Process for preparing amorphous complex oxide precursors and products produced therefrom

• US 6,274,110 B1
• Filed: 03/11/1997
• Issued: 08/14/2001
• Est. Priority Date: 04/22/1994
• Status: Expired due to Fees

• Current Assignee: Daejung Chemicals & Metals Co., Ltd.
• Original Assignee: Yuen Shik Kim
• Inventors: Jo, Min Young, Kim, Yeun Shik, Kim, Geon Bae
• Primary Examiner(s): BOS, STEVEN J
• Application Number:
  US08/727,459
• Time in Patent Office: 1,617 Days
• Field of Search: 423/592, 423/263, 423/625
• US Class Current: 423/263
• CPC Class Codes: C01B 13/18 by thermal decomposition of compounds, e.g. of salts or hydroxides
• CPC Class Codes: C01B 13/185 Preparing mixtures of oxides
• CPC Class Codes: C01F 17/34 Aluminates, e.g. YAlO3 or Y3-xGdxAl5O12
• CPC Class Codes: C01P 2002/02 Amorphous compounds
• CPC Class Codes: C01P 2002/34 perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/85 by XPS, EDX or EDAX data
• CPC Class Codes: C01P 2002/88 by thermal analysis data, e.g. TGA, DTA, DSC
• CPC Class Codes: C01P 2006/40 Electric properties

Abstract

The present invention relates to complex oxides used as raw materials for fine ceramic materials, and more particularly to complex oxide precursors in the form of a fine powder which are readily converted to complex oxides with low energy and also a process for preparing the same.

Claims

1. A process for preparing amorphous complex oxide precursors comprising the steps of:

mixing at least one hydrated metal nitrate solution, wherein the metal is selected from the group consisting of aluminum and rare earth elements, with carbohydrazide to produce a mixture;

heating the mixture in the presence of water in a controlled manner without ignition to a temperature that is sufficient to form a homogeneous melt; and

further heating in a controlled manner without ignition at a heating rate of 1 to 100°

C. per minute to decompose the melt and to form an amorphous complex oxide precursor.

2. A process for preparing complex oxide precursors as claimed in claim 1 wherein mol-ratio of metal to carbohydrazide is equal to or more than 1.

3. A process for preparing complex oxide precursors as claimed in claim 1, wherein the mixture further comprises metal chloride.

4. A process for preparing amorphous complex oxide precursors as claimed in claim 1, wherein the metal is selected from the group consisting of yttrium and aluminum.

5. A process for preparing crystalline complex oxides comprising the steps of:

mixing at least one hydrated metal nitrate solution, wherein the metal is selected from the group consisting of aluminum and rare earth elements, with carbohydrazide to produce a mixture;

heating the mixture in the presence of water within a temperature range from a first temperature sufficient to form a homogeneous melt at a heating rate of 1 to 100°

C. per minute without ignition to produce an amorphous complex oxide precursor; and

further heating the complex oxide precursor to a crystallizing temperature to form a crystalline complex oxide.

6. A process for preparing crystalline complex oxides as claimed in claim 5 wherein the complex oxide precursor is heated up to equal to or more than 300°

C.

7. A process for preparing amorphous complex oxide precursors as claimed in claim 5, wherein the metal is selected from the group consisting of yttrium and aluminum.

8. A process for preparing amorphous complex oxide precursors comprising the steps of:

mixing at least one hydrated metal nitrate solution, wherein the metal is selected from the group consisting of aluminum and rare earth elements, with carbohydrazide to produce a mixture; and

heating the mixture in the presence of water without causing it to ignite within a temperature range defined by a first temperature sufficient to form a homogeneous melt and a second temperature at a heating rate of 1 to 100°

C. per minute to decompose the melt and to form an amorphous complex oxide precursor.

9. A process for preparing amorphous complex oxide precursors as claimed in claim 8, wherein the metal is selected from the group consisting of yttrium and aluminum.