CN100419346C - Ferroelectric ceramic micro refrigerator and producing method thereof - Google Patents
Ferroelectric ceramic micro refrigerator and producing method thereof Download PDFInfo
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- CN100419346C CN100419346C CNB2004100092103A CN200410009210A CN100419346C CN 100419346 C CN100419346 C CN 100419346C CN B2004100092103 A CNB2004100092103 A CN B2004100092103A CN 200410009210 A CN200410009210 A CN 200410009210A CN 100419346 C CN100419346 C CN 100419346C
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B21/00—Machines, plants or systems, using electric or magnetic effects
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2321/00—Details of machines, plants or systems, using electric or magnetic effects
- F25B2321/001—Details of machines, plants or systems, using electric or magnetic effects by using electro-caloric effects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
Abstract
The present invention relates to a ferroelectric ceramic micro refrigerator and a producing method thereof. The present invention is characterized in that the micro refrigerator adopts a double stage overlapping refrigeration structure. The micro refrigerator of the present invention is prepared by adopting a Sol-Gel wet preparation method of the sosoloid of Pb (Mg<1/3>Nb<2/3>) O<3> in a relaxation property with a high electricity produced heat effect and PbTiO3 (PT) (PMNT for short). Moreover, a novel reification thinning method and an electricity production heat property testing means are adopted. The wet Sol-Gel preparation method of the present invention can effectively suppress the formation of pyrochlore phases during a following sintering process. The present invention solves problems of component segregation, introduced metal ion impurities, etc., which are caused by uneven mix during a dry ceramic mixing process of the prior art. The ceramic forming condition of the present invention is lower than that of the normal PMNT ceramic preparation process. The ferroelectric ceramic micro refrigerator of the present invention has advantages of light weight, small size, no noise, no pollution and simple structure. Refrigeration can be directly started by applying an electric field, and refrigerant is not needed. In addition, the present invention also has advantages of fast refrigeration start and high refrigeration efficiency and is particularly applicable for the low power refrigeration of micro scale devices.
Description
Technical field
The present invention relates to a kind of little refrigerator and preparation method thereof, particularly little refrigerator of ferroelectric ceramics and preparation method thereof.
Background technology
Be widely used at present little refrigerator various refrigeration modes, as working material being carried out mechanical compress and applies electric field and magnetic field, mainly based on following three kinds of principles:
1) semiconductor bismuth telluride-base pn knot refrigeration comes from amber ear card (Peltier) effect, but the barrier height that comes from after all in the carrier transition process changes;
2) freezing by change of state, come from material latent heat of phase change variation under the inductive condition, as cryosel phase transformation cooling, dry ice phase transformation cooling, liquid evaporative cooling and other solids distillation cooling etc., fluorine Lyons (CFC) refrigeration and the present lithium bromide refrigerating that generally adopts that is eliminated the nineties in last century has been exactly typical solution-air freezing by change of state;
3) Entropy Changes refrigeration comes from the adiabatic Entropy Changes effect of material under the inductive condition, is exactly typical Entropy Changes refrigeration as the magnetic refrigeration.Say on the stricti jurise that freezing by change of state also should belong to the Entropy Changes refrigeration in fact, is the Entropy Changes form that a kind of physical form changes.
Some other refrigeration modes such as throttling refrigeration, pulse tube refrigeration, radiation refrigeration and thermoacoustic refrigeration etc. all fail to promote the use of than extreme condition in response to being used for some.
For seeking the new refrigeration approach that is applied to room temperature range, the adiabatic demagnetization refrigeration has appearred in the eighties in last century, and is once becoming hot topic.The U.S., France and Japan etc. have grasped than mature technique in low temperature (mK to 20K scope) magnetic refrigeration research field, have made refrigeration device, are just seeking suitable magnetic refrigerating working material to improve its refrigerating capacity and efficient in room temperature range at present.But the expensive development and the application that has also limited room temperature magnetic refrigerating of obtaining difficulty and rare-earth magnetic working material of high-intensity magnetic field in the magnetic Refrigeration Technique.Because high electric field is than the easy acquisition in highfield, and equipment is simple, adds the low cost of ferroelectric material, ferroelectric depolarising refrigeration effect more is applicable to the room temperature refrigeration than the magnetic refrigeration.The nineties in last century, the researcher considered to adopt the Entropy Changes refrigeration of Relaxation Ferroelectrics, and when promptly under adiabatic condition ferroelectric material being applied external electric field, the effect that its temperature changes, this effect are called again that backheating is released electrical effect or electricity is given birth to heat (EC) effect.As document 1.Shebanov L A, Bornman K J.The application of Ferroelectric and PiezoelectricMaterials.Ferroelectrics, Vol.127,1992:143; 2.Xiao D Q, Zhu J G, Yang B, et al.Ferroelectric refrigeratory materials and their application.Piezoelectric andAcoustooptics, Vol.16 (8), 1994:31～35 etc. are described, and states such as Russia have reported employing relaxation property Pb (Sc
1/2Nb
1/2) O
3, Pb (Mg
1/3Nb
2/3) O
3(being called for short PST, PMN respectively) ferroelectric sosoloid is realized adiabatic depolarising refrigeration near room temperature, this research has been established technical foundation for worldwide ferroelectric refrigeration research.
But there are some technical problems in ferroelectric refrigerator by the principle blank in the evolution of practicality device, and especially for adapting to modern high integration and the miniature heater members of high-energy-density and the needs of system day by day, refrigerator itself also must be microminiaturized.Ferroelectric working material and heater members are adopted the integrated and compatible microfabrication of MEMS (MEMS) technology one chip on the Si substrate, optimal selection beyond doubt, but this requires high-quality ferroelectric thick film material more than deposition 10 μ m on the Si substrate, and this technology still is in the exploratory stage at present.
For reaching microminiaturized requirement, as the ferroelectric ceramics working medium thin slice of ferroelectric refrigeration device, its thickness range is 50 μ m～700 μ m, and must be evenly.Prior art employing mixing paster mode is with ferroelectric refrigeration device and treat that refrigerator is assembled together, but there is following defective in its assembly structure and committed steps such as ferroelectric ceramics and its working medium preparation of sections at refrigerator:
1) the refrigeration assembly structure of individual layer, this structure needs the high driving voltage about 1500V, and can't regulate refrigeration capacity.Therefore refrigerator that must the design sandwich construction, reducing the driving voltage under the same thickness, and the alternative work when strengthening kind of refrigeration cycle.
2) there is the batch mixing inequality in the conventional dry pottery preparation process and causes problems such as composition segregation and introducing impurity metal ion.
3) adopt wafer lapping machine to be difficult to obtain thickness below 200 μ m, the uniformity reaches the ferroelectric ceramics thin slice more than 90%, can't prepare large-area thin slice and adopt high-precision crystal cut machine because equipment price is expensive, be unfavorable for applying of ferroelectric refrigerator.
4) employing thermocouple contact test block ceramic EC effect is relatively sensitiveer down for traditional silicon oil immersion bubble, and ferroelectric refrigeration capacity reduces after the working material microminiaturization, sensitivity is that the thermocouple about 0.1 ℃ is difficult to survey the small EC effect of working medium thin slice, therefore must adopt to have more highly sensitive temperature detection means.
Summary of the invention
For overcoming the shortcoming of prior art, the present invention proposes a kind of new little refrigerator of ferroelectric ceramics and preparation method thereof.The little refrigerator of ferroelectric ceramics of the present invention adopts the refrigeration structure mode of twin-stage overlapping, adopts the relaxation property Pb (Mg with high EC effect
1/3Nb
2/3) O
3With PbTiO
3(PT) sol-gel (Sol-Gel) wet preparation method of (abbreviation PMNT) solid solution, and adopt new materialization attenuate mode and electricity to give birth to heat (EC) Performance Detection means.
The little refrigerator of ferroelectric ceramics of the present invention is in light weight, volume is little, noiseless, pollution-free, and is simple in structure, can directly freeze by applying electric field, do not need to use cold-producing medium; Cooling activation is fast, freezes easily/thermal conversion; Refrigerating efficiency height, cost are low, are particularly useful for the small-power refrigeration of minute yardstick device.
The technical solution used in the present invention:
The little refrigerator of ferroelectric ceramics of the present invention adopts the refrigeration structure of " twin-stage overlapping ".Being characterized as of this structure: will be coupled by the low-temperature eutectic ceramic process by the double-layer ferro-electricity potsherd that two individual layer ferroelectric ceramics sheets are formed, so-called " twin-stage " structure when forming duty, again that two " twin-stage " structures are superimposed at thermal-arrest mica sheet tow sides and mica sheet, form so-called " overlapping " structure.In the refrigeration structure of this " twin-stage overlapping ", each layer ferroelectric ceramics sheet upper and lower surface is all draped over one's shoulders the Sn/Ag electrode, the shared one deck Sn/Ag of " twin-stage " structure electrode, heat-conducting silicone grease rise and quicken conduction of heat between ferroelectric ceramics sheet coated bottom Sn/Ag electrode and mica sheet; Two " twin-stage " structures are corresponding in mica sheet positive and negative position.
The little refrigerator of ferroelectric ceramics of twin-stage overlapping structure of the present invention is the operation principle of freezing when adopting the ferroelectric depolarising, so its duty must comprise and adds the positive field polarization and add two processes of reversed electric field depolarising.The concrete course of work is:, begin to increase progressively field intensity with 4kV/ (cm.min) speed by force by null field and end to 16kV/cm as positive field with (0～16) kV/cm, finish polarization process; Switch input electrode polarity then, equally with (0～16) kV/cm as reversed electric field, begin to end by force by the 16kV/cm field intensity with 8kV/ (cm.min) speed field intensity to the null field that successively decreases, finish process of depolarization.Adopt this polarization at a slow speed and the working method of rapid depolarization, can effectively increase the clean refrigerating capacity of one-cycle process; Twin-stage overlapping structure can reduce the driving voltage under the same overall thickness at double, and by the electric field break-make control to a certain cooling piece, the alternative work when strengthening kind of refrigeration cycle obtains refrigeration capacities at different levels.As to gross thickness being the twin-stage overlapping structure of 1mm, containing 4 thickness respectively is 200 μ m cooling pieces, need only apply 320V voltage can make and apply field intensity and reach 16kV/cm, and if to take thickness be the individual layer cooling piece of 800 μ m, then must apply 1280V voltage just can make and apply field intensity and reach 16kV/cm, and this individual layer cooling piece has only 1 group of electric field break-make to select, and obtains a kind only and causes refrigeration capacity.
The method and the processing step that prepare the little refrigerator of ferroelectric ceramics of the present invention are as follows:
1. preparation abbreviates the relaxation property Pb (Mg of PMNT as
1/3Nb
2/3) O
3With PbTiO
3Solid solution
With the pure Pb (C of homemade analysis
2H
3O
2)
2Powder, chemical pure Ti (OC
4H
9)
4Solvent and Mg (C
2H
3O
2)
2And the pure Nb of electronics
2O
5Powders etc. are raw material, press Pb (Mg
1/3Nb
2/3) O
3(being called for short PMN) and PbTiO
3(being called for short PT) mol ratio is 85/15 prescription, and makes the excessive 4～6mol% of Mg composition, the excessive 5～8mol% of Pb composition in sample.
1) it is miscible in the ethylene glycol ethyl ether organic solvent at first will to meet the above-mentioned raw materials of stoichiometric proportion, obtains leucosol (Sol).
2) colloidal sol (Sol) is inserted in the ball grinder, the abundant ball milling through 8～10 hours, each material component obtains the PMNT presoma with the molecular level immixture at this moment.
3) the PMNT presoma is inserted in the IR bake at 120～180 ℃ down after the abundant dry gelling, put into resistance furnace and distinguish pre-burning 2 hours down, obtain the pre-crystallization powder of PMNT at 450～490 ℃ and 750～800 ℃.
4) the pre-crystallization powder of PMNT is adopted mould compacting green compact, mold pressing 120～180Mpa; Prepare the thick PMNT pottery of 1～3mm solid solution according to conventional ceramic sintering process at last, the sample sintering temperature is 1180～1250 ℃, is incubated 1～2 hour.
Wet method process for preparing sol-gel of the present invention, its technical characterictic is that raw material is mixed with molecular level under the solid-liquid admixture, be that intermolecular interaction has taken place before sintering raw material, branched structure in the colloidal sol interpenetrates, twine, assemble or reset and form highly cross-linked polymerized unit, this polymerization process can effectively suppress the formation of burnt green stone phase in the follow-up sintering process, and the batch mixing inequality causes problems such as composition segregation and introducing impurity metal ion in the ceramic batch mixing process of the dry method that has solved prior art, and because raw material fully mixes, free energy of activation required in the sintering process reduces, and this just causes the one-tenth porcelain condition of this technology of preparing to be lower than conventional PMNT pottery preparation technology.
2. attenuate PMNT potter material and detection electricity are given birth to heat (EC) effect
(1) after relaxation property PMNT pottery is made, adopts wafer lapping machine coupled ion grinding process attenuate
1) elder generation with the thick PMNT ceramics sample of 1～3mm attenuate, reserved the thick surplus of 50 μ m with wafer lapping machine before reaching desired thickness.
2) adopt the ion mill to be etched to desired thickness (thickness is decided because of need for refrigeration capacity) then.Ion mill etching technics parameter is: polar plate spacing 20mm, high frequency power 500W under the 10MHz, vacuum 0.13Pa, etching gas SF6, gas flow 30～40mL/min, etch period 20～25min.
3) adopt aqueous medium ultrasonic cleaning mode to remove sheet surface etching residue, can obtain even bright and clean PMNT ceramic sheet.
The ion grinding process is finished rear section etching residue will stick to sheet surface, thereby the fineness that influences thin slice influences the stability of follow-up plated electrode technology.And adopt mechanical polishing process to be easy to damage the following thin slice of 100 μ m, so the present invention adopts aqueous medium ultrasonic cleaning mode to remove the etching residue, obtains even bright and clean PMNT ceramic sheet.The present invention adopts the ion grinding process, can guarantee the thickness evenness of ceramic sheet and the uniformity and the stability of the electric-field intensity that applies.
(2) chemical etching technology attenuate
1) will go up the PMNT ceramic sheet polishing that a processing step makes, coat polymethyl methacrylate (PMMA) photoresist with the dip-coating mode at the ceramic sheet edge.
2) before 3 160～190 ℃/30min hot plates after baking technology and the photographic fixing of 1 isopropyl alcohol (IPA) fixing solution, it is thick that the PMMA photoresist reaches 100～150nm approximately.
3) adopting best mol proportioning is HCl/HF/NH
4F=1: 3: 15～20 mixed liquor obtains the ceramic sheet of the no undercutting phenomenon in surface as etching liquid, adopts the acetone rinsing at last, obtains bright and clean ceramic sheet.
Experiment shows: above-mentioned processing range can guarantee the compactness that photoresist is good, and the principal element that influences the attenuate effect under this prerequisite is an etching liquid.It is HCl/HF/NH that the present invention obtains best etching liquid mol proportioning through experiment
4F=1: 3: 15～20, there is not the undercutting phenomenon with this ceramic sheet any surface finish that obtains, etch rate 3～5 μ m/min adopt the acetone rinsing at last, obtain bright and clean ceramic sheet.Ceramic sheet grind with etching process in, adopt screw-thread micrometer directly to measure to the thickness more than about 100 μ m, adopt the accurate burnt method of light microscope to draw etching depth and thickness to the thin slice below about 100 μ m.
The reduction process of aforesaid PMNT potter material, all take the on-mechanical polishing, preparation thickness is 50 μ m～700 mu m ranges, any surface finish, the uniform ferroelectric ceramics working medium of thickness thin slice, and smoothness and thickness evenness can guarantee the uniformity of the electrode stability and the electric-field intensity that applies.
(3) detect electricity and give birth to heat (EC) effect
The present invention adopts the contactless real-time testing ferroelectric ceramics thin slice EC of coming of infrared temperature detector (or infrared video camera) effect.Its basic step is: earlier the ferroelectric ceramics sheet is inserted in the plexiglass tent, again lead-in wire is drawn, connect DZ2670A Hi-pot Tester binding post, by this Hi-pot Tester it is applied field intensity at last, by the variations in temperature of infrared probe detection ferroelectric ceramics sheet, and by infrared temperature detector displays temperature value (or infrared video camera displays temperature distribution map).In this test structure, take following measure to improve measuring accuracy:
1) adopts plexiglass tent to make atmosphere draught-free in the test environment, thereby reduce the convection heat losses;
2) adopt 1/2 spatial resolution infrared probe, temperature measurement accuracy is 0.02 ℃, much smaller than 0.1 ℃ of resolution ratio of thermocouple;
3) heat insulation support of employing and mat insulation reduce the energy exchange between sample and base;
4) adopt high accuracy DZ2670A Hi-pot Tester, the high direct voltage that puts on the sample is provided;
5) adopt φ 200 μ m Al/Cu alloy silks to make lead-in wire to reduce the loss of heat conduction loss and Joule heat.
Because no semiconducting doped chemical, ceramics sample resistivity is because of in T Ω rank, and leakage current intensity is in the nA rank, and the Joule heat of sample itself should be less than 0.001 ℃, below the temperature detection sensitivity of this experiment.So under environment temperature kept preferably situation, institute's probe temperature changes should come from the EC effect.Should reduce by the ferroelectric refrigeration capacity in microminiaturized back, the present invention adopts high accuracy infrared temperature detector to come real-time non-contact testing working medium EC effect, and more traditional adopts thermocouple contact method of testing convenient under silicone oil soaks.
3. adopt the low-temperature eutectic ceramic process to make the refrigeration structure of twin-stage overlapping
1) elder generation divides the PMNT ceramic sheet into the square sheet of homalographic; Evenly apply low-melting Sn silver slurry, the coating scope side of being slightly smaller than sheet area of containing again on square sheet two sides;
2) folded to be incorporated in upper and lower surface and to fold up diameter between the two be that the Al/Cu alloy silk of 150～200 μ m goes between with square sheet;
3) lamination layer that will be in then under the clamp position is inserted 300～400 ℃ of following pre-burning 10～15min in the resistance furnace; Insert 750～800 ℃ of following sintering 25～30min again, make to contain the abundant wetting coating of Sn silver slurry, and infiltrate ceramic interfacial layers.
4) polishing is by 3) the multilayer refrigeration structure edge that makes to be to prevent short circuit; The oxide layer of polishing electrode outlet line reaches prefluxing thereon;
5) containing the thick PMMA photoresist of the about 100nm of Sn silver electrode surface employing spin coating proceeding coating up and down to eliminate electric spark.
6) on the dual-in-line base, weld prepared this refrigeration structure at last, form the little refrigerator of ferroelectric ceramics.
So far, the little refrigerator preparation of ferroelectric ceramics of the present invention is finished.
Description of drawings
Fig. 1. the structural representation of the concrete embodiment of the little refrigerator of ferroelectric ceramics of the present invention, among the figure: 1Sn/Ag electrode, 2 PMNT ferroelectric ceramics thin slices, 3 heat-conducting silicone greases, 4 thermal-arrest mica sheets.
X-ray diffraction analysis (XRD) collection of illustrative plates of Fig. 2 .PMNT pottery.
Fig. 3 .PMNT ferroelectric ceramics EC effect detection device schematic diagram is among the figure: 11 plexiglass tents; 12 infrared temperatures probe; 13 ceramics samples, 14 heat insulation supports, 15 electrodes, 16 insulation and thermal insulation pads, 17 separate infrared temperature measurers, 18 Hi-pot Testers.
The refrigeration situation of the thick PMNT ceramic sheet of Fig. 4 .100 μ m under different condition.
The specific embodiment
The little refrigerator of ferroelectric ceramics of the present invention adopts the refrigeration structure of " twin-stage overlapping ".As shown in Figure 1, in the refrigeration structure of this " twin-stage overlapping ", each layer ferroelectric ceramics sheet 2 upper and lower surfaces are all draped over one's shoulders Sn/Ag electrode 1 (the shared one deck Sn/Ag of " twin-stage " structure electrode), heat-conducting silicone grease 3 is between ferroelectric ceramics sheet coated bottom Sn/Ag electrode and thermal-arrest mica sheet 4, rise and quicken conduction of heat, two " twin-stage " structures are corresponding in mica sheet positive and negative position.
Embodiment 1: to analyze pure Pb (C
2H
3O
2)
2Powder, chemical pure Ti (OC
4H
9)
4Solvent and Mg (C
2H
3O
2)
2And the pure Nb of electronics
2O
5Powders etc. are raw material, press Pb (Mg
1/3Nb
2/3) O
3With PbTiO
3Mol ratio is 85/15 prescription, and makes the excessive 4mol% of Mg composition, the excessive 5mol% of Pb composition.The above-mentioned PMNT raw material that at first will meet stoichiometric proportion are miscible in the ethylene glycol ethyl ether organic solvent, obtain leucosol.Colloidal sol is inserted in the ball grinder, the abundant ball milling through 8 hours, each material component obtains the PMNT presoma with the molecular level immixture at this moment.The PMNT presoma is inserted in the IR bake at 120 ℃ down after the abundant dry gelling, put into resistance furnace and distinguish pre-burning 2 hours down, obtain the pre-crystallization powder of PMNT at 450 ℃ and 750 ℃.The pre-crystallization powder of PMNT is adopted mould compacting green compact, mold pressing 120Mpa; Prepare the thick PMNT pottery of 1～3mm solid solution according to conventional ceramic sintering process at last, the sample sintering temperature is 1180 ℃, is incubated 1 hour.
Embodiment 2: to analyze pure Pb (C
2H
3O
2)
2Powder, chemical pure Ti (OC
4H
9)
4Solvent and Mg (C
2H
3O
2)
2And the pure Nb of electronics
2O
5Powders etc. are raw material, press Pb (Mg
1/3Nb
2/3) O
3With PbTiO
3Mol ratio is 85/15 prescription, and makes the excessive 6mol% of Mg composition, the excessive 8mol% of Pb composition.The above-mentioned PMNT raw material that at first will meet stoichiometric proportion are miscible in the ethylene glycol ethyl ether organic solvent, obtain leucosol.Colloidal sol is inserted in the ball grinder, the abundant ball milling through 10 hours, each material component obtains the PMNT presoma with the molecular level immixture at this moment.The PMNT presoma is inserted in the IR bake at 180 ℃ down after the abundant dry gelling, put into resistance furnace and distinguish pre-burning 2 hours down, obtain the pre-crystallization powder of PMNT at 490 ℃ and 800 ℃.The pre-crystallization powder of PMNT is adopted mould compacting green compact, mold pressing 160Mpa; Prepare the thick PMNT pottery of 1～3mm solid solution according to conventional ceramic sintering process at last, the sample sintering temperature is 1250 ℃, is incubated 2 hours.
Embodiment 3: to analyze pure Pb (C
2H
3O
2)
2Powder, chemical pure Ti (OC
4H
9)
4Solvent and Mg (C
2H
3O
2)
2And the pure Nb of electronics
2O
5Powders etc. are raw material, press Pb (Mg
1/3Nb
2/3) O
3With PbTiO
3Mol ratio is 85/15 prescription, and makes the excessive 5mol% of Mg composition, the excessive 7mol% of Pb composition.The above-mentioned PMNT raw material that at first will meet stoichiometric proportion are miscible in the ethylene glycol ethyl ether organic solvent, obtain leucosol.Colloidal sol is inserted in the ball grinder, the abundant ball milling through 9 hours, each material component obtains the PMNT presoma with the molecular level immixture at this moment.The PMNT presoma is inserted in the IR bake at 160 ℃ down after the abundant dry gelling, put into resistance furnace and distinguish pre-burning 2 hours down, obtain the pre-crystallization powder of PMNT at 470 ℃ and 800 ℃.The pre-crystallization powder of PMNT is adopted mould compacting green compact, mold pressing 140Mpa; Prepare the thick PMNT pottery of 1～3mm solid solution according to conventional ceramic sintering process at last, the sample sintering temperature is 1200 ℃, is incubated 1.5 hours.
The PMNT solid solution that adopts Auger electron spectroscopy and X-ray diffraction analysis (XRD) to judge to obtain by embodiment 3 become the porcelain situation.The result shows: the PMNT pottery that obtains is pure perovskite phase structure diffraction maximum, do not have assorted peak and exist, and ceramic constituents meets predetermined chemical metering ratio.Fig. 2 is the XRD figure spectrum of the PMNT pottery that obtained by embodiment 3.The Sol-Gel technology of preparing has effectively suppressed the formation of Jiao Lvshi phase as can be seen from Figure, and the one-tenth porcelain condition of this technology of preparing is lower than conventional PMNT pottery preparation technology.
Adopt the chemical etching technology attenuate of ceramic edge photoresist protection.Earlier that PMNT is ceramic polished, the edge takes the dip-coating mode to coat polymethyl methacrylate (PMMA) photoresist, after baking technology and the photographic fixing of 1 isopropyl alcohol (IPA) fixing solution, it is thick that the PMMA photoresist reaches 100～150nm approximately before 3 160～190 ℃/30min hot plates.Experiment shows: above-mentioned processing range can guarantee the compactness that the PMMA photoresist is good, and the principal element that influences the attenuate effect under this prerequisite is an etching liquid.It is HCl/HF/NH that the present invention adopts best etching liquid mol proportioning
4F=1: 3: 15～20, there is not the undercutting phenomenon with this ceramic sheet any surface finish that obtains, etch rate 3～5 μ m/min adopt the acetone rinsing at last, obtain bright and clean ceramic sheet.Ceramic sheet grind with etching process in, adopt screw-thread micrometer directly to measure to the thickness more than about 100 μ m, adopt the accurate burnt method of light microscope to draw etching depth and thickness to the thin slice below about 100 μ m.
To the bright and clean even ceramic sheet that obtains through above-mentioned ceramic preparation technology and reduction process, adopt the infrared temperature detector to come its EC effect of real-time testing.As shown in Figure 3, ceramics sample 13 is inserted in the plexiglass tent 11, adopt heat insulation support 14 and insulation and thermal insulation pad 16 as with the thermal insulation structure of base, by electrode 15 lead-in wire is drawn again, connect DZ2670A Hi-pot Tester 18 binding posts, apply field intensity by the DZ2670A Hi-pot Tester, by the variations in temperature of infrared temperature probe 12 detection ferroelectric ceramics sheets, and by SCIT separate infrared hygrosensor 17 displays temperature values.
Through experiment, major parameter and performance indications that the little refrigerator of ferroelectric ceramics of the present invention reaches are as follows:
Heat absorption efficiency: 109mJcm
-3
The thick 5cm of 430 μ m
2PMNT ceramic sheet single-stage refrigeration capacity: θ
0=4.7mW;
(the These parameters prior art is respectively μ Jcm
-3, μ W level);
Refrigeration work consumption: 2 * 10
-5Wmm
-3
Operation temperature area: 260-320K;
Energy conversion efficiency:＞85%.
Fig. 4 is the refrigeration situation of the thick PMNT ceramic sheet of 100 μ m under different condition.The maximum linear electricity is given birth to heat (EC) effect E C as shown in Figure 4
Maxδ T is 1.71 ℃ (the single-stage single cycle is at 18 ℃ and the reverse process of depolarization of 16kV/cm).
Adopt the low-temperature eutectic ceramic process to make the refrigeration structure of twin-stage overlapping.
1) elder generation divides the PMNT ceramic sheet into the square sheet of homalographic; Evenly apply low-melting Sn silver slurry, the coating scope side of being slightly smaller than sheet area of containing again on square sheet two sides;
2) folded to be incorporated in upper and lower surface and to fold up diameter between the two be that the Al/Cu alloy silk of 150～200 μ m goes between with square sheet;
3) lamination layer that will be in then under the clamp position is inserted in the resistance furnace, at 300～400 ℃ of following pre-burning 10～15min; Insert 750～800 ℃ of following sintering 25～30min again, make to contain the abundant wetting coating of Sn silver slurry, and infiltrate ceramic interfacial layers;
4) polishing 3) the multilayer refrigeration structure edge that makes is to prevent short circuit; The oxide layer of polishing electrode outlet line reaches prefluxing thereon;
5) containing thick polymethyl methacrylate (PMMA) photoresist of the about 100nm of Sn silver electrode surface employing spin coating proceeding coating up and down to eliminate electric spark;
6) on the dual-in-line base, weld prepared refrigeration structure at last and form the little refrigerator of ferroelectric ceramics.
So far, the little refrigerator preparation of embodiment of the invention ferroelectric ceramics is finished.
The little refrigerator of ferroelectric ceramics of the present invention can be widely used in small size and have the device of general heat dissipation power and the refrigeration of system, as using in microminiature low temperature in microelectronic component, instrument and meter, the medicine equipment or the thermostat, especially in the cooling of large scale integrated circuit (ULSI), light-sensitive device, power device, high frequency transistor, MEMS and MOEMS elements such as (MOEMS) and equipment.
Claims (2)
1. little refrigerator of ferroelectric ceramics, the double-layer ferro-electricity potsherd (2) that it is characterized in that being made up of two individual layer ferroelectric ceramics sheets is by the coupling of low-temperature eutectic ceramic process, form " twin-stage " structure, the ferroelectric ceramics sheet (2) of two " twin-stage " structures is superimposed at thermal-arrest mica sheet (4) tow sides and mica sheet, each layer ferroelectric ceramics sheet (2) upper and lower surface is all draped over one's shoulders Sn/Ag (1) electrode, the shared one deck Sn/Ag of " twin-stage " structure electrode; Heat-conducting silicone grease is positioned between the coated bottom Sn/Ag of ferroelectric ceramics sheet electrode (1) and the mica sheet (4); Two " twin-stage " structures are corresponding in mica sheet (4) positive and negative position.
2. method for preparing the little refrigerator of ferroelectric ceramics is characterized in that its processing step is as follows:
1) preparation abbreviates the relaxation property Pb (Mg of PMNT as
1/3Nb
2/3) O
3With PbTiO
3Solid solution;
To analyze pure Pb (C
2H
3O
2)
2Powder, chemical pure Ti (OC
4H
9)
4Solvent and Mg (C
2H
3O
2)
2And the pure Nb of electronics
2O
5Powders etc. are raw material, press Pb (Mg
1/3Nb
2/3) O
3With PbTiO
3Mol ratio is 85/15 prescription, and makes the excessive 4～6mol% of Mg composition, Pb composition excessive (5～8) mol% in sample;
(1) it is miscible in the ethylene glycol ethyl ether organic solvent to meet the above-mentioned raw materials of stoichiometric proportion earlier, obtains leucosol;
(2) colloidal sol is inserted in the ball grinder, the abundant ball milling through 8～10 hours, and each material component obtains the PMNT presoma with the molecular level immixture at this moment;
(3) the PMNT presoma is inserted in the IR bake at 120～180 ℃ down after the abundant dry gelling, put into resistance furnace and distinguish pre-burning 2 hours down, obtain the pre-crystallization powder of PMNT at 450～490 ℃ and 750～800 ℃;
(4) the pre-crystallization powder of PMNT is adopted mould compacting green compact, mold pressing 120～180Mpa; Prepare the thick PMNT pottery of 1～3mm solid solution according to conventional ceramic sintering process at last, the sample sintering temperature is 1180～1250 ℃, is incubated 1～2 hour;
2) adopt wafer lapping machine coupled ion grinding process and chemical etching technology attenuate PMNT potter's material and detection electricity to give birth to fuel factor;
(1) after relaxation property PMNT ceramics sample was made, elder generation with the thick PMNT pottery of 1～3mm solid solution attenuate, reserved the thick surplus of 50 μ m with wafer lapping machine before reaching desired thickness;
(2) adopt the ion mill to be etched to desired thickness then; Ion mill etching technics parameter is: polar plate spacing 20mm, high frequency power 500W under the 10MHz, vacuum 0.13Pa, etching gas SF
6, gas flow 30～40mL/min, etch period 20～25min;
(3) remove sheet surface etching residue with aqueous medium ultrasonic cleaning mode, can obtain even bright and clean PMNT ceramic sheet;
(4) will go up the PMNT ceramic sheet polishing that a processing step makes, coat the polymethyl methacrylate photoresist with the dip-coating mode at the ceramic sheet edge;
(5) before 3 160～190 ℃/30min hot plates after baking technology and the photographic fixing of 1 isopropyl alcohol fixing solution, it is thick that the polymethyl methacrylate photoresist reaches 100～150nm approximately;
(6) adopting best mol proportioning is HCl/HF/NH
4F=1: 3: 15～20 mixed liquor obtains the ceramic sheet of the no undercutting phenomenon in surface as etching liquid, adopts the acetone rinsing at last, obtains bright and clean ceramic sheet;
(7) will go up the ceramics sample (13) that a processing step makes inserts in the plexiglass tent (11), adopt heat insulation support (14) and insulation and thermal insulation pad (16) as with the thermal insulation structure of base, by electrode (15) lead-in wire is drawn again, connect DZ2670A Hi-pot Tester (18) binding post, apply field intensity by the DZ2670A Hi-pot Tester, by the variations in temperature of infrared temperature probe (12) detection ferroelectric ceramics sheet, and by SCIT separate infrared hygrosensor displays temperature value;
3) the low-temperature eutectic ceramic process is made refrigeration structure;
(1) will go up the square sheet that PMNT ceramic sheet that a processing step makes divides homalographic into earlier; Evenly apply low-melting Sn silver slurry, the coating scope side of being slightly smaller than sheet area of containing again on square sheet two sides;
(2) folded to be incorporated in upper and lower surface and to fold up diameter between the two be 150～200 with square sheet) the Al/Cu alloy silk of μ m goes between;
(3) lamination layer that will be in then under the clamp position is inserted 300～400 ℃ of following pre-burning 10～15min in the resistance furnace; Insert 750～800 ℃ of following sintering 25～30min again, make to contain the abundant wetting coating of Sn silver slurry, and infiltrate ceramic interfacial layers;
(4) the multilayer refrigeration structure edge that makes of the last processing step of polishing is to prevent short circuit; The oxide layer of polishing electrode outlet line reaches prefluxing thereon;
(5) containing the thick polymethyl methacrylate photoresist of the about 100nm of Sn silver electrode surface employing spin coating proceeding coating up and down to eliminate electric spark;
(6) on the dual-in-line base, weld prepared refrigeration structure at last and form the little refrigerator of ferroelectric ceramics.
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| CN101734929B (en) * | 2009-12-13 | 2012-09-05 | 青岛大学 | Preparation method of pure-phase relaxation ferroelectric powder |
| CN102192614B (en) * | 2010-03-12 | 2012-11-07 | 香港理工大学 | Sheet-type micro refrigerator applying lead-free ferroelectric material |
| CN102455081B (en) * | 2010-10-20 | 2014-05-07 | 海洋王照明科技股份有限公司 | Electron tunneling-based refrigerator and LED lighting device using same |
| US20160076798A1 (en) * | 2014-09-15 | 2016-03-17 | Nascent Devices Llc | Methods to enhance the performance of electrocaloric dielectric polymer |
| US11300330B2 (en) * | 2016-06-27 | 2022-04-12 | Carrier Corporation | Electrocaloric heat transfer system |
| CN106382763B (en) * | 2016-09-09 | 2019-04-23 | 南京大学 | All solid state room temperature ferroelectric refrigerator based on thermal switch |
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