Barium titanate particles with surface deposition of rare earth element
First Claim
1. Composite particles of barium titanate bearing a water-insoluble compound of a rare earth element deposited on the surface of the particle, in which each particle has a cladding/core structure consisting of a core particle of barium titanate and a cladding layer of a water-insoluble salt or oxide of a rare earth element uniformly deposited on the core particle.
1 Assignment
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Accused Products
Abstract
Disclosed is a powder consisting of composite barium titanate particles having surface deposition of a water-insoluble rare earth compound such as yttrium oxide. The powder is used advantageously as a base material for the preparation of a sintered body such as ceramic capacitors of small thickness or compact size as compared with conventional powder blends of barium titanate particles and yttrium oxide particles in respect of greatly improved uniformity in the distribution of the yttrium element. The composite barium titanate particles with surface deposition of yttrium oxide can be prepared by conducting hydrolysis of urea in an aqueous medium containing a water-soluble yttrium salt dissolved therein in the presence of barium titanate particles to deposit basic yttrium carbonate on the particle surface followed by calcination of the particles to convert the basic yttrium carbonate into yttrium oxide.
33 Citations
13 Claims
- 1. Composite particles of barium titanate bearing a water-insoluble compound of a rare earth element deposited on the surface of the particle, in which each particle has a cladding/core structure consisting of a core particle of barium titanate and a cladding layer of a water-insoluble salt or oxide of a rare earth element uniformly deposited on the core particle.
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6. A method for the preparation of composite particles of barium titanate bearing a basic carbonate of a rare earth element deposited on the surface of the particles which comprises the steps of:
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(a) dispersing particles of barium titanate in an aqueous solution as a suspension medium containing a water-soluble salt of the rare earth element and urea to form an aqueous suspension of the particles of barium titanate;
(b) heating the aqueous suspension of the particles of barium titanate at a temperature of 70°
C. or higher to deposit a basic carbonate of the rare earth element on the surface of the particles of barium titanate; and
(c) separating the particles of barium titanate bearing a basic carbonate of the rare earth element deposited on the surface from the suspension medium. - View Dependent Claims (7, 8, 9, 10)
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11. A method for the preparation of composite particles of barium titanate bearing an oxide of a rare earth element deposited on the surface of the particles which comprises the steps of:
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(a) dispersing particles of barium titanate in an aqueous solution as a suspension medium containing a water-soluble salt of the rare earth element and urea to form an aqueous suspension of the particles of barium titanate;
(b) heating the aqueous suspension of the particles of barium titanate at a temperature of 70°
C. or higher to deposit a basic carbonate of the rare earth element on the surface of the particles of barium titanate;
(c) separating the particles of barium titanate bearing a basic carbonate of the rare earth element deposited on the surface from the suspension medium; and
(d) calcining the particles of barium titanate bearing a basic carbonate of the rare earth element deposited on the surface at a temperature of 600°
C. or higher in an atmosphere of an oxidizing gas.- View Dependent Claims (12)
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13. A method for the preparation of composite particles of barium titanate bearing an oxide of a rare earth element deposited on the surface of the particles which comprises the steps of:
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(a) dispersing particles of barium titanate in an aqueous solution as a suspension medium containing a water-soluble salt of the rare earth element to form an aqueous suspension of the particles of barium titanate;
(b) admixing the aqueous suspension of the particles of barium titanate with ammonia or ammonia water to deposit a hydroxide of the rare earth element on the surface of the barium titanate particles;
(c) separating the particles of barium titanate bearing a hydroxide of the rare earth element deposited on the surface from the suspension medium; and
(d) calcining the particles of barium titanate bearing a hydroxide of the rare earth element deposited on the surface at a temperature of 600°
C. or higher.
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Specification