CN1033060C - process for preparing superconductor - Google Patents

Abstract

Bi-Pb-Sr-Ca-Cu-O system and Tl-Pb-Ba-Ca-Cu-O system superconductor having a high Tc phase (about 110 K and about 125 K, respectively, or more) in a high proportion are obtained by adding a calcium compound which forms CaO and a liquid phase at a temperature for firing the superconductors, e.g., Ca2PbOx(x = 3 or 4); or by starting from a composition represented by the formula: Bi2Pb(n-1)/2Sr2CanCun+1Ob min , or T l 2Pb(n-1)/2Ba2CanCun+1Ob where 2 <= n <= 10, 9 <= b <= 40.5, i.e., at a ratio of Ca:Pb = 2:1.

Description

Be used to prepare the technology of superconductor

The present invention relates to be used to prepare the technology of superconductor.More particularly, the present invention relates to be used in short roasting time, prepare the technology of the superconductor of Bi-(Pb)-Sr-Ca-Cu-O system or Tl-Ba-Ca-Cu-O system.

High-temperature superconductor material demonstrates superconductivity and is studied widely and utilize the development progress of these materials rapid under liquid nitrogen temperature.Especially, high-temperature superconductor material is in research and development at the above superconduct of 100k, because they are permitted wide temperature range for filling with liquid nitrogen, high in theory critical current density jc and critical magnetic field hc give material and provide the superconductor with higher Tc, and it can be used as film and lead-in wire.

The Y-Ba-Cu-O series superconducting material has the critical temperature up to about 90K, but chemically unstable, because and H ₂O, CO ₂Cause loss Deng reacting, in being placed on air, can cause the problem in the use superconductivity.

Be higher than the superconductor of 100K as having critical temperature, Bi-Sr-Ca-Cu-O system and Tl-Ba-Ca-Cu-O series superconducting material are known (J.J.A.P.VOl.27.No.2,1988, PP209-210, NIKKEI, ELECTRONICS1988.4.18 (No.55) PP175-177).These Bi systems and Tl series superconducting material are insensitive to water and oxygen, be preparation easily and processing, and there is not the restriction on the source, because they do not comprise rare earth element, and, the Bi series superconducting material have be about 80K low Tc mutually and the high Tc that is about 110K mutually, and the Tl series superconducting material have an appointment 105K low Tc phase and the high Tc that is about 125K mutually; Notice that the high Tc of high these materials of Tc can individually not form mutually.

As you know in prior art Bi-Sr-Ca-(ratio of the high Tc phase of Cu-O series superconducting material can increase (NIKKE SUPERCOND-UCTOR1988.5.16.PP2-3) by adding Pbo.In this technology, the part of Bi is to be substituted by Pb, and oxalates gives fixed ratio (Bi: Pb: Sr: Ca: Cu: O=0.7: 0.3: 1.0: 1.0: 1.8) be used as parent material, 800 ℃ of calcinings 12 hours and 845 ℃ of roastings 240 hours with one.At calcination stage, must avoid the formation and the Ca of low Tc phase ₂PbO _x(x=3 or 4), Ca _xSr _3-xCu ₅O _y, Bi ₂Sr ₂Cu ₁O _xThe generation of intermediate products, and roasting is to carry out under 845 ℃ and temperature maintains and is not higher than 880 ℃.Disclosing out nearly all Pb loses during roasting; When form high Tc mutually and the high Tc phase time Pb of stabilisation formation set up the route of reaction, but the unfavorable place of this technology is the roasting time that requirement reaches 240 hours length.

Reported also that by the researcher of Kyoto university, Mie university and Toda Kogyo having high Tc Bi system mutually holds block and reach by applying Pb, and all be to reach in the Bi system by admixture Pb by the almost single-phase sample of researcher's report of Osaka university and Daikin.By the sample of two kinds of method preparations, the standard synthetic and the solid function of nitrate, the superconductor that their both's generations have the high Tc phase of 107.5K, and the ratio of compound is: Bi: Pb: Sr: Ca: Cu=0.8: 0.2: 0.8: 1.0: 1.4.This technology is the roasting of adopting in Low Pressure Oxygen atmosphere, and the fusing point of this material is lowered and the temperature range that forms high Tc phase is to have widened thus.Roasting to be 842 ℃ be that 80 hours (solid function method) and 828 ℃ are 36 hours.In two kinds of methods, the variation that oxygen is pressed allows roasting at 800-820 ℃, and discloses out, in nitrate n-compound method, 828 ℃ of roastings 36 hours with higher ratio produce high Tc mutually and be a short time roasting example (Trigger88-8, P91-92,1988.7.8).

The Bi-Sr-Cu-O series superconducting material that has Tc and be 70K be by people such as Akimitsu find (Jpm.J.Appl.phys.26,1987.L2080) or people (Z.phys.B68 (1987) 421) such as Michel.

People such as Maeda find the superconductor (Jpn.J.Apple.Plys.27.1988.L209) that high Tc phase Bi-Sr-Ca-Cu-O is, have three superconducting phases, at Bi ₂Sr ₂Ca _N-1Cu _nO _xIn, when Tc is 70K corresponding to n=1, when being 105K corresponding to n=2 and Tc when Tc is 80K corresponding to n=3.Along with n is increased to 3 from 1, the number of the CuO layer in crystal structure is to have increased, and the C axle is to the variation of 437A from 24A to 30A.

Because the single high Tc of above-mentioned superconductor is not artificial mutually, the research of high Tc phase is not also reported out.

People such as Ta Kano have reported that the ratio of the high Tc phase of Bi series superconducting material substitutes Bi by Pb and increases that (Jpn.J.Appl.physics27,1988.L1041), but the effect of Pb is not also clarified.

The purpose of this invention is to provide a kind of technology for preparing superconductor, compare, in shorter roasting time, have the ratio that increases high Tc phase with the prior art of admixture PbO.

Above-mentioned purpose of the present invention is to be reached by the technology for preparing superconductor, and the step that is comprised is: with first kind of material of form preparation of mixture of powders or sintering quality, the component that it had is represented by molecular formula (I):

Bi _{U '}Pb _{V '}Sr _{W '}Ca _{X '}Cu _{Y '}O _z(I) I≤u ＇≤3,0≤v ＇≤1,1≤w '≤3,0≤x ＇≤12,1≤y ＇≤12,3≤z ＇≤39.5 here; First kind of material is added in the calcium compound, this compound forms mixing phase and the liquid phase of CaO, be not higher than under 900 ℃ in temperature, and the mixture of formed first kind of material of roasting and calcium compound, its temperature is not higher than 900 ℃ and is represented by molecular formula (II) to obtain superconductor:

Bi _uPb _vSr _wCa _xCu _yO _z (II)

Here 1≤u≤3,0≤v≤1,1≤w≤2,2≤x≤10,3≤y≤11,6≤z≤35.

Same technology may be used in the Tl series superconducting material, so also can provide the technology of preparation superconductor, and the step that is comprised is: with first kind of material of form preparation of mixture of powders or sintering quality, the composition that is had is by molecular formula (III) representative

Tl _{U '}Pb _{V '}Ba _{W '}Ca _{X '}Cu _{Y '}O _{Z '}(III) 1≤u '≤3,0≤v '≤1,1≤w '≤3,0≤x '≤12,1≤y ＇≤12,3≤z ＇≤39.5 here; First kind of material is spiked in the calcium compound, mixing phase and the liquid phase of this compound form CaO, be not to be higher than under 900 ℃ in temperature, and the mixture that is not higher than 900 ℃ of formed first kind of materials of following roasting and calcium compound in temperature to be to obtain superconductor, and it is to be represented by molecular formula (IV):

Tl _uPb _vBa _wCa _xCu _yO _z(IV) 1≤u≤3,0≤v≤1,1≤w≤2,2≤x≤10,3≤y≤11,6≤z≤35 here.

In best enforcement l example of the present invention, y=x+1; 1.5≤u ＇≤2.5,0≤v '≤1,1.5≤w ＇≤2.5,0≤x '≤4,3≤y ＇≤8,3≤z ＇≤2.5; More in order that 1.5≤u '≤2.5,0≤v '≤0.5,1.5≤w '≤2.5,1.0≤x ＇≤2.0,3.0≤y ＇≤4.0,5.0≤z ＇≤17.0; The compound of calcium is from Ca ₂PbO ₄, Ca ₂PbO ₃, CaCl ₂And Ca ₃OCl (CaO, 2CaCl ₂) group selected; Calcium compound is to add with 10 to 50 percent by weight, is first kind of material of 10 to 20 percent by weight better; Sintering temperature is 750-880 ℃, is more preferably 840-850 ℃ (being higher than this value is the temperature that is used to form liquid phase).Why the reason of 3≤y≤11 is exactly at Bi _2O2Between obtain 3 numbers to the 11CuO layer, and why the reason of 2≤x≤10 is exactly the Ca (Figure 1A is to Fig. 1 C) that is presented at the CuO interlayer.Because superconductor material wherein Bi or Tl to be substituted by Pb be known, so pointed out scope 0≤v≤1, and it is contemplated that component can be from Bi ₂Sr ₂Ca ₂Cu ₃O ₂Or Tl ₂Ba ₂Ca ₂Cu ₃O ₂Detach, so point out scope 1≤w≤2.

According to the present invention, also provided the technology that is used to prepare superconductor, be mixture by the roasting parent material, it is total that this mixture had is to be represented by molecular formula (V) as oxide component

Bi ₂Pb _(n-1)/2Sr ₂Ca _nCu _N+1O _b.... (V) 2≤n≤10,9≤b≤40.5 here are to be under 750～880 ℃ in temperature; And the technology that is used to prepare superconductor is the mixture by the roasting parent material, and it is total that this mixture had is to be represented by molecular formula (VI) as oxide component:

Tl ₂Pb _(n-1)/2Ba ₂Ca _nCu _N+1O _b(VI) 2≤n≤10,9≤b≤40.5 here are to be under 750～900 ℃ in temperature,

By these technology, superconductor is to be represented by following formula (VII)

Bi ₂Pb ₂Sr ₂Ca _aCu _A+1O _{B '}.... (VII) or superconductor be to represent by following formula (VIII):

Tl ₂Pb _vBa ₂Ca _aCu _A+1O _{B '}(VIII) 2≤a≤10,0≤V≤1,8.5≤b ＇≤31.5 here, wherein Pb can contain with part and obtain.The component of parent material is selected as to have than being Ca: Pb=n: (n-1)/2, because the mole (mole) of Ca and Pb is compared to high Tc formation mutually confidential relation is arranged.When PbO is spiked in Bi-Sr-Ca-Cu-O system or the Tl-Ba-Ca-Cu-O series superconducting material, Pb and Ca combine at 750 ℃ or lower formation Ca ₂PbO ₄, it can be broken down into CaO and become liquid phase in the time of 822 ℃.Can think that high Tc is formed by the effect between low Tc phase and the CaO in liquid phase mutually.For forming high Tc phase in short roasting time, low Tc phase and Ca ₂PbO ₄Must be 800 ℃ or above formation.For forming Ca ₂PbO ₄, 2 Mores' calcium requires 1 More's aluminium, so the ratio that PbO should mix is Ca: Pb=n: (n-1)/2.Sintering temperature is chosen as 750～880 ℃ or 750～900 ℃ because when temperature be 750 ℃ or lower, high and low Tc does not form mutually, and superconductor is higher than 880 ℃ (Bi systems) or 900 ℃ (Tl system) in temperature and melts.Why the reason of 2≤z≤10 is at Bi ₂O ₂Obtain the number of 3 to 11 layers CuO layer between the layer as previously mentioned.

The scope of selected sintering temperature is 750 to 900 ℃ under the superconductor situation of Tl system, and its reason is similar to top given.

Figure 1A is the superconductor crystal configuration diagram to 1C.

Fig. 2 is the phasor of CaO-PbO system,

Fig. 3 is CaCl ₂The phasor of-CaO system,

Fig. 4 A shows the resistance that depends on sample temperature to 4D, admixture the PbO of prior art,

The x ray that Fig. 5 A shows sample to 5D is recommended and is penetrated figure, is the PbO of prior art,

Fig. 6 shows the no accrete sample x ray diffraction pattern of example as a comparison,

Fig. 7 shows 17 hours prepared Ca of 817 ℃ of following roastings in air ₂PbO _xThe x x ray diffration pattern x,

Fig. 8 shows the Ca according to the present invention ₂PbO _xBe spiked into the x x ray diffration pattern x in the sample.

Fig. 9 shows the resistance of the sample temperature dependent among Fig. 8,

Figure 10 shows Ca ₂PbO is spiked into the x x ray diffration pattern x of the sample in the Bi-Sr-Cu-O system,

Figure 11 shows the resistance that depends on temperature among Figure 10,

Figure 12 shows Ca2PbO _xBe spiked into the x diffraction pattern of the sample in the Bi-Sr-Ca-Cu-Q system,

Figure 13 shows the resistance that sample among Figure 12 depends on temperature,

Figure 14 A and 14B show the SEM image on the break cross section and the surface of sample in the example 4,

The magnetization curve of measured sample when Figure 15 shows 77.3K in the example 4,

Figure 16 shows the Jc that estimated in the example 4 curve to applying magnetic field,

Figure 17 shows the Jc of another sample in the example 4;

Figure 18 shows the SEM in the cross section of breaking of another sample in the example 4.

Figure 19 shows by roasting under 841 ℃ of situations 10 hours, and 50 hours, 200 hours ratio of components was Bi: Pb: Sr: Ca: Cu=0.7: 0.3: 1: 1: 1.8 prepared samples depend on the resistance of temperature;

Figure 20 shows the x x ray diffration pattern x of the sample among Figure 14,

Figure 21 shows the Ca of roasting ₁PbO _xRaman (Raman) spectrum with the pill of Bi-Sr-Ca-Cu-O system.

It is Bi: Pb: Sr: Ca: Cu=2: x that Figure 22 shows in 15 hours components of 841 ℃ of roastings: the x x ray diffration pattern x of the sample that 2: 2: 3 (x=0,0.5 and 1.0) are prepared.

Figure 23 shows 750 ℃ of roastings and was quenched into room temperature in 9 hours then, and component is Bi: Pb: Sr: Ca: Cu=2: 0.5: 2: 2: the x x ray diffration pattern x of 3 prepared samples.

Figure 24 shows that to have component be Bi: Pb: Sr: Ca: Cu=0.7: 0.3: 1: 1: 1.8 sample 1C and Ca ₂PbO _x30% weight ratio be spiked into the x x ray diffration pattern x of the sample in the Bi-Sr-Cu-O system.

Figure 25 shows that to have component be Bi ₂Pb ₂Sr ₂Ca ₂Cu ₄O _yThe diffraction pattern of x ray of sample.

Figure 26 shows the resistance of sample temperature dependent among Figure 20;

Figure 27 shows has B component i ₂Pb ₁₅Sr ₂Ca ₄Cu ₅O _yThe diffraction pattern of x ray of sample; And

Figure 28 shows the resistance of the sample temperature dependent among Figure 22.

The critical temperature of well-known Bi series superconducting material is with Bi in crystal lattices ₂O ₂The increase of the CuO number of plies of interlayer increases.Work as Bi ₂O ₂Between the number of CuO layer be 1 o'clock, critical temperature Tc is 7 to 22K; When it was 2, Tc was about 80K, and Tc is 110K when it is 3.The crystal structure of superconductor is shown among Fig. 1 like this.Ca is that interlayer is at Bi ₂O ₂Between the CuO layer of interlayer, the crystal structure that therefore has many CuO layers requires corresponding high Cu and the content of Ca.When additional Ca was in crystal, liquid state was favourable, and this is because Ca spreads easily.For finishing this point, the present invention utilizes calcium compound formation CaO and its temperature near liquid phase, but preferably is lower than the fusing point of superconductor, can carry out roasting at this melting temperature.Best sintering temperature is to be about 750～880 ℃ and calcium compound to be preferably in 900 ℃ or lower formation liquid phase.Such calcium compound comprises Ca ₂PbO ₄(Ca ₂PbO ₃), CaCl ₂, Ca ₃OCl ₄, or the like.

For the Tl series superconducting material also is available equally, though best sintering temperature is to be about 750～900 ℃ and calcium compound preferably 900 ℃ or lower formation liquid phase.

Fig. 2 and 3 shows the phasor of the calcium compound with the best temperature range that so is used to form CaO and liquid phase.Fig. 2 shows the phasor of CaO-PbO system: work as CaO here greater than 13.5 Ying Er percentages (eutectic point), CaO+Liq (liquid) is 822 ℃ or the formation of higher point mutually; Here be meant greater than 13.5 More's percentages and arrive less than 66.7 molar percentages, PC ₂(CaPbO ₃)+Liq (liquid) is lower than 822 ℃ and be higher than 815 ℃ of formation in temperature, and eutectic crystal P+PC ₂(Ca ₂PbO ₃) mixed crystal is to be lower than 815 ℃ of formation in temperature; And it is greater than 66.7 molar percentages here, and CaO+Liq (liquid) is 882 ℃ or the formation of higher point mutually, and Ca ₂PbO ₃The mixed crystal of+CaO is to form when temperature is lower than 822 ℃.

Fig. 3 shows CaO-CaCl ₂The phasor of system: work as CaO here greater than 18.5 molar percentages, and CaO+Liq (liquid) is 835 ℃ or the formation of higher point mutually.(subsidiary says here when CaO be greater than 18.5 More's percentages to less than 33.3 More's percentages and temperature be higher than 750 ℃ be lower than 835 ℃, formation Ca ₃OCl ₄+ Liq (liquid) phase).So utilization has the CaO-CaCl of the CaO of 18.5 More's percentages or bigger percentage ₂Component, CaO+Liq (liquid) is on good terms 835 ℃ or higher formation.

Example 1 (comparison)

Parent material is Bi ₂O ₃, SrCO ₃, CaO, CuO and PbO, on purity be have greater than 99.9% and granular size be 2 to 3 μ m.The weight ratio of these materials is Bi: Sr: Ca: Pb: Cu=0.7: 1: 1: 0.3: 1.8, and to mix and grind and be shaped under the pressure of 200MPa and roasting 841 ℃ time the in air, roasting time is to change to 10,50,99 and 200 hours.

The electrology characteristic of formed Bi series superconducting material is measured and its x x ray diffraction is also detected.Fig. 4 A shows electrology characteristic and Fig. 5 A to 4D and shows the x x ray diffraction situation of 10,50,99 and 200 hours sample of roasting respectively to 5D.The Tc as can be seen from Fig. 4 A to 4D _EndBe to rise along with the increase of roasting time.To 5D, the peak value of (C axle: 30A °) is corresponding to (002) face of low Tc phase and 2 θ=4.8 (.37A ° on C axle) (002) face corresponding to high Tc phase in 2 θ=5.7 from Fig. 5 A.The peak value of (200) face of high as can be seen Tc phase is to strengthen along with the increase of roasting time from 5A to 5D.This is corresponding to Fig. 4 A Tc in the 4D _EndAbove-mentioned increase place.

From x x ray diffraction pattern as can be seen, even roasting 200 hours, the ratio of high Tc phase is lower than the Tc phase ratio.

Example 2 is (Ca ₂PbO ₄Be spiked in the Bi-Sr-Ca-Cu-O system)

For comparison purpose, be similar to those parent materials in the example 1 by weight for Bi: Sr: Ca: Cu=2: 2: 2: 3, mix, grind also and under the pressure of 200MPa, be shaped, then 841 ℃ of roastings 9 hours in air.The powder x x ray diffraction of formed sample is shown among Fig. 6, and wherein the peak value in 2 θ=5.751 ° is corresponding to Bi ₂Sr ₂CaCu ₂(002) face of Oz and the high Tc phase that does not have to form peak with 2 θ=4.8 °.

Then, above-mentioned sample (roasting) is ground the Ca of the percentage by weight of adding ₂PbO ₄, mix, grind and under the pressure of 200MPa, be shaped.Along with 841 ℃ of following roastings in air 30 hours.Ca ₂PbO ₄Preparation 817 ℃ of following roastings in air formed in 17 hours.Ca ₂PbO ₄The diffraction pattern of powder x ray be shown in Fig. 7.Though CaO-PbO system is illustrated in Fig. 2, PC mutually ₂=PbO2CaO, that is the material C a of top institute admixture ₂PbO ₃By the mixture of CaO and PbO Ca: Pb=2 in proportion: 1 in air 817 ℃ of following roastings be prepared in 17 hours, cross with ASTM table cartoon the x x ray diffraction of institute's roasting material thought Ca ₂PbO ₄.Ca in the present invention ₂PbO ₄And Ca ₂PbO ₃The both may be utilized, because the valence electron of Pb is permitted.

Formed sample is to be detected and be the results are shown among Fig. 8 by powder x x ray diffraction.Shown in Figure 8.Corresponding to the peak value of (002) face of high Tc phase (2 θ=4.8 °) is to be better than peak corresponding to (002) face of low Tc phase (2 θ=5.8 °).

Fig. 9 show the sample that forms with respect to the resistance of temperature.Tc _EndBe 103K.

According to prior art admixture PbO and according to the present invention admixture Ca ₂PbO ₄The result comparison under tabulate in 1.

The high Tc phase of table 1 additives roasting time/low 200 hours 0.7Ca of Tc phase PbO ₂PbO ₃30 hours 1.5

As can be seen from Table 1, valency be the additives ratio that is used to increase high Tc phase at the Bi-Sr-Ca-Cu-O series superconducting material, use Ca ₂PbO ₄Be better than PbO.

Example 3 (admixture Ca ₂PbO ₄To Bi-Sr-Cu-O system (no calcium))

Bi ₂O ₃, SrCO and CuO are by Bi: Sr: Cu=2: 2: 3 weight rate, mix, and grind and under 200MPa pressure, be shaped then, then 840 ℃ of following roastings 10 hours in air.The x x ray diffration pattern x is demonstrated out corresponding to 2 θ=4.8 of (002) face of high Tc phase ° does not have peak value, as shown in Figure 6.

To this example, add above-mentioned Ca ₂PbO ₄To provide ratio in Bi-Sr-Ca-Cu-O system is Bi: Sr: Ca: Cu=2: 2: 2: 3.Then with the 840 ℃ of following roastings 40 hours in air of this material.Formed sample x x ray diffraction and detect resistance depend on variation of temperature and be shown in Figure 10 and 11 in.

From Figure 10 and 11 very clearly point out high Tc appearance mutually be since admixture Ca ₂PbO ₄In the x of Figure 10 x ray diffraction pattern, can be observed peak corresponding to high Tc phase (2 θ=4.8 °), and in Figure 11 in the resistance of temperature dependent, Tc _EndBe about 110K.

Example 4

Parent material is Bi ₂O ₃, PbO, SrCO ₃, CaO and CuO powder are to be Bi-Sr-Ca-Cu-O=2 with the nominal composition: the preparation of 2: 1.5: 3.5 solid function, mix, grind then and under pressure, be shaped, 820 ℃ of following roastings 6 hours in air then, and with 14.5% Ca ₂The PbO powder is spiked in the powder of these roastings and removes Ca ₂PbO _xPowder is that 817 ℃ of following roastings formed in 17 hours in air: formed mixture is mixed, grinds 845 ℃ of roastings 23 hours in air then.This material is mixed, grinds, and is that being shaped to form radius under the pressure of 200MPa is that 15mm and thickness are the disk of 2mm at pressure, 845 ℃ of following roastings 80 hours in air then.

Figure 12 shows the diffraction pattern of the powder x ray that forms sample.Peak value in 2 θ=4.8 ° is corresponding to (002) face of high Tc phase.Though corresponding to Bi-Sr-Cu-O system and Ca ₂PbO _x2 θ=7.2 ° and the little value at 11.7 ° peak exist, do not see the peak value in 2 θ=5.7 ° corresponding to (002) face of low Tc phase.It is that the unit born of the same parents are foursquare that the sign of all peak values is based on hypothesis.The a axle is 0.54mm (5.4A °) and the c axle is 3.7nm (37A a °).Figure 13 shows the relation of the resistance temperature dependent of sample.The landing of resistivity can find out it is at 110K, and Tc _EndBe 100K.

The SEM image in the surface and the cross section of breaking is shown in Figure 14 A and 14B.The observation in cross section can be imagined high Tc and be made up of constructional surface mutually.From the x ray diffraction pattern on surface, viewed c axle orientation is to be better than dust figure, and clearly looks more hurry up and the orientation of c axialite body is formed by synthesis technique along the high Tc interpromoting relation in five elements of a-b face, and this technology compresses the powder that high Tc is contained in mutually.The surface of sample can be observed by electro-probe micro analyzer (EPMA), and the cation ratio is to be about Bi: Pb: Sr: Ca: Cu=1.9: 0.3: 1.6: 1.9: 3.4.This this value is almost equal result in the inductively coupled plasma icp analysis.

Figure 15 shows the measured magnetization curve of 77.3K.Be proportional to magnetic field in the following magnetization of 10 oersteds, this magnetic field is subcritical field Hc ₁Corresponding to the Hc below 6.5 oersteds ₁Magnetization value be-0.129emu/g.The density of sintered body is 3.8g/cm ³The degaussing factor of n is 0.54, and it almost is onesize ellipse that imagination disc sample can approach.The percentage by volume of the superconducting phase more than 77.3K is 74%.This is to be worth coming by-4 π M/H.See from the powder diffraction pattern and not have low Tc phase.This percentage by volume that can be envisioned for high Tc phase is 74%.

Critical current density jc can estimate from the magnetic hysteresis of magnetic susceptibility of hypothesis critical state model.-individual simple equation is as follows: (Dhys.Rev.Lett.8 (1962) 250)

Jc (A/cm ²)=30 Δ M/d (1) are M (emu/cm here ³) be the magnetic hysteresis of the magnetization and the thickness that d is sample strip.The Jc that utilizes equation (1) to be estimated is to be shown in Figure 16 for the magnetic field that is applied.Adding magnetic field be 1.25 * 10 ²The Jc estimation is 2.3 * 10 during oersted ³A/cm ²The ratio that Jc reduces in magnetic field is the corresponding ratio greater than Y-Ba-Cu-O system.

The Jc that is recorded by electric-resistivity method at 77.3K is 47A/cm ², be to utilize 10 μ v/cm standards resulting from the V-I characteristic curve.Clearly: the difference at Jc between electric-resistivity method and magnetization method is to be caused by the low-density in grain boundary and the sintered body.

Another sample carries out manufacturing in 50 hours under 845 ℃ with roasting method after sample is contracted by weight.The density of this sample is to be increased to 4.5g/cm from 3.8 ³Go out Jc and be increased to 3.0 * 10 by resistance measurement ²A/cm ², as shown in figure 17.Figure 18 shows the fine structure in sample burst cross section, and can observe the orientation of high c axle.The Tce of this sample is 100K, this be with sample by weight contract before Tce identical.The Tce that people such as Endo (Jpn.J.Appl.phys.27 (1988) L1476) have reported Bi-Pb-Sr-Ca-Cu-O system is 107.5K, and obviously, the impurity that exists in the grain boundary is influence Tce, although because Jc is increase and Tce is constant.

Example 5 (admixture Ca ₂PbO _xInfluence to Bi-Pb-Sr-Ca-Cu-O system)

The preparation of sample is to be Bi: Pb: Sr: Ca: Cu=0.7 by solid function with cationic composition ratio: 0.3: 1: 1: 1.8 and 2: x: 2: 2: 3 (x=0,0.5 and 1.0), parent material was Bi ₂O ₃, PbOSrCO ₃, CaO and CuO, they are mixed and grinding in ball grinder 24 hours, and being shaped to form diameter under 200MPa pressure then is that 15mm and thickness are the pill of 3mm.Preparation condition is as shown in table 2.

Table 2 sample

(℃) No Bi Pb Sr Ca Cu temperature hour atmosphere 1A ^*0.7 0.3 1.0 1.0 1.8 841 10 air 1B ^*0.7 0.3 1.0 1.0 1.8 841 50 air 1C ^*0.7 0.3 1.0 1.0 1.8 841 200 air 2A, 2.0 0.0 2.0 2.0 3.0 841 15 air 2B, 2.0 0.5 2.0 2.0 3.0 841 15 air 2C, 2.0 1.0 2.0 2.0 3.0 841 15 air 2D, 2.0 0.5 2.0 2.0 3.0 750 9 air

(being quenched into room temperature) 3A 2.0 0.0 2.0 0.0 3.0 841 24 air 3B 0.0 1.0 0.0 2.0 0.0 817 17 air 3C sample 3At sample 3B (30 weight %) 848 74 air

(30wt%) note: ^*Be meant prior art.

Sample 3C uses Bi: Sr: Cu=2: 2: 3, obtain in 840 ℃ of following roastings preparation in 6 hours Bi-Sr-Cu-O system; The Ca of admixture and mixing 30 weight % ₂Pbo _x848 ℃ of following roastings 24 hours; Under 200MPa pressure, be shaped; And 848 ℃ of following roastings 50 hours.

Carried out the measurement of resistance, X-ray diffraction; And the Raman of sample (Ramer) spectrum.

Figure 19 shows the relation of sample 1A to the resistance temperature dependent of 1C.For sample 1A, can be observed the decline of resistivity at 110K, but TC end is 74K.Though the beginning temperature of sample 1B is identical with sample 1A, TC end is increased to 85K from 74K.And then when roasting time is when being longer than sample 1A and 1B, resistance drops to when 170K approximately

, and TC end is increased to 103K.

Figure 20 shows the X-ray diffraction pattern of sample 1A, 1B, 1C.Along with the increase of roasting time, the peak in 2 θ=4.8 ° is to have strengthened.This peak value is corresponding to high TC phase (002) face and the C axle is 37A °.The X-ray diffraction figure illustrates that the increase of high TC phase increases along with roasting time.

In sample 1A, to observe and have the not specified material that diameter is 10 μ m, it is differentiated out by fine Raman scattering.It the results are shown among Figure 21, is that the Raman spectrum with sample 3B compares.The X-ray diffraction interpret sample 3B of sample 3B is Ca ₁Pbo _xSingle-phase, (Z.anorg.allgem.Chem.371,1969.237) as shown in Figure 7.In the not specified material of sample 1A and sample 1B, observe 200 and 1000Cm ^-1Between 6 Raman spectrums (255,340,354,422,540,562Cm ^-1).Thus, very clearly Pbo is spiked into to go among the Bi-Sr-Ca-Cu-O be to form Ca ₂Pbo _xReason.

Ca ₂Pbo _xThe main peak of x ray diffraction pattern be 17.70 as shown in Figure 7, and in the x ray diffraction pattern of Bi-Pb-Sr-Ca-Cu-O system, can observe (Figure 15).Along with this peak value of increase of roasting time is to have weakened, to the surface of Bi-Pb-Sr-Ca-Cu-O system Ca is described also by microscopic examination ₂Pbo _xBe that increase or minimizing along with roasting time is line style.

Figure 22 shows the X-ray diffraction figure of sample 2A, 2B and 2C.Work as X=0, promptly sample 2A observe weak peak in 2 θ=5.7 ° and the peak of 2 θ=7.3 ° and 2 θ=4.8 ° be not observed.In other words, high TC is not to be Bi: Sr: Ca: Cu=2 by stoicheiometry (Stoichiometric) component mutually: 2: 2: 3 synthetic under the situation of condition (sample 2A) as shown in table 2.Notice that the peak in 2 θ=7.3 ° is corresponding to (002) face of the Bi-Sr-Cu-O system with 24A ° on C axle.When X is 0.5 (sample 2B), the peak of observing in 2 θ=4.8 °, it is corresponding to high TC phase (002) face.When X is 1.0 (sample 2C), and do not observe high TC and observe low TC mutually and Bi-Sr-Cu-O be.Ca ₂Pbo _xThe peak strengthen along with the increase of Pbo.High TC is Bi: Pb: Sr: Ca: Cu=2: x in component: synthetic and appropriate addition content Pbo was X=0.5 in 2: 2: 3.

Figure 23 shows the X-ray diffraction that was quenched into the sample 2D of room temperature 750 ℃ of roastings in 9 hours then, only observes peak 2 θ corresponding to (002) face of Bi-Sr-Cu-O system=7.3 °, at 750 ℃, and Ca ₂Pbo _xSynthetic with Bi-Sr-Cu-O system and find Fails To Respond CuO another mutually.

The principal phase of sample 3A is a Bi-Sr-Cu-O system.Figure 24 shows the X-ray diffraction figure of sample 3C, Ca in 3C ₂Pbo _xBe spiked among the sample 3A.Can see that having formed high TC phase (100K level) and high TC is 10 times of sample 1C in prior art with respect to the ratio of low TC phase (80K level).The X-ray diffraction explanation of sample 2D, at 750 ℃, high TC phase (100K level) and low TC (80K level) not formation mutually, but formed Ca ₂PbO _xWith Bi-Sr-Cu-O based compound (10K level).After 15 hours, the Bi-Sr-Cu-O based compound disappears and forms high with mutually low 841 ℃ of roastings.Illustrate at Ca more than 822 ℃ at the phasor shown in Fig. 2 (people Erzmetall such as U.Kuxmann, 27,1974,533) ₂PbO _xBe broken down into a CaO and a liquid phase.Can think that when forming high this two-phase of TC phase time be to work as ccelerant.The existence of imagination CaO and liquid phase quickened two CuO layers of Bi-Sr-Ca-Cu-O based compound and the CaO of the decomposition of in liquid phase, moving between reaction.

Ca and Pb are combined into Ca ₂PbO _xCa: Pb=2 in proportion: 1.Why sample 2B (X=0.5) form high TC mutually and sample 2C (X=1.0) can not to form the reason of high TC phase be that reaction between CaO and PbO occurs in Ca: the ratio of Pb is 2: 1.Bi-Sr-Cu-O based compound and Ca ₂PbO _xBe 750 ℃ or lower formation.Low TC phase (80K level) with two CuO layers can be 800 ℃ or higher formation.In sample 2B, Ca ₂PbO _x(0.5 mole) is to form in the time of 750 ℃ and low TC utilizes left Ca ion at 822 ℃ or lowlyer form down.In the time of 822 ℃, Ca ₂PbO _xBe broken down into CaO and liquid phase.High TC can think to be formed by the reaction between low TC phase and CaO mutually.When x is 1.0 (sample 2C), hang down TC and can in the time of 800 ℃, not form because the Ca ion is inadequate (Ca mutually ₂PbO _xAt first in the time of 822 ℃, CaO is added in the Bi-Sr-Cu-O system).

Effect in Bi-Pb-Sr-Ca-Cu-O system is checked to Pb.Ca ₂PbO _xBe 750 ℃ or lower formation and high TC is by Ca mutually ₂PbO _xBe added in the Bi-Sr-Cu-O based compound and form, this compound has single CuO layer.High TC can think by in 822 ℃ of formed liquid phases that mutually the reaction between low TC phase and Ca ion forms.

As other additives, CaAl ₂O ₄, CaSiO ₄, CaSO ₄Deng being considered to form high TC phase, because during roasting Bi-series superconducting material, can not form liquid phase owing to its high-melting-point.

Example 6 (Bi ₂Pb ₁Sr ₂Ca ₃Cu ₄O _b)

Carry out the similar technology done as in above-mentioned the exemplifying, except parent material is weighed to form Bi ₂Pb ₁Sr ₂Ca ₃Cu ₄O _bMix, grind, Cheng Xing And 840 ℃ of following roastings 72 hours in air under 200MPa pressure then.

The x x ray diffration pattern x of formed sample is as shown in figure 25.The peak of high as can be seen TC phase is the Yi that is better than low TC phase.

Figure 26 shows the relation that sample resistance depends on temperature.TC end is 103K.

Example 7 (Bi ₂Pb _1.5Sr ₂Ca ₄Cu ₅O _b)

Carry out the similar technology done as in above-mentioned exemplifying, except parent material is weighed to form Bi ₂Pb _1.5Sr ₂Ca ₄Cu ₅O _bMix the Mo Sui And 840 ℃ of following roastings 72 hours that under 200MPa pressure, are shaped then in air.

The x x ray diffraction pattern of formed sample as shown in figure 27.The Yi of high as can be seen TC phase is the peak that is better than low TC phase.

Figure 23 shows the relation of the resistance temperature dependent of sample.TC end is 103K.

In example 5 to 7, the component that forms high TC phase can be represented by the following formula molecular formula:

Bi ₂Pb _(n-1)/2Sr ₂Ca _nCu _(n+1)Ob is n=2 (example 5) here, n=3 (example 6) and n=4 (example 7)

Can be considered to Bi (Pb)-Sr-Ca-Cu-O system and Tl (Pb)-Ba-Ca-Cu-O series superconducting material and handling in the same manner, therefore, for people skilled on present technique, clearly, for Bi (Pb)-the same consideration of Sr-Ca-Cu-O system may be used on Tl (Pb)-Ba-Ca-Cu-O system.

Claims (14)

1. be used to prepare the technology of superconductor, the step that comprises is:

Preparing first kind of material, is to form with mixture of powders or sinter, and the component that it had is represented by molecular formula (I):

Bi _{U '}Pb _{V '}Sr _w' Ca _x' Cu _{Y '}O _{Z '}I here 1≤u '≤3,0≤v '≤1,1≤w '≤, 0≤x '≤12,1≤y '≤12,3≤z '≤39.5;

Calcium compound is added in first kind of material with formation comprises that CaO mixes mutually and 900 ℃ of temperature or lower liquid phase; And

Formed first kind of mixtures of material of roasting and calcium compound, 900 ℃ of temperature or a lower superconductor to obtain to represent by molecular formula II:

Bi _uPb _uSr _wCa _xCu _xO _z(II) 1≤u≤3,0≤v≤1,1≤w≤2,2≤x≤10,3≤y≤11,6≤z≤35 here.

2. according to the technology of claim 1, wherein in molecular formula (II), y=x+1.

3. according to the technology of claim 1, wherein above-mentioned calcium compound is Ca ₂PbO ₄, Ca ₂PbO ₃, CaCl ₂And Ca ₃OCl ₄Group family in one of.

4. according to the technology of claim 1, wherein above-mentioned calcium compound is Ca ₂PbO ₄Or Ca ₂PbO ₃

5. according to the technology of claim 1, wherein in molecular formula (I), 1.5≤u '≤2.5,0≤v '≤1,1.5≤w '≤2.5,0≤x '≤4,3≤y '≤8,3≤z≤25.

6. according to the technology of claim 5, molecular formula (I) wherein, 1.5≤u '≤2.5,0≤v '≤0.5,1.5≤w '≤2.5,1.0≤x '≤2.0,3.0≤y '≤4.0,5.0≤z '≤17.0.

7. according to the technology of claim 1, the amount that wherein above-mentioned calcium compound is added into is 10% to 50% by weight.

8. according to the technology of claim 7, the amount that wherein above-mentioned calcium compound is gone into by admixture is 10% to 20% by weight.

9. according to the technology of claim 1, wherein above-mentioned roasting is to carry out under 750 ℃ to 880 ℃ of temperature.

10. according to the technology of claim 9, wherein above-mentioned roasting is to carry out under 840 ℃ to 850 ℃ of temperature.

11. be used to prepare the technology of superconductor, be mixture by the roasting parent material, total component that it has as oxide is to be represented by molecular formula (V):

Bi ₂Pb _(n-1)/2Sr ₂Ca _nCu _N+1O _b(V) 2≤n≤10,5≤b≤40.5 here, temperature is at 750 ℃ to 900 ℃.

12. according to the technology of claim 11, wherein in molecular formula (V), 2≤n≤6,9≤b≤28.

13, according to the technology of claim 22, wherein in the molecular formula (V), 2≤n≤4,5≤b≤21.

14. according to the technology of claim 11, wherein formed above-mentioned superconductor is by molecular formula (VI) expression down:

Bi ₂Pb _vSr ₂Ca _aCu _A+1O _{B '}(VI) 2≤a≤10,0≤v≤1,8.5≤b '≤31.5 here.