CA2065381A1 - Preparation of thin film ceramics by sol gel processing - Google Patents
Preparation of thin film ceramics by sol gel processingInfo
- Publication number
- CA2065381A1 CA2065381A1 CA002065381A CA2065381A CA2065381A1 CA 2065381 A1 CA2065381 A1 CA 2065381A1 CA 002065381 A CA002065381 A CA 002065381A CA 2065381 A CA2065381 A CA 2065381A CA 2065381 A1 CA2065381 A1 CA 2065381A1
- Authority
- CA
- Canada
- Prior art keywords
- sol
- mixed
- added
- alkoxide
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000000919 ceramic Substances 0.000 title claims abstract description 25
- 239000010409 thin film Substances 0.000 title description 11
- 238000002360 preparation method Methods 0.000 title description 7
- 238000003980 solgel method Methods 0.000 title description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims abstract description 42
- -1 zirconium alkoxide Chemical class 0.000 claims abstract description 22
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 21
- 239000010936 titanium Substances 0.000 claims abstract description 21
- 229960000583 acetic acid Drugs 0.000 claims abstract description 18
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000003381 stabilizer Substances 0.000 claims abstract description 15
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 15
- 229940046892 lead acetate Drugs 0.000 claims abstract description 14
- 229910052751 metal Inorganic materials 0.000 claims abstract description 12
- 239000002184 metal Substances 0.000 claims abstract description 12
- 239000012362 glacial acetic acid Substances 0.000 claims abstract description 11
- 150000003839 salts Chemical class 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 25
- 150000004703 alkoxides Chemical class 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- KQNKJJBFUFKYFX-UHFFFAOYSA-N acetic acid;trihydrate Chemical compound O.O.O.CC(O)=O KQNKJJBFUFKYFX-UHFFFAOYSA-N 0.000 claims description 10
- 239000002243 precursor Substances 0.000 claims description 8
- 239000002019 doping agent Substances 0.000 claims description 5
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 3
- 230000007062 hydrolysis Effects 0.000 claims description 2
- 238000006460 hydrolysis reaction Methods 0.000 claims description 2
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 claims 1
- 238000001556 precipitation Methods 0.000 abstract description 4
- 239000010408 film Substances 0.000 description 37
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 20
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 19
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 18
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 18
- 239000000243 solution Substances 0.000 description 18
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 14
- 229910052697 platinum Inorganic materials 0.000 description 10
- 230000005684 electric field Effects 0.000 description 9
- 238000004528 spin coating Methods 0.000 description 9
- 239000000758 substrate Substances 0.000 description 8
- 239000003153 chemical reaction reagent Substances 0.000 description 6
- XPGAWFIWCWKDDL-UHFFFAOYSA-N propan-1-olate;zirconium(4+) Chemical compound [Zr+4].CCC[O-].CCC[O-].CCC[O-].CCC[O-] XPGAWFIWCWKDDL-UHFFFAOYSA-N 0.000 description 6
- 125000003545 alkoxy group Chemical group 0.000 description 5
- 238000000137 annealing Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 238000007669 thermal treatment Methods 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- 229910052700 potassium Inorganic materials 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- ZHNUHDYFZUAESO-UHFFFAOYSA-N Formamide Chemical compound NC=O ZHNUHDYFZUAESO-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- 150000007942 carboxylates Chemical class 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910003781 PbTiO3 Inorganic materials 0.000 description 1
- 229910020698 PbZrO3 Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000008065 acid anhydrides Chemical class 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 244000309464 bull Species 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 150000001991 dicarboxylic acids Chemical class 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- XYIBRDXRRQCHLP-UHFFFAOYSA-N ethyl acetoacetate Chemical compound CCOC(=O)CC(C)=O XYIBRDXRRQCHLP-UHFFFAOYSA-N 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 150000002603 lanthanum Chemical class 0.000 description 1
- GJKFIJKSBFYMQK-UHFFFAOYSA-N lanthanum(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GJKFIJKSBFYMQK-UHFFFAOYSA-N 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 150000002763 monocarboxylic acids Chemical class 0.000 description 1
- ZTILUDNICMILKJ-UHFFFAOYSA-N niobium(v) ethoxide Chemical compound CCO[Nb](OCC)(OCC)(OCC)OCC ZTILUDNICMILKJ-UHFFFAOYSA-N 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 239000011369 resultant mixture Substances 0.000 description 1
- 238000000518 rheometry Methods 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 238000007761 roller coating Methods 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 238000010897 surface acoustic wave method Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 229910052713 technetium Inorganic materials 0.000 description 1
- 229910052716 thallium Inorganic materials 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/003—Titanates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
- C01G25/006—Compounds containing, besides zirconium, two or more other elements, with the exception of oxygen or hydrogen
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
- C04B35/49—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates containing also titanium oxides or titanates
- C04B35/491—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates containing also titanium oxides or titanates based on lead zirconates and lead titanates, e.g. PZT
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/077—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition
- H10N30/078—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by liquid phase deposition by sol-gel deposition
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/30—Three-dimensional structures
- C01P2002/34—Three-dimensional structures perovskite-type (ABO3)
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/853—Ceramic compositions
- H10N30/8548—Lead-based oxides
- H10N30/8554—Lead-zirconium titanate [PZT] based
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Ceramic Engineering (AREA)
- Manufacturing & Machinery (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Composite Materials (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Geology (AREA)
- Dispersion Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Inorganic Insulating Materials (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
2065381 9012755 PCTABS00002 A method of making a mixed sol to produce a titanate-based or zirconate-based ceramic. A metal salt such as lead acetate is dissolved in a stabilising agent such as glacial acetic acid, used in a concentration such that subsequent addition of titanium and zirconium alkoxide sols is effected without precipitation. PZT
ceramic films made from the mixed sols have: dielectric constant 150-4000; dielectric loss factor 0.001-0.08; saturation polarisation 0.8 µC/cm2.
ceramic films made from the mixed sols have: dielectric constant 150-4000; dielectric loss factor 0.001-0.08; saturation polarisation 0.8 µC/cm2.
Description
WO 90/127~ PCI'/GB90/00612 . 2~6 ~ 3 8 1 PREPARATION OF THIN FILM CERAMICS BY SOL GEL PROCESSING
This invention concerns a method of making a mixed sol of a composition to be gelled and heated to produce a titanate-based or a zirconate-based ceramic.
The invention is of particular interest in the preparation of thin films of the ceramic. Specific compositions comprise electronic ceramics such as PZT
(lead zirconate titanate), which have application in infra red detectors, surface acoustic wave devices, and particularly in electrooptic switching devices.
G. Yi et al (J. Appl. Phys. 64 (S), 1 September 1988, 2717 - 2723) described a method of making a sol for this purpose. The method involved dissolving lead acetate in acetic acid (using 1 ml of glacial acetic acid for each 29 of lead acetate trihydrate), adding zirconium propoxide and then adding titanium isopropoxide. The solution was agitated by mixing in an ultrasonic cleaner until all ,~
the condensed solid had dissolved. Ethylene glycol was then added in order to prevent cracking and to improve the surface smoothness of the film. In our hands, this method gave rise to several problems:
- Our attempts to achieve dissolution of the condensed solid that results when titanium alkoxides are added, were unsuccessful. In fact ultrasonic agitation was found to aggravate the problem.
Alkoxide condensates are inherently unstable, moisture sensitive, and hence precipitate irreversibly out of solution. Ultrasonification is therefore unlikely to effect redissolution of a precipitated alkoxide condensate.
- Ethylene glycol addition resulted in WO 90/1275; PCI/GB90/00612 206~381 further formation of condensed solid, in this instance associated with the presence of unreacted alkoxy groups.
- In common with all alkoxide derived feedstock materials for the preparation of ceramics, the resulting sols were unstable on storage.
This invention results from our attempts to overcome the problems associated with the aforesaid method. In one aspect the invention provides a method of making a mixed sol of a composition to be gelled and heated to produce a titanate-based or a zirconate-based ceramic, by forming a solution of at least one metal salt in a stabilising agent, adding to the solution a titanium alkoxide sol and/or a zirconium alkoxide sol to form a mixed sol precursor and adding water to form the mixed sol, characterised in that the amount of the stabilising agent used is sufficiently great to prevent turbidity when the alkoxide sol is added to the solution.
Titanate-based and zirconate-based ceramics are a known class of materials, including particularly the PZT ceramics which have a perovskite structure.
The formula of the ceramic is not a feature of the invention. The amounts of various metal solutions and sols can be chosen by known means to form a mixed sol of composition appropriate to produce the ceramic. In particular, dopant solutions and sols can be used in conventional manner.
When the ceramic contains Zr and Ti, the zirconium alkoxide sol is preferably added to the solution, prior to addition of the titanium alkoxide sol.
The prevention of condensation reaction resulting in turbidity can be achieved by the use of a variety of stabilising agents. These include monocarboxylic acids, generally Cl to C4 alkanoic '' ' ; , .: :
.
wos~/127~s ` P~T/G~90/00612 3 2~5381 acids such as acetic acid; dicarboxylic acids; acid anhydrides; glycols; chelating agents e.g. ethyl acetoacetate; and mixtures. In certain instances the addition of a separate solvent may be re~uired for complete stability and miscibility of chemical feed constituents.
The extent of the reaction between the stabilising agent and the titanium and zirconium alkoxides is uncertain, and it is convenient to define the concentration of the stabilising agent in terms of the lead (or other) salt. We prefer to use at least S moles e.g. 6.6 moles of stabilising agent (such as acetic acid) per mole of lead (or other) salt.
The at least one metal salt generally includes Pb which may be partly or indeed completely replaced by one or more of Ca, Sr, Ba, La, Mg, Na, K, Pb, Li, Cu, Au, Ag and Cd. The system may also :
include Al, Si, Na, K, Sc, V, Ga, Ge, As, Rb, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hj, Ta, W, Pt, Au, Hg, Tl, Bi, or a rare earth. The metal salts should be soluble in the chosen stabilising agent; for example, lead acetate is preferably used with acetic acid. The mixed sol may contain a dopant which may be a salt solution as indicated and/or an alkoxide sol of one or more of the above metals which sol may be added before or after the titanium and/or zirconium alkoxide sols.
The amount of the stabilising agent used needs to be sufficiently great to prevent turbidity, resulting from condensation, when the titanium or zirconium alkoxide sol is added to the solution. With acetic acid it is believed that some of the alkoxy groups in the partly condensed alkoxide sol are replaced by acetate ligands. The resulting alkoxy acetate condensate is then found to be stable to precipitation. (This work is published in the Journal r. , ~ . , '' , ' , , WO 90/127~5 2 0 ~ ~ 3 8 1 PCl /GB90/00612 of the American Ceramic Society 64 [5] 821-826 (1989) in an article by R. E. Riman, R. R. Landham, H. K.
Bowen entitled "Synthesis of uniform titanium and 1:1 stontium-titanium carboxyhydrosols by controlled hydrolysis of alkoxymetal carboxylate precursors).
Both titanium and zirconium sols comprise complexes of one metal atom with four alkoxide groups. Replacement of the first alkoxide group by carboxylate (such as acetate) is very easy, replacement of the second quite easy, of the third quite difficult, and of the fourth alkoxide group very difficult. ("Chemical Properties of metal alkoxides", chapter 1, p.202, in "Metal Alkoxides" editors D.C. Bradley, R.C. Mehrotra, D.P.
Gaur, Academic Press, 1978).
By way of example, at least 0.6 ml, e.g.
about 1 ml to about 3 ml of glacial acetic acid is preferably used per gram of lead acetate trihydrate.
The use of unnecessarily large quantities of acetic acid or other stabilising agent should be avoided, because it increases the amount of organic material that needs to be burnt out of the ceramic on firing.
To the dehydrated solution is added first the required amount of a zirconium alkoxide sol, followed by the required amount of a titanium alkoxide sol. The nature of the alkoxide is not critical;
typically alkoxides derived from Cl to C4 alkanols are used. The sols are added to the solution slowly with stirring to avoid localised precipitation, and preferably at temperatures not in excess of 80C, e.g.
3o in the range of 20-60C. The reagents should be as pure as possible, and steps should preferably be taken to eliminate Na, K and Li cations and 0 anions.
The resulting mixed sol preferably contains at least 5 moles e.g. at least 6.6 moles of acetate stabiliser per mole of lead salt and constitutes another aspect of this invention.
:;
.; , ~ ~ ;
:
WO90il2755 2 ~ 6 ~ 3 ~GBgo/006l2 s,~:
The resulting sol precursor is diluted with water to form the desired sol. Preferably the water is added in a mixture with an alcohol, again to avoid possible localised precipitation. Enough of this diluent is used to provide a stable sol of convenient application viscosity. Unreacted alkoxy groups are hydrolysed by the water, resulting in further controlled condensation.
Then a glycol, such as ethylene glycol, surfactants compatible with the sol or drying control chemical agents (DCCA's) [See D. R. Ulrich; Am. Ceram.
Soc. Bull., 64 [11] 1444-1448 (1985)] e.g. formamide and glycerol may be added to the sol in d concentration to improve its film-forming properties. Because unreacted alkoxy groups are no longer present, chemical reactions between alkoxy grouPs and the film forming additives do not take place, for example, the glycol addition does not result in formation of a condensed solid. The sol can be formed into a film on a non-porous surface by any convenient applica~ion technique such as flow or roller coating, brushing, spraying or particularly spin coating. Film thickness can be controlled by appropriate control of viscosity, feedstock dilution in alcohol and coating conditions.
Thin films less than 0.5 microns thick (before firing) may be prepared by a single application, thicker films can be prepared by multiple applications with ~-appropriate thermal treatment between applications.
Suitable non-porous surfaces include glass, platinum and titanium.
The films are first dried and then heated, e.g. to 300 to 700C, to burn out the organic species, this annealing treatment reduces the film thickness by up to 70~. To avoid cracking, the films are preferably heated at a rate of 1 - 20/min e.g. 5 - 15/min.
After annealing, the amorphous films are further heat ' ', . " r'' '' ,: ~ ' , ~' WO90/12755 ! PCT/GB90/00612 ~ 6~ 381 - 6 -treated to develop the desired crystalline phase, e.g.
tetragonal PZT. The appropriate thermal treatment in the temperature range 400 to ll50C imparts the required electrical characteristics in the film.
In another aspect the invention provides a PZT film of composition Pb ZrO O l o Tio O l O 3 0.4-0.6 TiC 6 0 4 03 with appropriate dopants where desired having the following electrical characteristics:
Dielectric constant l50 - 4000 Dielectric loss factor O.OOl - 0.08 Saturation polarisation O - 80 preferably
This invention concerns a method of making a mixed sol of a composition to be gelled and heated to produce a titanate-based or a zirconate-based ceramic.
The invention is of particular interest in the preparation of thin films of the ceramic. Specific compositions comprise electronic ceramics such as PZT
(lead zirconate titanate), which have application in infra red detectors, surface acoustic wave devices, and particularly in electrooptic switching devices.
G. Yi et al (J. Appl. Phys. 64 (S), 1 September 1988, 2717 - 2723) described a method of making a sol for this purpose. The method involved dissolving lead acetate in acetic acid (using 1 ml of glacial acetic acid for each 29 of lead acetate trihydrate), adding zirconium propoxide and then adding titanium isopropoxide. The solution was agitated by mixing in an ultrasonic cleaner until all ,~
the condensed solid had dissolved. Ethylene glycol was then added in order to prevent cracking and to improve the surface smoothness of the film. In our hands, this method gave rise to several problems:
- Our attempts to achieve dissolution of the condensed solid that results when titanium alkoxides are added, were unsuccessful. In fact ultrasonic agitation was found to aggravate the problem.
Alkoxide condensates are inherently unstable, moisture sensitive, and hence precipitate irreversibly out of solution. Ultrasonification is therefore unlikely to effect redissolution of a precipitated alkoxide condensate.
- Ethylene glycol addition resulted in WO 90/1275; PCI/GB90/00612 206~381 further formation of condensed solid, in this instance associated with the presence of unreacted alkoxy groups.
- In common with all alkoxide derived feedstock materials for the preparation of ceramics, the resulting sols were unstable on storage.
This invention results from our attempts to overcome the problems associated with the aforesaid method. In one aspect the invention provides a method of making a mixed sol of a composition to be gelled and heated to produce a titanate-based or a zirconate-based ceramic, by forming a solution of at least one metal salt in a stabilising agent, adding to the solution a titanium alkoxide sol and/or a zirconium alkoxide sol to form a mixed sol precursor and adding water to form the mixed sol, characterised in that the amount of the stabilising agent used is sufficiently great to prevent turbidity when the alkoxide sol is added to the solution.
Titanate-based and zirconate-based ceramics are a known class of materials, including particularly the PZT ceramics which have a perovskite structure.
The formula of the ceramic is not a feature of the invention. The amounts of various metal solutions and sols can be chosen by known means to form a mixed sol of composition appropriate to produce the ceramic. In particular, dopant solutions and sols can be used in conventional manner.
When the ceramic contains Zr and Ti, the zirconium alkoxide sol is preferably added to the solution, prior to addition of the titanium alkoxide sol.
The prevention of condensation reaction resulting in turbidity can be achieved by the use of a variety of stabilising agents. These include monocarboxylic acids, generally Cl to C4 alkanoic '' ' ; , .: :
.
wos~/127~s ` P~T/G~90/00612 3 2~5381 acids such as acetic acid; dicarboxylic acids; acid anhydrides; glycols; chelating agents e.g. ethyl acetoacetate; and mixtures. In certain instances the addition of a separate solvent may be re~uired for complete stability and miscibility of chemical feed constituents.
The extent of the reaction between the stabilising agent and the titanium and zirconium alkoxides is uncertain, and it is convenient to define the concentration of the stabilising agent in terms of the lead (or other) salt. We prefer to use at least S moles e.g. 6.6 moles of stabilising agent (such as acetic acid) per mole of lead (or other) salt.
The at least one metal salt generally includes Pb which may be partly or indeed completely replaced by one or more of Ca, Sr, Ba, La, Mg, Na, K, Pb, Li, Cu, Au, Ag and Cd. The system may also :
include Al, Si, Na, K, Sc, V, Ga, Ge, As, Rb, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hj, Ta, W, Pt, Au, Hg, Tl, Bi, or a rare earth. The metal salts should be soluble in the chosen stabilising agent; for example, lead acetate is preferably used with acetic acid. The mixed sol may contain a dopant which may be a salt solution as indicated and/or an alkoxide sol of one or more of the above metals which sol may be added before or after the titanium and/or zirconium alkoxide sols.
The amount of the stabilising agent used needs to be sufficiently great to prevent turbidity, resulting from condensation, when the titanium or zirconium alkoxide sol is added to the solution. With acetic acid it is believed that some of the alkoxy groups in the partly condensed alkoxide sol are replaced by acetate ligands. The resulting alkoxy acetate condensate is then found to be stable to precipitation. (This work is published in the Journal r. , ~ . , '' , ' , , WO 90/127~5 2 0 ~ ~ 3 8 1 PCl /GB90/00612 of the American Ceramic Society 64 [5] 821-826 (1989) in an article by R. E. Riman, R. R. Landham, H. K.
Bowen entitled "Synthesis of uniform titanium and 1:1 stontium-titanium carboxyhydrosols by controlled hydrolysis of alkoxymetal carboxylate precursors).
Both titanium and zirconium sols comprise complexes of one metal atom with four alkoxide groups. Replacement of the first alkoxide group by carboxylate (such as acetate) is very easy, replacement of the second quite easy, of the third quite difficult, and of the fourth alkoxide group very difficult. ("Chemical Properties of metal alkoxides", chapter 1, p.202, in "Metal Alkoxides" editors D.C. Bradley, R.C. Mehrotra, D.P.
Gaur, Academic Press, 1978).
By way of example, at least 0.6 ml, e.g.
about 1 ml to about 3 ml of glacial acetic acid is preferably used per gram of lead acetate trihydrate.
The use of unnecessarily large quantities of acetic acid or other stabilising agent should be avoided, because it increases the amount of organic material that needs to be burnt out of the ceramic on firing.
To the dehydrated solution is added first the required amount of a zirconium alkoxide sol, followed by the required amount of a titanium alkoxide sol. The nature of the alkoxide is not critical;
typically alkoxides derived from Cl to C4 alkanols are used. The sols are added to the solution slowly with stirring to avoid localised precipitation, and preferably at temperatures not in excess of 80C, e.g.
3o in the range of 20-60C. The reagents should be as pure as possible, and steps should preferably be taken to eliminate Na, K and Li cations and 0 anions.
The resulting mixed sol preferably contains at least 5 moles e.g. at least 6.6 moles of acetate stabiliser per mole of lead salt and constitutes another aspect of this invention.
:;
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:
WO90il2755 2 ~ 6 ~ 3 ~GBgo/006l2 s,~:
The resulting sol precursor is diluted with water to form the desired sol. Preferably the water is added in a mixture with an alcohol, again to avoid possible localised precipitation. Enough of this diluent is used to provide a stable sol of convenient application viscosity. Unreacted alkoxy groups are hydrolysed by the water, resulting in further controlled condensation.
Then a glycol, such as ethylene glycol, surfactants compatible with the sol or drying control chemical agents (DCCA's) [See D. R. Ulrich; Am. Ceram.
Soc. Bull., 64 [11] 1444-1448 (1985)] e.g. formamide and glycerol may be added to the sol in d concentration to improve its film-forming properties. Because unreacted alkoxy groups are no longer present, chemical reactions between alkoxy grouPs and the film forming additives do not take place, for example, the glycol addition does not result in formation of a condensed solid. The sol can be formed into a film on a non-porous surface by any convenient applica~ion technique such as flow or roller coating, brushing, spraying or particularly spin coating. Film thickness can be controlled by appropriate control of viscosity, feedstock dilution in alcohol and coating conditions.
Thin films less than 0.5 microns thick (before firing) may be prepared by a single application, thicker films can be prepared by multiple applications with ~-appropriate thermal treatment between applications.
Suitable non-porous surfaces include glass, platinum and titanium.
The films are first dried and then heated, e.g. to 300 to 700C, to burn out the organic species, this annealing treatment reduces the film thickness by up to 70~. To avoid cracking, the films are preferably heated at a rate of 1 - 20/min e.g. 5 - 15/min.
After annealing, the amorphous films are further heat ' ', . " r'' '' ,: ~ ' , ~' WO90/12755 ! PCT/GB90/00612 ~ 6~ 381 - 6 -treated to develop the desired crystalline phase, e.g.
tetragonal PZT. The appropriate thermal treatment in the temperature range 400 to ll50C imparts the required electrical characteristics in the film.
In another aspect the invention provides a PZT film of composition Pb ZrO O l o Tio O l O 3 0.4-0.6 TiC 6 0 4 03 with appropriate dopants where desired having the following electrical characteristics:
Dielectric constant l50 - 4000 Dielectric loss factor O.OOl - 0.08 Saturation polarisation O - 80 preferably
2 - 40 ~C/cm2.
The film may have a polarisation electric field hysteresis loop showing high remanent polarisation, high saturation polarisation with the difference between the saturation and the remanent polarisation being small and preferably not greater than half the value of the saturation polarisation. Dielectric loss factor should be measured on a high quality electrode comprising a silicon wafer with successive sputtered coatings of titanium and platinum beneath the PZ~ film.
The thin film can either behave as a ferroelectric and be used for switching, capacitor or for electromechanical coupling applications, or alternatively, the thin film can be non-ferroelectric and be used as a passive dielectric layer.
The invention gives rise to the following advantages:
a) Currently used techniques for the preparation of thin films on a range of substrates such as silicon or quartz, are sputtering, MOCVD, chemical vapour deposition and plasma vapour deposition. The problems associated with these techniques are high capital costs, difficult processing controls. use of expensive precursors, low , , :, .
,. . : . . . .
, : , .: , .. : ~ ~ , ~ 7 ~ 2 06~3 ~
through-put and size limitations. The use of sol-gel processing solves most of these problems in that the equipment needed is inexpensive, processing control is easy leading to a homogeneous product, precursors are inexpensive and no problems arise regarding through-put or size. -b) Existing sol gel techniques for the preparation of thin films suffer from the problems that the feeds are generally irreproducible and have a short shelf-life and that the properties of the films produced from the feeds vary considerably and are for that reason unacceptable. Sols made according to the present invention have reproducible compositions and long shelf-lives, e.g. two months or more.
Reference is directed to the accompanying drawing which is a flow diagram for preparation of PZT
feed.
Example 1 A mixed sol, of a composition to be gelled and heated to produce a PZT ceramic material, was prepared as shown in the flow diagram of Figure l.
Crack free films of this mixed sol were deposited on glass, platinum and titanium by standard spin coating techniques. The deposited films were annealed under the following conditions:
Heat at lC per minute to 600C; hold for 2 hours at 600C; cool to room temperature at lC per minute. This anneal was effective to burn out organics. After annealing, the amorphous films were further heat treated to develop the desired crystalline phase, tetragonal PZT. The appropriate thermal treatment in the range 650 - l150C imparted the required electrical characteristics in the film.
The electrical properties of a typical PZT
( b ZrO.52 Tio.48 3) formed by the above method were as follows:
, ........ ~ -: : . ............. : , . . i .: ~
woso/l2755 PCT/GB90/00612 ~ 0 6 ~
Dielectric constant (epsilon) - 250 Loss Factor (tan delta) - 0.022 Saturation Polarisation (PS) - 7~C/cm2 Switching time - 54 ns with a polarisation-electric field hysteresis loop that is symmetrical about the polarisation-electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
These results are consistently better than any previously reported for spin-coated sol-gel derived films. For example, in the aforementioned paper, Yi et al reported that their ceramic had a loss factor of 0.1 - 0.7. These higher values preclude the use of such films in many intended applications, for which films according to the present invention are suitable.
Example 2 A mixed sol of a composition to be gelled and heated to produce a PZT ceramic material was prepared as follows. 309 of lead acetate trihydrate was dissolved in 36 mls of glacial acetic acid at 80C.
The solution was then cooled to room temperature.
17.769 of zirconium n-propoxide (70% solution in n-propanol) was added slowly to the solution and withstirring. 11.619 of titanium iso-propoxide was then added to the resultant mixture with stirring in order to form the PZT sol. lS mls of water was then added to the sol with stirring, and finally 4.39 of ethylene glycol was added to complete the sol formation. Prior to spin coating, tne sol was diluted to achieve the desired rheology for spin coating onto a substrate. To dilute the sol, 99 of sol was added to 69 of a n-propanol/water mixture, the composition of the n-propanol/water mixture being 82.5 wtg n-propanol, 17.5 wt% water. The diluted sol was then spin coated at . . . ..
,. : ~: :, ., . i : .-' '; 206~381 1000 rpm for 12 secs onto a platinum coated substrate to form a thin film. The deposited films were annealed under the following conditions:-Heat at 10/min to 400C, hold for 1 minute then cool to room temperature. This anneal waseffective to burn out organics. After annealing, the amorphous films were further heat treated to develop the desired perovskite crystalline phase. The appropriate thermal treatment in the range 400 - 1150C imparted the required electrical characteristics in the film.
The properties of a typical PZT film (Pb ZrO 48 Tio 52 3) formed by the above method were as follows:-Dielectric constant (epsilon) - 870 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.025 Saturation Polarisation at 5Y, Ps - 30 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 3 A mixed sol to be gelled and heated to produce a PZT ceramic of composition Pb ZrO 40 Tio 60 3 was prepared by following the -~
method of Example 2 with the quantities of alkoxides adjusted accordingly. In this example the amounts of reagents used was as follows:-36 mls glacial acetic acid 309 lead acetate trihydrate 14.799 zirconium n-propoxide (70~ solution in n-propanol) 13.479 titanium iso-propoxide 15 mls water 4.39 ethylene glycol . ~
;. ' .. : . , . ~ ,... . .. . .. . . . ... . . .
~206538~
The sol produced was diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lO00 rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2.
The properties of a typical PZT film of composition Pb ZrO 4 Tio 6 3 formed by the above method were as follows:-Dielectric constant (epsilon) - 660 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 30 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 4 A mixed sol to be gelled and heated to produce a PZT ceramic of composition Pbo.97 LaO.33 (ZrO.3 Tio.7)0 9925 3 was prepared by following the method of Example 2 with the quantities of alkoxides adjusted accordingly, and with a lanthanum salt being dissolved in the glacial acetic acid after the lead acetate trihydrate addition but before the addition of the alkoxides. In this example the amounts of reagents used were as follows:-36 mls glacial acetic acid 29.lg lead acetate trihydrate 1.039 lanthanum nitrate hexahydrate ll.Olg zirconium n-propoxide (70~ solution in n-propanol) l5.60g titanium iso-propoxide l5 mls water 4.39 ethylene glycol The sol produced was diluted as described in WO 90/127~5 PCI'/GB90/00612 - '', ;,-~'~06~381 Example 2 prior to spin coating on a platinum coated substrate at 1000 rpm for 12 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2.
The properties of a typical PZT film of composition Pbo 97 LaO 33 (ZrO.3 Tio.7)0.9925 3 by the above methods were as follows:-Dielectric constant (epsilon) - 780 at S volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 20 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 5 A mixed sol to be gelled and heated to produce a PZT ceramic of composition 0.985 (Zro.3 TiQ.7)0.g7 Nbo 03 3 was prepared by following the method of Example 2 with the quantities of zirconium and titanium alkoxides adjusted accordingly, and with a niobium alkoxide dissolved in n-propanol being added to the sol after the titanium iso propoxide addition but before the addition of water and ethylene glycol. In this example the amounts of reagents used were as follows:-36 mls glacial acetic acid 29.539 lead acetate trihydrate 10.759 zirconium n-propoxide (70% solution in n-propanol) 15.259 titanium iso-propoxide 0.759 niobium ethoxide dissolved in 5 mls n-propanol
The film may have a polarisation electric field hysteresis loop showing high remanent polarisation, high saturation polarisation with the difference between the saturation and the remanent polarisation being small and preferably not greater than half the value of the saturation polarisation. Dielectric loss factor should be measured on a high quality electrode comprising a silicon wafer with successive sputtered coatings of titanium and platinum beneath the PZ~ film.
The thin film can either behave as a ferroelectric and be used for switching, capacitor or for electromechanical coupling applications, or alternatively, the thin film can be non-ferroelectric and be used as a passive dielectric layer.
The invention gives rise to the following advantages:
a) Currently used techniques for the preparation of thin films on a range of substrates such as silicon or quartz, are sputtering, MOCVD, chemical vapour deposition and plasma vapour deposition. The problems associated with these techniques are high capital costs, difficult processing controls. use of expensive precursors, low , , :, .
,. . : . . . .
, : , .: , .. : ~ ~ , ~ 7 ~ 2 06~3 ~
through-put and size limitations. The use of sol-gel processing solves most of these problems in that the equipment needed is inexpensive, processing control is easy leading to a homogeneous product, precursors are inexpensive and no problems arise regarding through-put or size. -b) Existing sol gel techniques for the preparation of thin films suffer from the problems that the feeds are generally irreproducible and have a short shelf-life and that the properties of the films produced from the feeds vary considerably and are for that reason unacceptable. Sols made according to the present invention have reproducible compositions and long shelf-lives, e.g. two months or more.
Reference is directed to the accompanying drawing which is a flow diagram for preparation of PZT
feed.
Example 1 A mixed sol, of a composition to be gelled and heated to produce a PZT ceramic material, was prepared as shown in the flow diagram of Figure l.
Crack free films of this mixed sol were deposited on glass, platinum and titanium by standard spin coating techniques. The deposited films were annealed under the following conditions:
Heat at lC per minute to 600C; hold for 2 hours at 600C; cool to room temperature at lC per minute. This anneal was effective to burn out organics. After annealing, the amorphous films were further heat treated to develop the desired crystalline phase, tetragonal PZT. The appropriate thermal treatment in the range 650 - l150C imparted the required electrical characteristics in the film.
The electrical properties of a typical PZT
( b ZrO.52 Tio.48 3) formed by the above method were as follows:
, ........ ~ -: : . ............. : , . . i .: ~
woso/l2755 PCT/GB90/00612 ~ 0 6 ~
Dielectric constant (epsilon) - 250 Loss Factor (tan delta) - 0.022 Saturation Polarisation (PS) - 7~C/cm2 Switching time - 54 ns with a polarisation-electric field hysteresis loop that is symmetrical about the polarisation-electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
These results are consistently better than any previously reported for spin-coated sol-gel derived films. For example, in the aforementioned paper, Yi et al reported that their ceramic had a loss factor of 0.1 - 0.7. These higher values preclude the use of such films in many intended applications, for which films according to the present invention are suitable.
Example 2 A mixed sol of a composition to be gelled and heated to produce a PZT ceramic material was prepared as follows. 309 of lead acetate trihydrate was dissolved in 36 mls of glacial acetic acid at 80C.
The solution was then cooled to room temperature.
17.769 of zirconium n-propoxide (70% solution in n-propanol) was added slowly to the solution and withstirring. 11.619 of titanium iso-propoxide was then added to the resultant mixture with stirring in order to form the PZT sol. lS mls of water was then added to the sol with stirring, and finally 4.39 of ethylene glycol was added to complete the sol formation. Prior to spin coating, tne sol was diluted to achieve the desired rheology for spin coating onto a substrate. To dilute the sol, 99 of sol was added to 69 of a n-propanol/water mixture, the composition of the n-propanol/water mixture being 82.5 wtg n-propanol, 17.5 wt% water. The diluted sol was then spin coated at . . . ..
,. : ~: :, ., . i : .-' '; 206~381 1000 rpm for 12 secs onto a platinum coated substrate to form a thin film. The deposited films were annealed under the following conditions:-Heat at 10/min to 400C, hold for 1 minute then cool to room temperature. This anneal waseffective to burn out organics. After annealing, the amorphous films were further heat treated to develop the desired perovskite crystalline phase. The appropriate thermal treatment in the range 400 - 1150C imparted the required electrical characteristics in the film.
The properties of a typical PZT film (Pb ZrO 48 Tio 52 3) formed by the above method were as follows:-Dielectric constant (epsilon) - 870 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.025 Saturation Polarisation at 5Y, Ps - 30 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 3 A mixed sol to be gelled and heated to produce a PZT ceramic of composition Pb ZrO 40 Tio 60 3 was prepared by following the -~
method of Example 2 with the quantities of alkoxides adjusted accordingly. In this example the amounts of reagents used was as follows:-36 mls glacial acetic acid 309 lead acetate trihydrate 14.799 zirconium n-propoxide (70~ solution in n-propanol) 13.479 titanium iso-propoxide 15 mls water 4.39 ethylene glycol . ~
;. ' .. : . , . ~ ,... . .. . .. . . . ... . . .
~206538~
The sol produced was diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lO00 rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2.
The properties of a typical PZT film of composition Pb ZrO 4 Tio 6 3 formed by the above method were as follows:-Dielectric constant (epsilon) - 660 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 30 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 4 A mixed sol to be gelled and heated to produce a PZT ceramic of composition Pbo.97 LaO.33 (ZrO.3 Tio.7)0 9925 3 was prepared by following the method of Example 2 with the quantities of alkoxides adjusted accordingly, and with a lanthanum salt being dissolved in the glacial acetic acid after the lead acetate trihydrate addition but before the addition of the alkoxides. In this example the amounts of reagents used were as follows:-36 mls glacial acetic acid 29.lg lead acetate trihydrate 1.039 lanthanum nitrate hexahydrate ll.Olg zirconium n-propoxide (70~ solution in n-propanol) l5.60g titanium iso-propoxide l5 mls water 4.39 ethylene glycol The sol produced was diluted as described in WO 90/127~5 PCI'/GB90/00612 - '', ;,-~'~06~381 Example 2 prior to spin coating on a platinum coated substrate at 1000 rpm for 12 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2.
The properties of a typical PZT film of composition Pbo 97 LaO 33 (ZrO.3 Tio.7)0.9925 3 by the above methods were as follows:-Dielectric constant (epsilon) - 780 at S volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 20 ~C/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 5 A mixed sol to be gelled and heated to produce a PZT ceramic of composition 0.985 (Zro.3 TiQ.7)0.g7 Nbo 03 3 was prepared by following the method of Example 2 with the quantities of zirconium and titanium alkoxides adjusted accordingly, and with a niobium alkoxide dissolved in n-propanol being added to the sol after the titanium iso propoxide addition but before the addition of water and ethylene glycol. In this example the amounts of reagents used were as follows:-36 mls glacial acetic acid 29.539 lead acetate trihydrate 10.759 zirconium n-propoxide (70% solution in n-propanol) 15.259 titanium iso-propoxide 0.759 niobium ethoxide dissolved in 5 mls n-propanol
3, 15 mls water
4.39 ethylene glycol WO90/127iS PCT/GB90/00612 ~ 0~5~8~ - 12 - --The sol produced was diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lO00 rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2.
The properties of a typical PZT film of composition Pbo 985 (ZrO 3 Tio.7)0-97 Nbo.03 3 for e by the above methods were as follows:-Dielectric constant (epsilon) - 450 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 20 ~c/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 6 A mixed sol to be gelled and heated to produce a lead zirconate (PZ) ceramic of composition PbZrO3 was prepared by following the method of Example 2 with the appropriate quantity of zirconium alkoxide added and with no titanium alkoxide being added at all.
In this example the amounts of reagents used was as follows:
36 mls glacial acetic acid 309 lead acetate trihydrate 36.979 zirconium n-propoxide (70% solution in n-propanol) 15 mls water 4.39 ethylene glycol The sol produced was diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lO00 rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2 to give a . ~ , . . .
Wo90/12755 PCT/GB90/00612 l3 2~65381 lead zirconate thin film. ~ ..
Example 7 A mixed sol to be gelled and heated to produce a lead titanate (PT) ceramic of composition PbTiO3 was prepared by following the method of Example 2 with the appropriate quantity of titanium alkoxide added and with no zirconium alkoxide being added at ~ .
all. In this example the amounts of reagents used was as follows:-36 mls glacial acetic acid 309 lead acetate trihydrate 22.469 titanium iso-propoxide lS mls water 4.39 ethylene glycol The sol produced ~as diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lOOO rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2 to give a lead titanate thin film.
~ . , . . ... . , ~. .
- , . ~, . .: ~ , .
- , .. .:. :.
.. . . ..
. i' ' ' :
- : ~ . :
The properties of a typical PZT film of composition Pbo 985 (ZrO 3 Tio.7)0-97 Nbo.03 3 for e by the above methods were as follows:-Dielectric constant (epsilon) - 450 at 5 volts Film thickness - 2300R
Loss factor (tan delta) - 0.02 Saturation Polarisation at 5V, PS ~ 20 ~c/cm2 with a polarisation - electric field hysteresis loop that is symmetrical about the polarisation - electric field origin showing a difference between the saturation and remanent polarisation of less than half the value of the saturation polarisation.
Example 6 A mixed sol to be gelled and heated to produce a lead zirconate (PZ) ceramic of composition PbZrO3 was prepared by following the method of Example 2 with the appropriate quantity of zirconium alkoxide added and with no titanium alkoxide being added at all.
In this example the amounts of reagents used was as follows:
36 mls glacial acetic acid 309 lead acetate trihydrate 36.979 zirconium n-propoxide (70% solution in n-propanol) 15 mls water 4.39 ethylene glycol The sol produced was diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lO00 rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2 to give a . ~ , . . .
Wo90/12755 PCT/GB90/00612 l3 2~65381 lead zirconate thin film. ~ ..
Example 7 A mixed sol to be gelled and heated to produce a lead titanate (PT) ceramic of composition PbTiO3 was prepared by following the method of Example 2 with the appropriate quantity of titanium alkoxide added and with no zirconium alkoxide being added at ~ .
all. In this example the amounts of reagents used was as follows:-36 mls glacial acetic acid 309 lead acetate trihydrate 22.469 titanium iso-propoxide lS mls water 4.39 ethylene glycol The sol produced ~as diluted as described in Example 2 prior to spin coating on a platinum coated substrate at lOOO rpm for l2 seconds. The deposited films were then annealed and further heat treated under the same conditions described in Example 2 to give a lead titanate thin film.
~ . , . . ... . , ~. .
- , . ~, . .: ~ , .
- , .. .:. :.
.. . . ..
. i' ' ' :
- : ~ . :
Claims (11)
1. A method of making a mixed sol of a composition to be gelled and heated to produce a titanate-based or a zirconate-based ceramic, by forming a solution of at least one metal salt in a stabilising agent, adding to the solution a titanium alkoxide sol and/or a zirconium alkoxide sol to form a mixed sol precursor and adding water to form the mixed sol, characterised in that the amount of the stabilising agent used is sufficiently great to prevent turbidity when the alkoxide sol is added to the solution.
2. A method as claimed in Claim 1, wherein the stabilising agent is acetic acid.
3. A method as claimed in Claim 2, wherein the metal salt is lead acetate.
4. A method as claimed in Claim 3, wherein at least 0.6 ml of glacial acetic acid is used per gram of lead acetate trihydrate.
5. A method as claimed in any one of Claims l to 4, wherein the zirconium alkoxide sol is added to the solution prior to addition of the titanium alkoxide sol.
6. A method as claimed in any one of Claims 1 to 5, wherein water mixed with an alcohol is added to the sol precursor.
7. A method as claimed in any one of Claims l to 6, wherein an alkoxide sol of at least one metal other than titanium and zirconium is also added to form the mixed sol.
8. A method as claimed in Claim 7 wherein, after hydrolysis of metal-alkoxy groups in the sol precursor, a glycol is added to the mixed sol in a concentration to improve its film-forming properties.
9. A method as claimed in any one of Claims 1 to 8, wherein the mixed sol is formed into a film on a non-porous surface and the film is heated to produce the desired titanate-based ceramic.
10. A PZT film of composition Pb Zr0.0-1.0 Ti0.0-1.0 03 with appropriate dopants where desired having the following electrical characteristics:
Dielectric constant l50 - 4000 Dielectric loss factor 0.001 - 0.08 Saturation polarisation 0 - 80 µC/cm2
Dielectric constant l50 - 4000 Dielectric loss factor 0.001 - 0.08 Saturation polarisation 0 - 80 µC/cm2
11. A mixed sol of a composition to be gelled and heated to produce a PZT ceramic of composition Pb Zr0.0-1.0 Ti0.0-1.0 03 with appropriate dopants where required, comprising at least 5 moles of acetate stabiliser per mole of lead salt.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8909107.8 | 1989-04-21 | ||
GB898909107A GB8909107D0 (en) | 1989-04-21 | 1989-04-21 | Preparation of thin film ceramics by sol gel processing |
GB8910717.1 | 1989-05-10 | ||
GB898910717A GB8910717D0 (en) | 1989-05-10 | 1989-05-10 | Gel processing method |
Publications (1)
Publication Number | Publication Date |
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CA2065381A1 true CA2065381A1 (en) | 1990-10-22 |
Family
ID=26295255
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002065381A Abandoned CA2065381A1 (en) | 1989-04-21 | 1990-04-20 | Preparation of thin film ceramics by sol gel processing |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0469053A1 (en) |
JP (1) | JPH04506791A (en) |
KR (1) | KR920701048A (en) |
AU (1) | AU5548290A (en) |
CA (1) | CA2065381A1 (en) |
WO (1) | WO1990012755A1 (en) |
Families Citing this family (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE1004604A4 (en) * | 1990-11-08 | 1992-12-22 | Solvay | Manufacturing method of mixed metal oxide powder. |
JPH04259380A (en) * | 1991-02-13 | 1992-09-14 | Mitsubishi Materials Corp | Method for controlling crystalline orientation property of pzt ferroelectric body thin film |
JPH0773732A (en) * | 1993-06-23 | 1995-03-17 | Sharp Corp | Dielectric thin film element and its manufacture |
DE4332831C1 (en) * | 1993-09-27 | 1994-10-06 | Fraunhofer Ges Forschung | Shaped bodies based on PZT(Pb(Zr, Ti)O3, lead zirconate - lead titanate), process and intermediate for the production thereof |
JPH07130232A (en) * | 1993-11-04 | 1995-05-19 | Fuji Xerox Co Ltd | Manufacture of conductive thin film |
EP0727832B1 (en) * | 1995-02-20 | 2001-11-28 | Seiko Epson Corporation | Method of producning a piezoelectric thin film |
EP0736915A1 (en) * | 1995-04-03 | 1996-10-09 | Seiko Epson Corporation | Piezoelectric thin film, method for producing the same, and ink jet recording head using the thin film |
JP3207206B2 (en) * | 1996-07-17 | 2001-09-10 | シチズン時計株式会社 | Ferroelectric element and method of manufacturing the same |
GB9909375D0 (en) * | 1999-04-24 | 1999-06-23 | Secr Defence | Improvements in or relating to sol gel processing of lead zirconate titanate thin films |
KR100408517B1 (en) | 2000-12-28 | 2003-12-06 | 삼성전자주식회사 | Manufacturing method for ferroelectric thin film using sol-gel process |
KR100416760B1 (en) * | 2001-03-12 | 2004-01-31 | 삼성전자주식회사 | Method for preparing a thick coating of PZT using sol-gel process |
CA2386380A1 (en) * | 2002-05-27 | 2003-11-27 | Mohammed Saad | Heavy metal oxide thin film, active and passive planar waveguides and optical devices |
US7229662B2 (en) * | 2003-12-16 | 2007-06-12 | National University Of Singapore | Heterolayered ferroelectric thin films and methods of forming same |
JP4803401B2 (en) * | 2004-05-31 | 2011-10-26 | セイコーエプソン株式会社 | Method for manufacturing ferroelectric film |
JP4709544B2 (en) * | 2004-05-31 | 2011-06-22 | セイコーエプソン株式会社 | Precursor composition, precursor composition manufacturing method, ferroelectric film manufacturing method, piezoelectric element, semiconductor device, piezoelectric actuator, ink jet recording head, and ink jet printer |
US20100285320A1 (en) * | 2004-11-26 | 2010-11-11 | Mohammed Saad | Amorphous thin films and method of manufacturing same |
JP4269172B2 (en) * | 2004-12-24 | 2009-05-27 | セイコーエプソン株式会社 | Ink for inkjet coating, method for producing the same, and method for producing a ferroelectric film |
EP1675162A3 (en) | 2004-12-27 | 2007-05-30 | Seiko Epson Corporation | Ferroelectric film, method of manufacturing ferroelectric film, ferroelectric capacitor, and ferroelectric memory |
JP4543985B2 (en) * | 2005-03-24 | 2010-09-15 | セイコーエプソン株式会社 | Lead zirconate titanate niobate laminate |
JP2007145672A (en) * | 2005-11-29 | 2007-06-14 | Seiko Epson Corp | Raw material composition for multiple metal oxide |
US8623737B2 (en) * | 2006-03-31 | 2014-01-07 | Intel Corporation | Sol-gel and mask patterning for thin-film capacitor fabrication, thin-film capacitors fabricated thereby, and systems containing same |
JP6442860B2 (en) * | 2014-04-23 | 2018-12-26 | 株式会社リコー | Precursor sol-gel solution, electromechanical transducer, droplet discharge head, and ink jet recording apparatus |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US3331659A (en) * | 1964-03-31 | 1967-07-18 | Malloy Frank | Process for producing lead titanate powder |
FR2571713B1 (en) * | 1984-10-15 | 1990-03-23 | Centre Nat Rech Scient | PROCESS FOR THE PREPARATION OF TITANATES, ZIRCONATES AND STANNATES |
-
1990
- 1990-04-20 WO PCT/GB1990/000612 patent/WO1990012755A1/en not_active Application Discontinuation
- 1990-04-20 KR KR1019910701367A patent/KR920701048A/en not_active Application Discontinuation
- 1990-04-20 AU AU55482/90A patent/AU5548290A/en not_active Abandoned
- 1990-04-20 CA CA002065381A patent/CA2065381A1/en not_active Abandoned
- 1990-04-20 EP EP90907212A patent/EP0469053A1/en not_active Withdrawn
- 1990-04-20 JP JP2506646A patent/JPH04506791A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
WO1990012755A1 (en) | 1990-11-01 |
AU5548290A (en) | 1990-11-16 |
JPH04506791A (en) | 1992-11-26 |
KR920701048A (en) | 1992-08-11 |
EP0469053A1 (en) | 1992-02-05 |
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