|Title of Invention||
PEROVSKITE CERAMIC MATERIAL
|Abstract||Perovskite ceramic material having the general formula: Ax A'x' A"x" By B'y' B"y" 03-0' wherein A, A' and A" each is one or more metals selected from the group of lanthanide metalsi B, B' and B" each is a metal selected from the group of transition metals and group 3a, and noble metals of group 8bi x + x' + x" < 1 and/ or y + y' + y" < 1 such that EXi ~ EYio|
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a ceramic material in particular to parasite type ceramic for use in the manufacturer of ion and/or electron conducting ceramic prod- '
Description of the Related Art
Parasite ceramic materials for use in oxygen separation
membranes, having the general formula:
are known from US Patent No. 5,240,473.: The ceramic materials of the above US Patent have a stoichiometric perovskite composition, wherein Ex’ and Ey’ are 1.
It has been found by the present inventors that non-stoichiometric perovskite type ceramic materials,; wherein Lx and/or Ly are less than 1, show an improved stability and reduced reactivity with metals or metal oxides supported on or otherwise combined the ceramic material.
Furthermore, it has been proved by the present inventors that A-site deficit induce an increased electronic and ionic conductivity due to an increase defect concentration in the material.
SUMMARY OF THE INVENTION
Pursuant to the unexpected finding noted above, the* present invention provides a perovskite ceramic material having the general formula:
B, B' and B" each is a metal selected from the group of transition metals, group 3a, and noble metals of group 8b;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In a specific embodiment of the invention, the material has a composition with the formula:
Ln is a combination of Ce, Pr and Dn and optional further lanthanide metal;
M is at least one alkaline earth metal; M' is at least one metal selected from Group 2a/ 3b, 4b, 5b, 6b, 7b, 8, lb, 2b, 3a, 4a and noble metals of group 8b metals of the periodic table; and
Using drip pyrolysis procedure a ceramic powder was produced. Aqueous solutions of metal nitrates, acetates or carbonates were mixed in the required proportions according to the proposed chemical formula. Then combustion fuel such as glucose or glycine was added to the above solutions in order to get fuel-rich mixtures. The as prepared stock solutions were drip pyrolyzed into a rotary kiln. The resulting powders were characterized by using XRD,' SEM, BET and the particle size distribution was determined using a laser light scattering technique.
The powders were found to have a perovskite structure.
This material of Example 1 may be used such as SOFC cathode material, oxidation catalyst and sensor and the proposed chemical formula is:
The powder XRD lines for this compound are presented in Table 1.
: ' '
Another material, which may be used for application such
as: SOFC cathode, mixed electronic/ionic conductive Mem
brine, oxidation catalyst and sensor, has been synthesized
as mentioned in Example 1. The material; has the chemical
This A-site deficient perovskite compound was proved to have better chemical stability towards Yttria-Stabilized Zirconia compared to that with A/B = 1. Also, this compound showed high electronic conductivity (120 S/cm at 850*’C in air). The crystalline structure is rhombohedral with parameters (in hexagonal setting): a’ = 5.520 A, c’ = 13.510 A.
An another material which may be used for SOFC interconnection, and electronic ceramic compounds such as sensor and heating element in Magneto-Hydro-Dynamic (MHD) devices is:
The as synthesized material (after the procedure mentioned in Example 1) showed a perovskite structure according to ■ Table 2.
Pellets were cold pressed and sintered' at 1600°Ci. The electric conductivity, at 1000° C, was dependent of environmental atmosphere as follows:
50.5 S/cm(Po2 = 0,21 atm)26.0 S/cm(Po2 = 10"'‘‘ atm)6.4 S/cm (Po2=5-10'‘‘ atm).
Another material for SOFC electrolyte, oxygen ion membrane and catalyst is synthesized according to Example 1. The chemical formula in this Example is:
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.
1. Perovskite ceramic material having the general
A, A' and A" each is one or more metals selected from the
group of lanthanide metals; '
B, B' and B" each is a metal selected from the group of
transition metals and group 3a, and noble metals; of group
2. The ceramic material of claim 1, having the formula
Laa Lnb Mc Gad M'e 03-5, wherein Ln is a combination of Ce,
Pr and Nd and optionally a further lanthanide metal;
M is at least one alkaline earth metal;
M' is at least one metal selected from Group 2a, 3b, 4b,
5b, 6b, 7b, 8, lb, 2b, 3a, 4a and noble metals of group 8b
metals of the periodic table; and
6. The ceramic material of claim 1, having the formula
7. Use of the ceramic material of any one of the
preceding claims for the manufacture of ion and/or electron
8. Perovskite ceramic material, substantially as hereinabove described and exemplified.
|Indian Patent Application Number||310/MAS/1999|
|PG Journal Number||50/2007|
|Date of Filing||17-Mar-1999|
|Name of Patentee||M/S. HALDOR TOPSOE A/S|
|Applicant Address||NYMOLLEVEJ 55,DK-2800 LYNGBY|
|PCT International Classification Number||C04B35/50|
|PCT International Application Number||N/A|
|PCT International Filing date|