Patent EP0338799A2 successfully refreshed from Google Patents.
EP0338799A2
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Sol-gel method of making ceramics
Assignee: Rio Tinto Alcan International Ltd
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Filing: 1989-04-19
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Granted: —
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Expires: 2009-04-19
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 Louis Woodhead
- 👤 Paul Groves
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 13:46
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: 13
Claim 1
Independent Claim
83 words
A method of making a ceramic material, selected from a titanate ceramic having a perovskite-type structure and a ferrite ceramic having a spinel-type structure, which method comprises mixing a first hydrated oxide sol with at least one second sol and/or at least one metal salt solution in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 2
Independent Claim
83 words
A method of making a ceramic material, selected from a titanate ceramic having a perovskite-type structure and a ferrite ceramic having a spinel-type structure, which method comprises mixing a first hydrated oxide sol with at least one second sol and/or at least one metal salt solution in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Claim 3
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 4
Dependent Claim
46 words
A method as claimed in claim 1 or claim 2, 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-type ceramic.
Claim 5
Dependent Claim
41 words
A method as claimed in claim 3, 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 6
Dependent Claim
59 words
A method as claimed in claim 1 or claim 2, wherein a hydrated ferric oxide sol is mixed with at least one metal salt solution, wherein the metal is selected from 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 7
Dependent Claim
17 words
A method as claimed in claim 5, wherein a hydrated titania sol is included in the mixture.
Claim 8
Independent Claim
21 words
A method as claimed in any one of claims 1 to 6, wherein the mixed sol is dehydrated by spray drying.
Claim 9
Independent Claim
29 words
A method as claimed in any one of claims 1 to 7, wherein the gel is heated at a temperature of 250°C to 650°C to form the ceramic material.
Claim 10
Independent Claim
20 words
A method as claimed in any one of claims 1 to 8, wherein the ceramic material is pressed and sintered.
Claim 11
Dependent Claim
43 words
A PZT4 ceramic made by the method of any one of claims 1 to 9 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
56 words
A PZT5 ceramic made by the method of any one of claims 1 to 9 and having the following properties: density - at least 95% piezoelectric coefficent - 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
Dependent Claim
50 words
A lithium ferrite ceramic made by the method of any one of claims 1 to 9 and having the following properties: density - at least 95% grain size - 0.2 - 50 microns spinwave linewidth - 2 - 12 Oersted dielectric loss - 1 x 10⁻⁴ - 3 x 10⁻⁴
References Cited (Backward Citations)
No citation records indexed.
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