CN1178563A - Method for obtaining single crystals from peritectic melts - Google Patents

Abstract

A method of preparing single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid.

Description

Obtain the method for monocrystalline from the peritectoid melt

The present invention carries out under the government-funded that Ministry of Energy gives, and contract number is No.W-31-109-ENG-38, and United States Government has some right in this invention.

Generally speaking, the present invention relates to a kind of method of making monocrystalline.More specifically, the present invention relates to that (wick away) or desorb (desorbtion) are gone in a kind of suction by melt and collect the method that the solid monocrystalline obtains from peritectoid stream (flux) melt monocrystalline in the inertia substrate.

Existing have many growing methods, but typically relate at a slow speed, the technology of lower volume.Usually need to produce a large amount of crystal seeds and be used to generate bigger monocrystalline.Have, it will be helpful producing this crystal fast, in large quantities with simple equipment again.

Therefore, an object of the present invention is to provide a kind of improved crystal seed working method.

Another object of the present invention provides a kind of novel method of collecting monocrystalline, and this method is by forming a kind of liquid/solid mixtures and remove liquid, stays at last that the solid crystal seed carries out.

Of the present invention have a purpose to provide a kind of improved method of collecting monocrystalline from liquid again, and this method is by carrying out with an inert, the unwanted liquid of porous substrate desorb.

Of the present invention also have a purpose to provide a kind of new monocrystalline manufacture method, this method be by heat solid group (mass) to being enough to form the temperature that flows melt, this stream melt can remove with desorb.

Of the present invention also have a purpose to provide a kind of improved monocrystalline collection method, and this method is by forming the mixture of monocrystalline and balance liquid phase, this substrate absorption equilibrium liquid phase in inertia, porous substrate.

Of the present invention have a purpose to provide new crystal seed collection method again, and this method is to be undertaken by remove crystal liquid phase on every side with the capillary desorb.

From following detailed and described accompanying drawing, other purposes of the present invention and benefit will become obvious.

The accompanying drawing summary

Fig. 1 has provided the schema that a preferred method of the present invention is described; And

Fig. 2 is expression two Nd that the typical case forms of the present invention ₂O ₃, the pseudo-three-phase of BaO and CuO (pseudoternary phase) figure.

Detailed description of the preferred embodiments

With reference to the flow chart among the figure 1, a kind of method of the present invention is carried out general description. Method of the present invention can Be used for any phase system (phase system) that presents the peritectoid phasor. Using an example of the inventive method is one Plant high-temperature superconductor (HTSC). Suppose so a kind of system, namely one by obtaining initial chemical substance, simple substance (elemental) or chemistry, and weigh up suitable amount to obtain the system of desired composition. In addition, precursor material Material can be a kind of material of chemical combination, and this material is suitable for obtaining desired product when heating, thereby obtains lower The peritectoid equilibrium mixture that face will be described (peritectic equilibrium mixture). Ideally, Precursor material is a kind of material that can reach the required seeded growth condition of the best. In addition, preferably making suspension gives birth to The amount of liquid of long crystal is minimum, but can not be little of crystal is formed together, and this can make independently single monocrystalline of acquisition Target is fallen through. The final form (Morphology) of crystal can also be repaiied in a conventional manner by changing to form Just. As in field of crystal growth known, growth kinetics changes in such peritectoid alpha region; And as To the explanation of example II, people can, such as in a HTSC system, adjust the condition of crystal growth, from And flat crystal is changed over the crystal habit of cubic, this depends primarily on the composition in the peritectoid alpha region Position (compositional location). Like this, as forming temperature and quenching (queching) condition Such parameter can be regulated by the practician in this area easily, thereby obtains required particular crystal form, And number and the size of the crystal seed that obtains.

Referring to Fig. 1, selected precursor material in batches is ground into powder in the preparation of doing for chemical combination again. Typical method With this material of ball mill grinding 4-12 hour in isopropyl alcohol (or other such inert fluids). Generate The grinding pulverulent material is dried, such as stove or the hot plate by a routine; Pulverulent material is pressed into bead then. With these beads that are pressed into of method precalcining of routine, for be heated to peritectoid mutually in required phasor position valid Standby.

Also must prepare substrate and be used for receiving peritectoid liquid and mixed crystal. This substrate has these character, namely to wanting The peritectoid liquid that sucks is inertia, and the tool fusing point is higher than the melting temperature of peritectoid liquid phase. Such substrate is prepared to Can be with this liquid wetting and also present porous, thus can enough this substrates desorb or suction from the mixture that comprises crystal seed Remove peritectoid liquid. For example, substrate can be prepared into a kind of porous small ball, and its fusing point is higher than desired monocrystalline, such as, Resemble Y₂BaCuO _x(211 YBaCu oxide) such solid material can be used for 123 Nd (or Sm) BaCu oxygen The compound system. To Y₂BaCuO _xSystem, these beads are being lower than the about 30% sintering 8-48 of place of fusing point hour.

In next step, the bead of the precursor material after the precalcining is placed in a kind of inertia crucible, such as Al₂O ₃, The material that a kind of noble metal or other do not react with the peritectoid mixture. This crucible and precursor material are heated to one Temperature, and be the equilibrium phase that guarantees basically to be formed in the peritectoid phasor in time. Heat protocol is (with gas gas The atmosphere condition) can follow a variety of conventional thermodynamics routes, but the result should obtain the equilibrium state of required regulation, thereby inhale Remove peritectoid liquid stream, stay crystal seed.

When obtaining desired equilibrium phase mixture, allow seeded growth to obtain specific size and number, this is logical Cross and control in a kind of known, conventional mode that crystal growth condition carries out. Material in the crucible can be with two then Plant a kind of processing the in the optimal way: (1) directly is deposited on above-mentioned perforated substrate with crystal seed/peritectoid liquid mixture On, or (2) quenching peritectoid/crystal seed mixture is deposited on this perforated substrate to form a solid group with this solid group On, should fully heating of group, thus the solid base that initially forms from peritectoid liquid of fusing and suck this liquid only. After removing undesired peritectoid liquid (stream), people's available physical method is taken crystalline substance left on perforated substrate away Kind.

Following indefiniteness embodiment has provided the multiple declaration of method of the present invention.

Example I

A kind of results Nd _1+xBa _2-xCu ₃O _yThe crystalline method may further comprise the steps: the Nd of (1) SILVER REAGENT ₂O ₃, CuO and BaCO ₃With the proportion of composing of 1: 10: 4 (molar percentage) by weighing, (2) these initial precursor materials in a polyethylene bottle with the zirconium oxide abrasive medium in ethanol or Virahol by ball milling 4-12 hour, thereby obtain uniform parent material mixture, (3) powdery parent material is at N ₂Be dried on hot plate under the atmosphere, thereby avoid initial powder and ambient atmosphere to react, (4) dried powder is pressed into bead to reduce contacting of bead and the alumina crucible that is used to melt precursor material; The diameter of typical case's bead is 20mm, quality 20g, and adopt the pressure of 5000-10000pa to be made into bead, (5) bead at 940 ℃ at least by preroasting 24 hours, (6) be heated to about 1050-1100 ℃ and kept about 48 hours then, (7) mixture after the heating by cooling (approximately per hour 1-10 ℃) slowly to about 1000 ℃ to promote the growth of crystal in peritectoid liquid (stream), (8) crucible that includes sample is placed on the copper billet quenching to form solid group, stop the crystalline growth, (9) place a porous Y with the solid group in the crucible ₂BaCuO _xIn the substrate, (10) heat solid is rolled into a ball about 1050 ℃, keeps 2-8 hour, peritectoid liquid (stream) is absorbed or inhales, promptly enter in the vesicular structure by gravity and capillary force, the crystal that (11) stay is cooled to room temperature and (12) are taken crystal seed away from the porous substrate.

Example II

At Nd ₂O ₃(see figure 2) in the/CuO/BaO system is formed by adjusting in the peritectoid region, has made the monocrystalline with different shape. (Nd ₂O ₃), BaO and CuO mix promptly 1: 4: 12.5 and 1: 2: 6.25 with following two ratios.During these are formed each is heated to 950 ℃ and kept 48 hours.When finishing during this period of time, the peritectoid mixture is handled in the mode identical with example I, to collect crystal.Be that crystal has the form of a flat board (flat) under 1: 4: 12.5 the situation at this ratio.At this ratio is 1: 2: 6.25 o'clock, and the crystalline form is a cube shaped.

With reference to the claim that proposes later, further advantage of the present invention and feature can be understood.Though described preferred embodiment,, obviously,, can change and revise not departing under the essence and the situation of scope of the present invention aspect the most complete for the common expert of this area.

Claims (18)

1. A method for preparing a single crystal, comprising the steps of: preparing a precursor material having a composition; heating said precursor material and obtaining a peritectic equilibrium mixture comprising phases of peritectic liquid and crystal; cooling said peritectic equilibrium mixture to form a solid mass; providing a porous substrate inert to said peritectic equilibrium mixture and placing said solid mass on said substrate; absorbing the peritectic liquid with the substrate, leaving a single crystal on the substrate; and The single crystal is removed from the substrate. 2. The method of claim 1, wherein said step of preparing a precursor material comprises preparing a mixture of materials generally relative to said composition. 3. The method of claim 2, wherein said single crystal comprises 123 NdBaCu oxide and said precursor material consists essentially of Nd ₂ O ₃ , CuO and BaCO ₃ in a molar ratio of 1:10:4 percentage composition. 4. The method of claim 1, wherein said single crystal is selected from the group consisting of 123 NdBaCu oxide, 123 smBaCu oxide and 123 YBaCu oxide. 5. The method of claim 1, wherein said step of heating the precursor material comprises heating to the region of the peritectic phase and forming and growing said crystals. 6. The method of claim 5, wherein said step of growing said crystal comprises slowly cooling said mixture of peritectic liquid and crystal through at least said peritectic phase region. 7. The method of claim 1, wherein a crucible is used to contain the precursor material and said crucible consists essentially of a material inert to said peritectic liquid and crystal. 8. The method of claim 1, wherein said substrate comprises a material inert to said peritectic liquid and said crystals. 9. The method of claim 8, wherein said substrate comprises a higher melting point compound consisting essentially of the elemental component present in said single crystal. 10. A method for preparing a single crystal, comprising the steps of: preparing a precursor material having a selected composition; heating said precursor material and obtaining a peritectic mixture comprising phases of peritectic liquid and crystal; providing a substrate that is porous and inert to said peritectic mixture; quenching said peritectic mixture on the substrate; absorbing the peritectic liquid with the substrate, leaving a single crystal on the substrate; and The single crystal is removed from the substrate. 11. The method of claim 10, wherein said precursor material comprises a mixture of compounds. 12. The method of claim 10, wherein said single crystal has a composition selected from the group consisting of123NdBaCu oxide,123SmBaCu oxide and123YBaCu oxide. 13. The method of claim 10, wherein said heating step includes heating to a peritectic phase region to form said single crystal and grow said crystal. 14. The method of claim 13, wherein said step of growing said single crystal comprises slowly cooling said peritectic mixture. 15. The method of claim 10, wherein said heating step includes placing said precursor material in an inert crucible. 16. The method of claim 10, wherein said inert crucible is selected from the group consisting of alumina, noble metal and zirconia. 17. The method of claim 10, further comprising the step of adjusting the composition to cause said precursor material to form different morphologies of said crystals. 18. The method of claim 10, further comprising the step of adjusting crystal growth conditions to form different morphologies of said crystals.