Process for Preparing Barium Titanate

• US 20090202425A1
• Filed: 08/01/2006
• Published: 08/13/2009
• Est. Priority Date: 08/04/2005
• Status: Active Grant

• Current Assignee: Hanwha Chemical Corporation
• Original Assignee: Hanwha Chemical Corporation
• Inventors: Jang, Young-Soo, Lim, Seong-Jae, Park, Sei-Ung, Ryu, Ju-Suk, Baik, Jin-Soo, Paik, Choong-Hoon
• Granted Patent: US 7,854,916 B2
• Time in Patent Office: Days
• US Class Current: 423/598
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2006/42 Magnetic properties
• CPC Class Codes: C04B 2235/528 Spheres
• CPC Class Codes: C04B 2235/5409 expressed by specific surface values
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/72 Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/79 Non-stoichiometric products, e.g. perovskites (ABO3) with an A/B-ratio other than 1
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: C04B 35/6265 involving reduction or oxidation
• CPC Class Codes: C04B 35/62655 Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying
• CPC Class Codes: C04B 35/62675 characterised by the treatment temperature
• CPC Class Codes: C04B 35/6268 characterised by the applied pressure or type of atmosphere, e.g. in vacuum, hydrogen or a specific oxygen pressure

Abstract

The present invention relates to a hydrothermal synthesis for preparing barium titanate powder as the essential material for a multi-layer ceramic capacitor. The object of the invention is to prepare barium titanate powder having high purity, particle size of submicron order, uniform particle distribution and excellent crys tallinity , by reacting hydrous titanic acid compound prepared via sulfuric acid process with crystalline titanium oxide and barium hydroxide, as the starting material, at a temperature between 60° C. and 300° C. under a pressure between 5 Kgf/cm2 and 50 Kgf/cm2. The process for preparing barium titanate according to the present invention provides barium titanate powder having Ba/Ti molar ratio of 1.000±0.002 and high purity by applying calcination under reductive condition to the solid product obtained from hydrous titanic acid compound prepared via sulfuric acid process with crystalline titanium oxide and barium hydroxide, as the starting substances, to convert barium sulfate, which was produced from residual sulfide in the raw material, to barium titanate.

Claims

1. A process for preparing barium titanate, which comprises the steps of

a) reacting hydrous titanic acid compound with crystalline titanium oxide and barium hydroxide, as the starting material, at a temperature between 60°

C. and 300°

C. under a pressure between 5 Kgf/cm² and 50 Kgf/cm² for a duration from 10 minutes to 10 hours;

b) drying and recovering the product; and

c) calcining the dry powder under reductive atmosphere at a temperature between 600°

C. and 1400°

C. for a duration from 10 minutes to 5 hours.

2. A process for preparing barium titanate according to claim 1, characterized in that the hydrous titanic acid is selected from metatitanic acid (TiO(OH)₂), orthotitanic acid (Ti(OH)₄), titanium hydrate (TiO₂xH₂O) or a mixture thereof.

3. A process for preparing barium titanate according to claim 1, characterized in that barium hydroxide is used in an excess amount with respect to hydrous titanic acid, provided that crystalline titanium oxide in an equivalent amount corresponding to the excess amount is incorporated at the same time to the reaction.

4. A process for preparing barium titanate according to claim 1, characterized in that the crystalline titanium oxide is anatase titanium oxide, rutile titanium oxide, brookite titanium oxide or a mixture thereof.

5. A process for preparing barium titanate according to claim 1, characterized in that the drying step employs spray drying or hot air drying for recovering the powder without loss of the solid content.

6. A process for preparing barium titanate according to claim 1, characterized in that the calcining step employs a mixed gas comprising 99.9˜

90% by weight of inert gas selected from nitrogen, argon or helium, and 0.1˜

10% by weight of hydrogen.

7. A process for preparing barium titanate according to claim 2, characterized in that the crystalline titanium oxide is anatase titanium oxide, rutile titanium oxide, brookite titanium oxide or a mixture thereof.

8. A process for preparing barium titanate according to claim 3, characterized in that the crystalline titanium oxide is anatase titanium oxide, rutile titanium oxide, brookite titanium oxide or a mixture thereof.