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US 5,242,674 AGranted
Process for preparing crystalline mixed metal oxides
AssigneeE. I. Du Pont de Nemours and Company
InventorsSalvatore A. Bruno, William L. Monson
Life of this patent
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Abstract
An improved process for preparing crystalline mixed metal oxides, such as barium titanate, in which an organometallic compound is reacted simultaneously and continuously with a solution of a divalent metal ion in an alkaline high turbulence energy environment, the reaction product is crystallized, and the crystals are isolated and may be calcined.
Claims16
A process for preparing crystalline mixed metal oxides having an A/B ratio of from about 0.990 to about 1.029 of the formula:
- ABO.sub.3
- wherein,
- A is a metal cation selected from Ba, Sr, Ca, Mg, Pb and Nd and mixtures thereof;
- and
- B is a metal cation selected from Ti, Zr, Nb, Hf, Zn and Sn and mixtures thereof which comprises the steps of:
- (a) simultaneously and continuously mixing an organometallic compound, or mixture of organometallic compounds or a hydrolyzable system, of the structure BL.sub.n, where B is as defined above, L is a hydrolyzable group, or a combination of such groups, selected from the group consisting of an alkoxy, aryloxy, aminoalkyl, acetoxy, acetoacetonyl, a chloride, a nitrate and an acetate and n is 2 or 4 with a solution of a compound, or a mixture of compounds, of the general structure AXy, where A is as defined above, X is an anion, or combination of anions, selected from the group consisting of hydroxide, chloride, nitrate and acetate, and y is 2 or 3 in an alkaline, high turbulence energy environment of a coaxial jet mixer;
- wherein said environment is characterized by a turbulence intensity of greater than about 14.times.10.sup.6 cm/sec.sup.3 ;
- (b) crystallizing a reaction product;
- and
- (c) recovering the crystals, wherein 90% of the particles have a particle size between 0.2 and 1.0 micron and have a surface area of less than about 50 m.sup.2 /g.
7 more elements
A process for preparing crystalline barium titanate which comprises the steps of:
- (a) reacting tetrabutyl titanate as a first ingredient stream with a solution of barium hydroxide as a second ingredient stream at a temperature of 80.degree.-85.degree. C. in a high turbulence energy environment comprising pumping said ingredient streams simultaneously and continuously through a coaxial jet mixer, said environment characterized by a turbulence intensity greater than about 14.times.10.sup.6 cm/sec.sup.3 to form a slurry and discharging said slurry into an alkaline heel of water;
- (b) crystallizing said slurry by heating under reflux with continuous agitation for at least about 6 hours to no more than 48 hours;
- and
- (c) recovering crystalline barium titanate having 90% of the particles greater than 0.2 um in size up to about 1.0 .mu.m in size, and a surface area of less than about 50 m.sup.2 /g.
1 more element
A chemically homogeneous crystalline mixed metal oxide having an A/B ratio in the range of about 0.990 to about 1.029 of the formula:
- ABO.sub.3
- wherein,
- A is a metal cation selected from Ba, Sr, Ca, Mg, Pb, Nd and mixtures thereof;
- and
- B is a metal cation selected from Ti, Zr, Nb, Hf, Zn, Sn and mixtures thereof which comprises the steps of:
- (a) simultaneously and continuously mixing an organometallic compound, or mixture of organometallic compounds, of the general structure BL.sub.n where B is as defined above, L is a hydrolyzable group, or combination of such groups, selected from the group consisting of an alkoxy, aryloxy, aminoalkyl, acetoxy, and acetoacetonyl, and n is 2, 4, or 5 as a first ingredient stream with a solution of a compound, or a mixture of compounds, of the general structure AXy, where A is as defined above, X is an anion, or a combination of anions, selected from the group consisting of a hydroxide, chloride, nitrate and an acetate, and y is 2 or 3 in an alkaline, high turbulence energy environment comprising pumping said ingredient streams simultaneously and continuously through a coaxial jet mixer which produces a turbulence intensity greater than about 14.times.10.sup.6 cm/sec.sup.3 ;
- (b) crystallizing a reaction product for at least 6 hours to no more than 48 hours;
- and
- (c) recovering the crystals, wherein 90% of the crystalline mixed metal oxide is greater than 0.2 .mu.m in size up to about 1.0 .mu.m in size, and a surface area of less than about 50 m.sup.2 /g.
6 more elements
Dependencies are inferred from the claim text.