US5091348A
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Sol-gel method of making ceramics
Assignee: Rio Tinto Alcan International Ltd
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Filing: 1989-04-17
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Granted: 1992-02-25
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Expires: 2009-04-17
Abstract
Abstract The invention concerns sol-gel techniques for making PZT-type ceramics having a perovskite-type structure and ferrite ceramics having a spinel-type structure. Colloidal hydrated oxide sols are mixed with metal salt solutions in the required concentration and the mixed sols dehydrated to form homogeneous gels which are fired at 250° C.-650° C., pressed and sintered at 900°-1300° C. The resulting ceramics include PZT4, PZT5 and lithium ferrites. These have excellent homogeneity, small grain size, high density and improved electrical properties, particularly low dielectric loss, compared with known ceramics of similar composition.
Inventors
- 👤 James L. Woodhead
- 👤 Paul Groves
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 17:35
CPC Classifications
C; C04; C04B; C04B33/00; C04B33/02; H; H10; H10N; H10N30/00; H10N30/01; H10N30/07; H10N30/074; H10N30/077; H10N30/078; C01; C01G; C01G23/00; C01G23/003; C01G25/00; C01G25/006; C01G49/00; C01G49/0018; C04B35/00; C04B35/01; C04B35/26; C04B35/2608; C04B35/2616; C04B35/48; C04B35/49; C04B35/491; C01P; C01P2002/00; C01P2002/30; C01P2002/32; C01P2002/34; C01P2002/80; C01P2002/88; C01P2004/00; C01P2004/30; C01P2004/32; C01P2004/60; C01P2004/61; C01P2006/00; C01P2006/10; H10N30/80; H10N30/85; H10N30/853; H10N30/8548; H10N30/8554
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
127 words
A method of making a titanate ceramic material having a perovskite structure comprising mixing a first sol selected from the group consisting of hydrated titanium oxide sol and hydrated zirconium oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), iron (III), aluminium (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), with the proviso that the first and second sols are not the same, wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 2
Independent Claim
127 words
A method of making a titanate ceramic material having a perovskite structure comprising mixing a first sol selected from the group consisting of hydrated titanium oxide sol and hydrated zirconium oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), iron (III), aluminium (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), with the proviso that the first and second sols are not the same, wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 3
Dependent Claim
25 words
A method as claimed in claim 1, wherein the first sol is a hydrated titania sol and the second sol is a hydrated zirconia sol.
Claim 4
Dependent Claim
114 words
A method as claimed in claim 1, wherein the first sol is mixed with the second sol and with a solution of a salt of at least one metal selected from the group consisting of Pb, Ca, Sr, Ba, La, Rb, Ag, Au, Cd, Na, Mg, Li, K, Sc, V, Cr, Mn, Fe, Co, Y, Nb, In, Hf, Ta, W, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U, Ni, Cu, Zn, As, Ga, Ge, Ru and Sn, wherein the first and second sols and the metal salt solution are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic.
Claim 5
Dependent Claim
43 words
A method as claimed in claim 3, wherein a hydrated titania sol is mixed with a hydrated zirconia sol and a solution of a lead salt in proportions to form a mixed sol having a composition corresponding to that of a PZT ceramic.
Claim 6
Dependent Claim
41 words
A method as claimed in claim 4, wherein there is included in the mixture at least one further metal salt solution wherein the metal is selected from Ca, Sr, Ba, La, Mg, Na, K, Rb, Li, Cu, Ag, Au and Cd.
Claim 7
Dependent Claim
16 words
A method as claimed in claim 1, wherein the mixed sol is dehydrated by spray drying.
Claim 8
Dependent Claim
28 words
A method as claimed in claim 1, wherein the gel is heated to form the ceramic material by dissociation, compound formation or polymorphic transformation of the mixed components.
Claim 9
Dependent Claim
27 words
A method as claimed in claim 1, wherein the gel is heated at a temperature of from 250° C. to 650° C. to form the ceramic material.
Claim 10
Dependent Claim
15 words
A method as claimed in claim 1, wherein the ceramic material is pressed and sintered.
Claim 11
Dependent Claim
26 words
A PZT4 ceramic made by the method of claim 1 and having the following properties: density--at least 95% dielectric constant--1050-1250 loss factor--less than 0.002 coupling co-efficient--0.53-0.60.
Claim 12
Dependent Claim
29 words
A PZT5 ceramic made by the method of claim 1 and having the following properties. density--at least 95% piezoelectric coefficient--50-160 coupling coefficient--0.55-0.65 dielectric constant--800-1600 loss factor--0.001-0.025 figure of merit--50-1000.
Claim 13
Independent Claim
176 words
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), and with a solution of a salt of at least one metal selected from the group consisting of Li, Mg, Mn, Zn, Cu, Ni, Co, Cr, Ba, Sr, Pb, Al, Si, Na, K, Sc, Ti, V, Ga, Ge, As, Rb, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hf, Ta, W, Pt, Au, Hg, Tl, Bi or a rare earth, wherein the first and second sols and the metal salt solution are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 14
Independent Claim
176 words
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), and with a solution of a salt of at least one metal selected from the group consisting of Li, Mg, Mn, Zn, Cu, Ni, Co, Cr, Ba, Sr, Pb, Al, Si, Na, K, Sc, Ti, V, Ga, Ge, As, Rb, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hf, Ta, W, Pt, Au, Hg, Tl, Bi or a rare earth, wherein the first and second sols and the metal salt solution are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 15
Dependent Claim
28 words
A method as claimed in claim 12, wherein the gel is heated to form the ceramic material by dissociation, compound formation or polymorphic transformation of the mixed components.
Claim 16
Dependent Claim
66 words
A method as claimed in claim 12, wherein the hydrated ferric oxide sol is mixed with the second sol and with at least one metal salt solution, wherein the metal is selected from the group consisting of Li, Mg, Mn, Zn, Cu, Ni, Co, Cr, Ba, Sr and Pb in proportions to form a mixed sol having a composition corresponding to that of a ferrite ceramic.
Claim 17
Dependent Claim
15 words
A method as claimed in claim 14, wherein the second sol is hydrated titania sol.
Claim 18
Dependent Claim
16 words
A method as claimed in claim 12, wherein the mixed sol is dehydrated by spray drying.
Claim 19
Dependent Claim
117 words
A lithium ferrite ceramic made by the method of claim 12 and having the following properties: density--at least 95% grain size--0.2-50 microns spinwave linewidth--2-12 Oersted dielectric loss--1×10 -4 -3×10 -4 said ceramic having a spinel structure and having the formula Z.sub.Y Fe.sub.3-Y O.sub.4 wherein Z is Li which may be partly or completely replaced by Mg, Mn, Zn, Cu, Ni, Co, Cr, Ba, Sr or Pb; Y is 0.4 to 2.0; and wherein the system may also include Al, Si, Na, K, Sc, Ti, V, Ga, Ge, As, Rb, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hf, Ta, W, Pt, Au, Hg, Tl, Bi, or a rare earth.
Claim 20
Independent Claim
104 words
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is a hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 21
Independent Claim
104 words
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is a hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 22
Dependent Claim
28 words
A method as claimed in claim 18, wherein the gel is heated to form the ceramic material by dissociation, compound formation or polymorphic transformation of the mixed components.
Claim 23
Dependent Claim
16 words
A method as claimed in claim 18, wherein the second sol is a hydrated titania sol.
Claim 24
Dependent Claim
16 words
A method as claimed in claim 18, wherein the mixed sol is dehydrated by spray drying.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1995-02-24 | 1995-08-26 | 1996-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-24 | 1999-08-26 | 2000-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-24 | 2003-08-26 | 2004-02-25 | $7700.00 | Window Closed / Lapsed |