# US 2014/0193743 A1 · Method for the densification of ceramic layers, especially ceramic layers within solid oxide cell (soc) technology, and products obtained by the method

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- Number: US 2014/0193743 A1
- Document ID: US20140193743A1
- Status: Published application
- Kind: A1
- Application number: 14/233,721
- Filed: 2012-07-20
- Published: 2014-07-10
- Earliest claimed: 2011-07-22
- Assignees: Danmarks Tekniske Universitet
- Inventors: Vincenzo Esposito
- Web page: https://patentgrep.com/patent/US20140193743A1

## CPC

- C04B 41/4582: {Porous coatings, e.g. coating containing porous fillers}
- C04B 41/0072: {Heat treatment}
- C04B 41/009: {characterised by the material treated}
- C04B 41/52: Multiple coating or impregnating {multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation}
- C04B 41/5353: {Wet etching, e.g. with etchants dissolved in organic solvents}
- C04B 41/89: for obtaining at least two superposed coatings having different compositions
- C04B 41/91: involving the removal of part of the materials of the treated articles, e.g. etching
- C25B 9/17: Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- H01M 8/0245: in the form of layered or coated products
- H01M 8/1246: the electrolyte consisting of oxides
- H01M 8/126: the electrolyte containing cerium oxide
- H10N 30/853: Ceramic compositions
- C04B 2111/00853: {in electrochemical cells or batteries, e.g. fuel cells}
- H01M 2300/0074: Ion conductive at high temperature
- H01M 2300/0094: in the form of layered products, e.g. coatings
- Y02E 60/50: Fuel cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- Y10T 428/24997: Of metal-containing material
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B)
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A ceramic layer, especially for use in solid oxide cell (SOC) technology, is densified in a method comprising (a) providing a multilayer system by depositing the porous ceramic layer, which is to be densified, onto the selected system of ceramic layers on a support, (b) pre-sintering the resulting multilayer system at a temperature T1 to consolidate a sintered, but porous layer, (c) impregnating a solution or suspension of one or more sintering aids directly into the layer to be densified, (d) evaporating the solution or suspension of step (c) to obtain a homogeneous dispersion of the sintering aid(s) in the porous layer surface and (e) performing a thermal treatment at a temperature T2, where T2>T1, to obtain densification of and grain growth in the porous layer formed in step (b). The method makes it possible to obtain dense ceramic layers at temperatures, which are compatible with the other materials present in a ceramic multilayer system.

## Claims

### Claim 1

A method for the densification of porous ceramic layers by an in-situ solid state reaction, said method comprising:
(a) providing a multilayer system by depositing the porous ceramic layer, which is to be densified, onto the selected system of ceramic layers on a support,
(b) pre-sintering the resulting multilayer system by applying a temperature T1 to said multilayer system thereby consolidating and pre-sintering, said porous ceramic layer,
(c) impregnating a solution or suspension of one or more sintering aids directly into said porous ceramic layer to be densified,
(d) evaporating the solution or suspension of step (c) to obtain a homogeneous dispersion of the sintering aid(s) in said porous ceramic layer and
(e) performing a thermal treatment by applying a temperature T2 to said multilayer system, where T2>T1, thereby obtaining densification of and grain growth in said porous layer formed in step (b) and thus providing a densified porous ceramic layer having a structure where a grain size (g) and thickness (t) of the densified porous ceramic layer stand in relation to one another as given by
g/t>0.1.

### Claim 2 (depends on 1)

Method according to claim 1, wherein the porous ceramic layer to be densified consists of gadolinium-doped cerium oxide (CGO).

### Claim 3 (depends on 2)

Method according to claim 2, wherein T1 is in the 850-1350° C. range and T2>T1.

### Claim 4 (depends on 1)

Method according to claim 1, wherein said one or more sintering aids are selected from the group consisting of Co, Fe, Cr, Mn, Ni, Zn, Cu, Bi, Li, K, Ca or Ba salts and/or oxides and their mixtures.

### Claim 5 (depends on 1)

Method according to claim 1, wherein the deposition in step (a) is done by casting, multi casting and lamination at the green stage, by screen printing, by spraying techniques, by physical vapour deposition (PVD) or by chemical vapour deposition (CVD).

### Claim 6 (depends on 4)

Method according to claim 4, wherein said one or more sintering aids are selected from cobalt oxides and cobalt salts.

### Claim 7 (depends on 1)

A method according to claim 1, said method further comprising:
(f) a selected chemical etching to remove traces of said one or more sintering aids thereby cleaning said densified porous ceramic layer.

### Claim 8 (depends on 1)

Use of a multilayer system with a densified ceramic layer produced by a method according to claim 1, within solid oxide cell (SOC) technology.

### Claim 9 (depends on 1)

Use of a multilayer system with a densified ceramic layer produced by a method according to claim 1, within piezo-electric technology.

### Claim 10

A multilayer system, comprising:
a selected system of ceramic layers on a support
at least one densified porous ceramic layer, located on top of said selected system of ceramic layers,
wherein said at least one densified porous ceramic layer has a structure where a grain size (g) and thickness (t) of said at least one densified porous ceramic layer stand in relation to one another as given by
g/t>0.1.

### Claim 11 (depends on 10)

A multilayer system, according to claim 10, wherein said at least one densified porous ceramic layer shows evidences of discontinuous or abnormal grain growth.

### Claim 12 (depends on 10)

A multilayer system, according to claim 10, wherein said at least one densified porous ceramic layer has a monodisperse porosity in the submicron range, oriented in the same direction of the stress forces induced by constrained sintering, interconnected or localized at the grain boundary and at the triple point, thereby generated in constrained sintering conditions.

### Claim 13 (depends on 10)

A multilayer system, according to claim 10, wherein said at least one layer of said selected system of ceramic layers has polydisperse porosity.

### Claim 14 (depends on 10)

A multilayer system, according to claim 10, wherein said at least one densified porous ceramic layer comprises one or more sintering aids.

### Claim 15 (depends on 14)

A multilayer system, according to claim 14, wherein said at least one densified porous ceramic layer comprises one or more sintering aids embedded into one or more grains of said at least one densified porous ceramic layer.

### Claim 16 (depends on 14)

A multilayer system, according to claim 14, wherein said one or more sintering aids are present in a concentration between 1 and 30% vol within 1 μm below the top surface of said at least one densified porous ceramic layer.

### Claim 17 (depends on 14)

A multilayer system, according to claim 14, wherein said one or more sintering aids are present in a concentration higher than 5% vol within 1 μm below the top surface of said at least one densified porous ceramic layer.

### Claim 18 (depends on 10)

A multilayer system, according to claim 10, wherein the relative density at the interface between said at least one densified porous ceramic layer and said selected system of ceramic layers is higher than 80% vol.