235 ℃) mixture is as flux (flux), and the monocrystalline of the compound system that La-M-Cu is oxide based or Y-MCu is oxide based crystallizes out from the supersaturated solution of composite oxides.
This cosolvent can be that those satisfy the following flux that requires:
＜1〉it has the lower fusing point of composite oxides fusing point more oxide based than La-M-Cu or that Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca);
＜2〉it is the minimum oxide of fusing point in the component oxide of composite oxides, and can fuse composite oxides fully in molten condition, does not then have solubility or restricted to solubility solid-state.
＜3〉its inexpensive purchasing, and non-environmental-pollution.
＜4〉it can be by acid or the alkali that is dissolved in dilution, or in the hot water, remove at an easy rate, and the composite oxides that will carry out crystallization are to be difficult to dissolving therein.The example of the flux of described requirement comprises the CuO(fusing point above satisfying: about 1026 ℃, it is a kind of component oxide) or CuO and Cu
2About 1235 ℃ of O(fusing point) mixture.
For example, the polycrystalline of the composite oxides that La-M-Cu is oxide based or Y-M-Cu is oxide based that will carry out crystallization (wherein M is Sr, Ba or Ca), perhaps stoichiometric composition than with the composite oxides that comprise component oxide or carbonate (La for example
2O
3, MO and CuO mixture, or Y
2O
8, MO and CuO mixture) stoichiometric composition be dissolved in the above-mentioned flux than the polycrystalline of similar mixed oxide.The flux solution that so obtains is remained under the low-melting temperature of or the composite oxides that Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) more oxide based, to prepare saturated flux solution than La-M-Cu.Crystallization goes out the monocrystalline of the oxide based or composite oxides that Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) of La-M-Cu from this saturated flux solution.Crystallization can be carried out with following two kinds of methods.A kind of method comprises: the generation speed of or Y-M-Cu oxide based (wherein M be Sr, Ba or Ca) composite oxide single crystal oxide based with a little higher than La-M-Cu, and, make the supersaturated solution cooling that remains on said temperature with the basic corresponding cooldown rate of crystal growth rate.In this way can be from above-mentioned saturated flux solution crystallization go out sizable monocrystalline of the oxide based or composite oxides that Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) of La-M-Cu.In addition, control monocrystalline generation speed and crystal growth rate, can be had appropriate size and superior in quality polycrystalline and monocrystalline simultaneously separately by controlling initial chilling temperature and cooldown rate.Another kind method comprises: insert a slice substrate in the supersaturation flux solution under low 10 ℃ the steady temperature approximately remaining in than the maintenance temperature of above-mentioned saturated flux, and make the substrate rotation, thereby on this substrate, form the monocrystal thin films that the quite thick La-M-Cu of one deck is oxide based or Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) by epitaxial growth.
The aforesaid melting method that utilizes flux production to be better than routine based on the method for the electric conducting material of composite oxides.Because crystallization is to carry out under the temperature that is lower than oxide based or Y-M-Cu is oxide based (wherein M is Sr, Ba or the Ca) fusing point (about 1400 ℃) of La-M-Cu, so can obtain monocrystalline and monocrystal thin films that size is suitable for being used as electric conducting material in this way, and can access the high quality single crystal that does not have lattice disorder and internal strain substantially.Therefore, because these advantages also can be carried out retrofit by making wiring pattern at an easy rate.In addition, with basic and the corresponding spacing of eddy current size (about 10nm), at the surface ion implanted dopant (as argon, boron or hydrogen) of high quality crystal, strengthened the blocking effect of magnetic flux, this can make the electric current that can flow through superconductor increase.
Explain the present invention below in conjunction with accompanying drawing.Wherein:
Fig. 1 represents to have ABO
3In the oxide of perovskite crystal structure, the relation between A ionic radius and oxonium ion radius sum and B ionic radius and oxonium ion radius sum;
Fig. 2 represents to have ABO
3In the oxide of perovskite crystal structure, the relation between the ratio of B ionic radius and oxonium ion radius sum and A ionic radius and oxonium ion radius sum and the ionizing energy of B atom;
Fig. 3 is expression (Y
0.3Ba
0.65K
0.05) CuO
3The curve chart of the measurement result that changes with temperature of resistivity;
Fig. 4 is illustrated in the (Y that liquid helium temperature is measured
0.55Ba
0.3K
0.15)
3Cu
2O
7Or Y
0.275Ba
0.15K
0.075CuO
3.5Current-voltage characteristic curve;
Fig. 5 is expression Y(Ba
1-xK
x)
2Cu
3O
7-δThe curve of the measurement result that the resistivity of (wherein x is 0.10 and 0.05) changes with temperature;
Fig. 6 represents YBa
2KCu
3O
7The curve of the measurement result that changes with temperature of resistivity;
Fig. 7 represents YBa
2Cu
3O
7-xF
xThe curve of the measurement result that the resistivity of (wherein x is 0.25) changes with temperature;
Fig. 8 represents YBa
2Cu
3O
7-xF
xThe curve of the measurement result that the resistivity of (wherein x is 1.0) changes with temperature;
Fig. 9 is for representing by chemical structural formula Y
xBa
yB
zCuO
3-yThe schematic diagram of the oxide composition ratio of (wherein x+y+z=1, B is Na, K, Rb or Cs) representative;
Figure 10 for the expression melt temperature to composition of raw material than dependent schematic diagram;
Figure 11 is expression (LaSr)
2CuO
4The curve chart of the measurement result that the resistivity of monocrystalline changes with temperature.
Example 1
Preparation Ba
0.1Sr
0.1La
1.8CuO
4(1-y)The technical process of (wherein y 〉=0):
Is 1.9735 gram purity 99% BaCO
3With 1.4763 gram purity be 99% SrCO
3, 29.3256 gram purity are 99.99% La
3O
3And 24.1600 gram purity be 99.3% Cu(NO
3)
23H
2O is mixed in together.The mixture that obtains is dissolved in the nitric acid, heats this nitric acid simultaneously.An amount of ammonia water is added in the solution that so makes, and adds oxalic acid, adjust the pH value of solution simultaneously, thereby co-precipitation goes out Ba as the precipitation media
2+, Sr
2+, La
3+And Ca
2+Water fully washes sediment, and (clarification) liquid that floats over the upper strata that obtains is discharged.Remaining sediment is dried up, can be made heat treated raw material and use.After the raw material drying, promptly in an atmospheric oxygen atmosphere in 1050 ℃ of following heat treatments 5 hours be the platinum crucible that has in the quartz ampoule of electric furnace, obtain Ba thus
0.1Sr
0.1La
1.8CuO
4(1-y)
With producing the oxide superconductor that except mentioned component, also has following ingredients with above-mentioned same method:
Ba
0.02Sr
0.1La
1.88CuO
4（1-y）
Ba
0.02Sr
0.15La
1.83CuO
4（1-y）
Ba
0.05Sr
0.1La
1.85CuO
4（1-y）
Ba
0.075Sr
0.1La
1.825CuO
4（1-y）
Example 2
Preparation Ba
0.05Sr
0.075La
1.875Cu
0.7Ag
0.3O
4(1-y)The technical process of (wherein y 〉=0):
Is 0.9869 gram purity 99% BaCO
3With 1.1072 gram purity be 99% SrCO
3, 30.5475 gram purity are 99.99% La
2O
3, 16.9120 gram purity are 99.3% Cu(NO
3)
2.3H
2O and 3.4761 gram purity are 99.9% Ag
2O is mixed in together.The mixture that obtains is dissolved in the nitric acid, heats this nitric acid simultaneously.An amount of ammonia water is added in the solution that so makes, and adds oxalic acid, adjust the pH value of solution simultaneously, thereby co-precipitation goes out Ba as the precipitation media
2+, Sr
2+, La
3+, Cu
2+And Ag
+Water fully washes sediment, and (clarification) liquid that floats over the upper strata that obtains is discharged.Remaining sediment is dried up the raw material of handling usefulness as heat supply.After making raw material drying, in an atmospheric oxygen atmosphere in 1050 ℃ of following heat treatments 5 hours, usefulness be the platinum crucible that has in the quartz ampoule of electric furnace, obtain Ba thus
0.05Sr
0.075La
1.875Cu
0.7Ag
0.3O
4(1-y)
Example 3
Preparation (Y will be described in this example
0.3Ba
0.65K
0.05) CuO
3Technical process.
It is 99.99% Y that distilled water is joined 3.3872 gram purity
2O
3, 12.8278 gram purity are 99% BaCO
3, 0.3455 gram purity is 99% K
2CO
3With 7.9545 gram purity be among 99.99% the CuO, then abundant wet lapping 24 hours in ball mill.After the mixture drying that obtains, in an atmospheric oxygen atmosphere,, use the platinum crucible in the electric furnace in 850 ℃ of following heat treatments 10 hours.After this, in the agate alms bowl, fully grind through heat treated mixture.With the powder that obtains again in an atmospheric oxygen atmosphere in 850 ℃ of following heat treatments 10 hours.In the agate alms bowl, fully grind again through heat treated powder.At 5 tons/centimetre
2The following material that obtains of extruding of pressure, it is molded into disk.The heat treatment 10 hours in 1000 ℃, one atmospheric oxygen atmosphere of this disk, thereby obtain (Y
0.3Ba
0.65K
0.05) CuO
3With with above-mentioned same method, just change raw-material amount, can obtain down the oxide superconductor of tabulation shown in 1.
Example 4
This example will be described preparation (Y
0.85Ba
0.1Rb
0.05) CuO
3Technical process.
It is 99.99% Y that distilled water is joined 9.59693 gram purity
2O
3, 1.97339 gram purity are 99% BaCO
3, 0.57736 gram purity is 99% Rb
2CO
3With 7.95454 gram purity be among 99.99% the CuO, then fully wet-milling 24 hours in ball mill.After the mixture drying that obtains, in an atmospheric oxygen atmosphere,, use the platinum crucible in the electric field in 850 ℃ of following heat treatments 10 hours.After this, in agate mortar, fully grind through heat treated mixture.With the powder that obtains again in an atmospheric oxygen atmosphere in 850 ℃ of following heat treatments 10 hours.To in agate mortar, fully grind through heat treated powder again.At 5 tons/centimetre
2The following resulting material of extruding of pressure, it is molded into disk.This disk is carried out hot pressing under following condition: 200 ℃/hour gradient of temperature speed, 1000 ℃ stopping temperature, 10 hours the time of staying and the pressure of 300 crust.So obtained (Y
0.85Ba
0.1Rb
0.05) CuO
3With with above-mentioned same method, just change raw-material amount, can obtain down the oxide superconductor of tabulation shown in 2.
Example 5
This example will be narrated preparation (Y
0.3Ba
0.3K
0.4) CuO
3Technical process.
The target that the discoid polycrystalline that obtains in the example 3 is used as sputter.With sapphire or SrTiO
3Make substrate, substrate temperature is chosen in the temperature range of room temperature to 500 ℃.Carrying out sputter with 1 to 4KV radio-frequency voltage in the mixed-gas atmosphere that comprises argon and oxygen (dividing potential drop of oxygen is 5% or less), is 3000 to 7000 thereby obtain thickness
(Y
0.3Ba
0.3K
0.4) CuO
3Much less, use with above-mentioned same method and can access film as example 3 or example 4 described oxide superconductors.
Narrate the measurement result of the critical temperature Tc of the material that so obtains below.Measure according to generally accepted four-terminal resistance rate method of measurement.Specifically, allow constant current density flow through the sample two ends, then, measure the variation of oxide superconductor its resistivity when superconducting state is transformed into normal conducting state at every square centimeter several amperes electric current.Used Rose-Innes cryostat (its advantage is the cryogenic gas absorption characteristic of activated carbon), rate of rise in temperature has been adjusted to 0.3K/min.Make temperature-sensitive element with golden iron-chromium thermocouple.
Fig. 3 is prepared (Y in the expression example 3
0.3Ba
0.65K
0.05) CuO
3Determination of resistivity result's curve chart.
Fig. 4 is prepared (Y in the expression example 4
0.55Ba
0.3K
0.15)
3Cu
2O
7Or Y
0.275Ba
0.15K
0.075CuO
3.5Under liquid helium temperature, measure I-E characteristic gained result's curve chart.
Also obtained and the identical result of above-mentioned those materials for other material of the present invention.The temperature variant measurement result of the resistivity of relevant these materials is shown in Fig. 5 in Fig. 8.Specifically, Fig. 5 represents Y(Ba
1-xK
x)
2Cu
3O
7-δThe temperature variant measurement result of resistivity of (wherein x=0.10,0.05), Fig. 6 represents YBa
2KCu
3O
7The temperature variant measurement result of resistivity, Fig. 7 represents YBa
2Cu
3O
7-xF
xThe temperature variant measurement result of resistivity of (wherein x=0.25), Fig. 8 represents YBa
2Cu
3O
7-xF
xThe temperature variant measurement result of resistivity of (wherein x=1).
As mentioned above, the present invention can change the quantity of charge carrier, and this not only makes it can allow the state electron density of Fermi surface reach maximum, and helps the stable of structure.This causes the oxide superconductor of having realized easy manufacturing and having had high critical current densities.
Fig. 9 shows by chemical structural formula Y
xBa
yB
zCuO
3-δThe composition of the oxide that (wherein x+y+z=1, B is Na, K, Rb or Cs) is represented is than x: y: z.Point 1,2,3,4 and 5 corresponds respectively to the Y described in the above-mentioned example
0.3Ba
0.65K
0.05CuO
3-δ, Y
0.4Ba
0.55K
0.05CuO
3-δ, Y
0.4Ba
0.3K
0.3CuO
3-δ, Y
0.4Ba
0.5Rb
0.1CuO
3-δAnd Y
0.85Ba
0.1Rb
0.05CuO
3-δAmong Fig. 9, select the summit be in 1,3 and 5 the triangle coordinate values as by the oxide of above-mentioned chemical structural formula representative or proportion by subtraction x: y: z, just can realize the oxide superconductor of production easily.Particularly select summit among Fig. 9 be in 1,3 and 5 the triangle coordinate values as by the composition of the oxide of above-mentioned chemical structural formula representative than x: y: z, the oxide superconductor that can realize improving density and produce easily.
The raising of density helps significantly to improve critical current density.Especially when B is K, the density height of the oxide superconductor that the Y-Ba-K-Cu that makes is oxide based, this will help to realize high Superconducting Current Density.
Example 6
The technology example of oxide superconductor produced according to the present invention is described below.
At first will be to having K
2NiF
4The composite oxides of the La-M-Cu of crystal structure oxide based (wherein M is Sr, Ba or Ca) are done some and are introduced, and in having the oxide of above-mentioned crystal structure, copper ion is included in the center of oxygen octahedra.
This example relates to respectively uses (La
1-xM
x)
2CuO
4Sinter (wherein M is Sr, Ba or Ca) and Cu oxide (Cu
2O.2CuO) prepare the technical process of monocrystalline as raw material and flux.
To describe M in this example is the representational examples of the composite oxides of Sr as this composite oxides.
About 2 grams are comprised (La
0.9Sr
0.1)
2CuO
4The raw material of sinter and the Cu that comprise about 1.47 grams
2The flux of the CuO of O and about 1.63 grams is placed in the platinum crucible, and remains on 1300 ℃ to 1100 ℃ through time enough in air, wherein includes (La thereby form
0.9Sr
0.1)
2CuO
4Saturated cupric oxide flux solution.After this, reduce the temperature of saturated solution with 3 to 70 ℃ cooling rate per hour, with the cupric oxide of preparation solid.
According to (La in the saturated solution of uniform temperature
0.9Sr
0.1)
2CuO
4The quantity of crystal is measured monocrystalline and is produced speed.Then, according to the speed of the magnitude estimation crystal growth of the monocrystalline that forms.
The maximum temperature of used electric furnace is 1500 ℃ in this example.Identify the crystal that so obtains with powder X-ray diffraction or Laue (Laue) diffraction approach.
As raw-material (La
0.9Sr
0.1)
2CuO
4Sinter is by by the prepared in reaction of following reaction equation representative:
Its reaction condition is: in air, calcined 5 hours down at 750 ℃, in air, 1200 ℃ of following roastings 5 hours.
In above-mentioned example, when initial chilling temperature is 1240 ℃, at (La
0.9Sr
0.1)
2CuO
4Sinter can fully be dissolved under the state of the melt oxidation copper in the platinum crucible, and platinum crucible was kept 5 hours, then with 30 ℃/hour cooldown rate with its cool to room temperature.(La
0.9Sr
0.1)
2CuO
4Sinter is still stayed the bottom of platinum crucible, is not dissolved in the cupric oxide of fusion, and but, the centre of observing platinum crucible has some dodging the conduction (La of black light
0.9Sr
0.1)
2CuO
4Monocrystalline.Crystal be shaped as size about 5mm square square.Since 1300 ℃, when cooldown rate is reduced to less than 70 ℃/hr, obtain monocrystalline.When cooldown rate is reduced to less than 30 ℃/hr hour, although the decreased number of monocrystalline can obtain sizable crystal.When cooldown rate is 3 ℃/hr, obtain about 8mm
2Monocrystalline.The cooldown rate that is lower than 3 ℃/hr makes the generation instability of monocrystalline.If the cooling initial temperature is 1300 ℃, although solubility increases, the oxygen in the Cu oxide is tending towards easy decomposition, this makes and is difficult to form high-quality crystal, on the other hand, is 1100 ℃ if cool off initial temperature, because solubility is low, so the crystalline size that generates is very little.Consider the above fact, the cooling initial temperature is preferably 1100-1300 ℃, and cooldown rate is preferably 3-70 ℃/hr.
By replacing Sr above-mentioned, can produce La-M-Cu oxide based (wherein M is Ba or Ca) with Ba or Ca.That is: (La
0.9Ba
0.1)
2CuO
4Or (La
0.9Ca
0.1)
2CuO
4Crystal can by with obtain with the identical step of the situation of Sr, just with about 2 restrain (La, Ba)
2CuO
4Or (La, Ca)
2CuO
4As raw material.
Example 7
This example relates to the technical process for preparing monocrystalline, and wherein, component oxide and the carbonate composition of La-M-Cu oxide based (wherein M is Sr, Ba or Ca) (are SrCO
3, La
2O
3, CuO or Cu
2O) be used as raw material.Weigh up about 0.62 gram SrCO
3, about 6.20 gram La
2O
3, about 4.93 gram CuO and about 4.43 gram Cu
2O is as raw material, and puts into platinum crucible.Because flux is by above-mentioned CuO and Cu
2O forms, so be placed on CuO and Cu in the crucible
2The important stoichiometric composition ratio that surpasses of O.For example, suppose CuO and Cu
2O is the same to the contribution that forms monocrystalline, and the CuO of about 4.09 grams and the Cu of about 3.68 grams then will be arranged
2O is as flux.Raw material kept about 8 hours down at 1300-1100 ℃, so that their abundant fusions in oxygen atmosphere.Relation between melt temperature and proportion of raw material is seen Figure 10.After this, the temperature of flux solution reduces with the specific cooldown rate between 3 ℃/hr to 70 ℃/hr, solution kept several hours being lower than under the about 20 ℃ temperature of raw material solution temperature, found that on the surface of flux solution some are dodging (the La of the conduction of black light
0.9Sr
0.1)
2CuO
4Monocrystalline.These monocrystalline be shaped as size about 5mm square square.Identify the crystal that obtains like this with powder X-ray diffraction or Laue diffraction.
Since 1300 ℃, when cooldown rate reduce 70 ℃/when hr is following, obtain monocrystalline.When cooldown rate be reduced to 30 ℃/when hr is following,, when cooldown rate is 3 ℃/hr, obtain being of a size of about 8mm although the decreased number of monocrystalline can obtain bigger crystal
2Monocrystalline.Make the growth instability of monocrystalline less than the cooldown rate of 3 ℃/hr.If the cooling initial temperature is 1300 ℃, although solubility increases, the copper in the Cu oxide is tending towards easy decomposition, and this makes and is difficult to form high-quality crystal.On the other hand, if the cooling initial temperature is 1100 ℃, because solubility reduces, so the crystal that generates is very little.Consider the above fact, the cooling initial temperature is preferably 1100-1300 ℃, and cooldown rate is preferably 3-70 ℃/hr.
Figure 11 be expression obtain in this example (La, Sr)
2CuO
4The curve of the measurement result that the resistivity of monocrystalline changes with temperature.
In the oxide based situation of La-Ba-Cu, can with about 0.83 the gram BaCO
3Replace SrCO
3, prepare (La
0.9Ba
0.1)
2CuO
3Monocrystalline.Similarly, in the oxide based situation of La-Ca-Cu, can with about 0.42 the gram CaCO
3Prepare (La
0.9Ca
0.1) CuO
4Monocrystalline.
Example 8
This example relates to the technical process for preparing monocrystal thin films, wherein, and (La
0.9Sr
0.1)
2CuO
4Sinter causes the mixed raw material that comprises following composition and makes raw material:
1.475 gram Cu
2O;
1.640 gram CuO;
2.0615 gram La
2O
3;
0.2076 gram SrCO
3
Comprise 2CuOCu
2The Cu oxide of O is as flux.
In platinum crucible, place (the La that comprises of about 10 grams
0.9Sr
0.1)
2CuO
4The raw material of sinter and comprise about 7.35 the gram Cu
2The flux of O and about 8.05 gram CuO.Perhaps, in platinum crucible, place the oxide based component oxide of above-mentioned La-Sr-Cu, i.e. Cu
2O, CuO, La
2O
3And SrCO
3In this case, if make the supposition identical, about 1.081 gram CuO and about 0.972 gram Cu will be arranged then with example 7
2O is as flux.They remain on process time enough under the 1300-1100 ℃ of temperature in air, contain (La with preparation
0.9Sr
0.1)
2CuO
4Cu oxide flux saturated solution.Then, has 5mm comprising
2The SrTiO of the monocrystalline on surface (100)
3Substrate (fusing point: 1900 ℃) is put into supersaturation flux solution, and this solution remains below under the about 10 ℃ temperature of saturated solution temperature.When this substrate of rotation, dodging (the La of the conduction of black light
0.9Sr
0.1)
2CuO
4The monocrystal thin films crystallization is on substrate.Can find from the eroded crater test, use SiTiO
3Substrate can obtain flawless basically high quality crystal film, and this is because SrTiO
3The lattice constant α of substrate
0Be 3.904A, promptly approach (La
0.9Sr
0.1)
2CuO
4Lattice constant.
And then find, inject with the 100Kev ion, in single-crystal surface 0.1 μ m depths, be 10 with peak value
19Ar atom/cm
2Impurity mix, can improve superconduction critical electric current.
When with (La, Ba)
2CuO
4Or (La, Ca
2) CuO
4The sintering powder also can obtain and above-mentioned same result during as raw material basically.
Example 9
The technical process of the composite oxides that prepare the Y-M-Cu oxide based (wherein M is Sr, Ba or Ca) with similar perovskite crystal structure is discussed now, and in above-mentioned crystal structure, copper ion is included in the center of oxygen octahedra.
This example relates to the technical process for preparing monocrystalline, and wherein, the sinter and the Cu oxide (CuO) of the composite oxides of Y-M-Cu oxide based (wherein M is Sr, Ba or Ca) are used separately as raw material and flux.In this example, narration M is the composite oxides of Ba, as the representational example of composite oxides.
In platinum crucible, place the raw material that comprise the oxide based composite oxides sinter of Y-Ba-Cu of about 2 grams, comprise the flux of CuO with about 3.15 grams, in oxygen atmosphere, remain under 1100 ℃-1026 ℃ the temperature through time enough, contain the oxide based saturated Cu oxide flux solution of Y-Ca-Cu to generate in the gram.Then, reduce the temperature of saturated solution with the cooldown rate of 3-70 ℃/hr, with preparation solid copper oxide.
The oxide based monocrystalline of Y-Ba-Cu produces speed and crystal growth rate, is measured by the method identical with the oxide based situation of La-Sr-Cu in the example 8.
The maximum temperature of the electric furnace that uses in this example is 1500 ℃.The crystal of Huo Deing is discerned by powder X ray spread out line or Laue diffraction method like this.
Prepare by the represented reaction of following reaction equation as raw-material sinter:
0.6Y
2O
3+ 1.8BaO+2CuO+0.7O
2Oxide based its reaction condition of=Y-Ba-Cu is:
In air, 750 ℃ of temperature lower calcinations 4 hours, in air, 1000 ℃ of roasting temperatures 5 hours.
In this example, when the cooling initial temperature was 1080 ℃, platinum crucible kept 5 hours under this temperature, made the oxide based sinter of part Y-Ba-Cu can be dissolved in the Cu oxide of fusion in the platinum crucible, then, with the cooldown rate cool to room temperature of 30 ℃/hr.As a result, the oxide based sinter of part Y-Ba-Cu is still stayed the bottom of platinum crucible and is not dissolved in the Cu oxide of fusion.But the oxide based monocrystalline of the Y-Ba-Cu that can observe some conductions of dodging black light is at the core of platinum crucible.
Since 1100 ℃, when cooldown rate is reduced to less than 70 ℃/hr, can obtain monocrystalline, when cooldown rate is reduced to less than 30 ℃/hr, although the decreased number of monocrystalline can obtain bigger crystal.When cooldown rate is 3 ℃/hr, obtain the monocrystalline of large-size.Make the generation instability of monocrystalline less than the cooldown rate of 3 ℃/hr.If the cooling initial temperature is 1100 ℃, although solubility increases, the oxygen in the Cu oxide is tending towards easy decomposition, and this makes and be difficult to generate high-quality crystal that on the other hand, if the cooling initial temperature is 1030 ℃, because solubility reduces, the crystal of generation is very little.From above-mentioned fact-finding, the cooling initial temperature is preferably between 1026-1100 ℃, and cooldown rate is preferably between the 3-70 ℃/hr.
As raw material, also can obtain the result identical basically with the oxide based sinter powder of Y-Sr-Cu or the oxide based sinter powder of Y-Ca-Cu with The above results.
This example is to narrate as a reference as the situation of flux with CuO.With comprising CuO and Cu
2During the flux of O, can repeat the process identical with example 6.
Example 10
This example relates to the technical process for preparing monocrystalline, and wherein, component oxide and carbonate composition that Y-Ba-Cu is oxide based (are BaCO
3, Y
2O
3, CuO) be used as raw material.Weigh up about 39.7772 gram BaCO
3, about 5.645 gram Y
2O
2, about 39.470 gram CuO.They are fully mixed and put into platinum crucible.At this moment, if make with example 7 in identical supposition, then nearly 27.841 gram CuO but in this Y-Ba-Cu is oxide based, need to add the BaCO of half as flux
3As flux as CuO.Mixture remains in oxygen atmosphere in the 1300-1100 ℃ of temperature range, makes the fusion of part raw material, thus the solid mixture of preparation fusion.
Then, saturated solution is cooled to 850 ℃ gradually with the cooldown rate of about 10 ℃/hr.As a result, can in platinum crucible, see the Y-Ba-Cu-O monocrystalline of the conduction that some are dodging black light.Crystal in the form of sheets, size is about 1mm
2, thickness is about 0.1mm.
Example 11
This example relates to the technical process for preparing monocrystal thin films, wherein, and the oxide based sinter of Y-Ca-Cu or comprise Y
2O
3, the mixed raw material of BaO and CuO is as raw material, and the Cu oxide that comprises CuO is as flux.
Weigh up the raw material that comprise the oxide based sinter of Y-Ba-Cu and the 15 gram CuO fluxs of about 10 grams, put into platinum crucible, in air, under 1100-1026 ℃ of temperature, keep time enough, contain the oxide based Cu oxide flux saturated solution of Y-Ba-Cu with preparation.Then, will comprise having 5mm
2The SrTiO of the monocrystalline on surface (100)
3Substrate (fusing point: 1900 ℃) is put into supersaturation flux solution, and this solution remains below under the about 10 ℃ temperature of saturated solution temperature, and during rotary substrate, crystallization goes out dodging the oxide based monocrystal thin films of Y-Ba-Cu of the conduction of black light on substrate.From the eroded crater test, can find, use SrTiO
3Substrate can obtain flawless basically high quality crystal, because SrTiO
3The lattice constant α of substrate
0Be 3.904A, promptly approach (Y
0.4Sr
0.6)
3Cu
2O
7Lattice constant.
And then find that in single-crystal surface 0.1 μ m depths, mix with the injection of 100Kev ion, the peak value of impurity is 10
19Ar atom/cm
2, this helps to improve superconduction critical electric current.
When oxide based the or oxide based sinter powder of Y-Ca-Cu is as raw material with Y-Sr-Cu, also can obtain essentially identical result with the above result.
Claims (9)
1, a kind of method for preparing oxide superconductor is characterized in that comprising:
The preparation raw material, it is grouped into by at least a one-tenth of selecting in or Y-M-Cu is oxide based (wherein M is Sr, Ba or Ca) the polycrystalline oxide based from La-M-Cu, and this composition is K
2NiF
4Crystal structure or be similar to the composite oxides of perovskite crystal structure, in this structure, copper ion is positioned at the center of oxygen octahedra, and this composition can also be the mixture with the stoichiometric composition ratio that is similar to described composite oxides constituent;
The preparation flux, it comprises that fusing point is lower than the CuO of described composite oxides;
Described raw material are dissolved in the above-mentioned flux, keep solution temperature to be lower than the fusing point of described composite oxides simultaneously, and composite oxides are dissolved in the described flux;
Monocrystalline at the described composite oxides of saturated flux growth from solution that make by described raw-material dissolving.
2, method according to claim 1, wherein, the crystal of described composite oxides generates in saturated flux solution by cooling off described saturated flux solution gradually.
3, method according to claim 2, wherein, described saturated flux solution is with the cooldown rate cooling of 3-70 ℃/hr.
4, method according to claim 3, wherein, described saturated flux solution remains below under the about 10 ℃ temperature of described solution temperature, and a substrate is immersed in this saturated flux solution, rotate this substrate then, thereby on this substrate, generate the crystal of described composite oxides.
5, method according to claim 4, wherein, described solution temperature is 1026-1300 ℃.
6, method according to claim 5, wherein, described solution temperature is 1026-1100 ℃.
7, method according to claim 5, wherein, described solution temperature is 1100-1300 ℃.
8, method according to claim 7, wherein, described flux also comprises Cu
2O.
9, method according to claim 7, wherein, the flux that occurs with solid form does not have solubility or restricted to solubility for composite oxides.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18392/87 | 1987-01-30 | ||
| JP62018392A JP2585561B2 (en) | 1987-01-30 | 1987-01-30 | Oxide superconducting material |
| JP42559/87 | 1987-02-27 | ||
| JP63782/87 | 1987-03-20 | ||
| JP8474087 | 1987-04-08 | ||
| JP84740/87 | 1987-04-08 |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN88100501A Division CN1015033B (en) | 1987-01-30 | 1988-01-30 | Oxide superconductor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1038719A true CN1038719A (en) | 1990-01-10 |
| CN1013158B CN1013158B (en) | 1991-07-10 |
Family
ID=26355066
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN89103432A Expired CN1013158B (en) | 1987-01-30 | 1989-05-25 | Process for preparation of superconductors |
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| Country | Link |
|---|---|
| CN (1) | CN1013158B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1312331C (en) * | 2001-06-25 | 2007-04-25 | 独立行政法人产业技术综合研究所 | Method for producing single crystal of composite oxide |
-
1989
- 1989-05-25 CN CN89103432A patent/CN1013158B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1312331C (en) * | 2001-06-25 | 2007-04-25 | 独立行政法人产业技术综合研究所 | Method for producing single crystal of composite oxide |
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| Publication number | Publication date |
|---|---|
| CN1013158B (en) | 1991-07-10 |
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