Method for manufacturing alumina sintered body and alumina sintered body

Patent metadata

Field	Value
Publication number	US-9630380-B2
Application number	US-201615079557-A
Country	US
Kind code	B2
Filing date	Mar 24, 2016
Priority date	Mar 26, 2015
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A method for manufacturing an alumina sintered body, according to the present invention, includes the steps of (a) obtaining a compact by putting a slurry containing an Al 2 O 3 powder, a MgO powder, a MgF 2 powder, a solvent, a dispersing agent, and a gelatinizer into a mold, gelatinizing the slurry by a chemical reaction of the gelatinizer in the mold, and causing mold release, (b) obtaining a calcined body by drying the compact, performing degreasing, and further performing calcination, and (c) obtaining a ceramic sintered body by subjecting the calcined body to hot-press firing at 1,150° C. to 1,350° C. In the step (a), the Al 2 O 3 powder having a purity of 99.9 percent by mass or more is used and 0.1 to 0.2 parts by mass of MgO powder and 0.13 parts by mass or less of MgF 2 powder relative to 100 parts by mass of Al 2 O 3 powder are used.

First claim

What is claimed is:

1. An alumina sintered body, containing 0.09 to 0.17 percent by mass of Mg element and 0.03 to 0.04 percent by mass of F element, and having a volume resistivity at 400° C. of 1.0×10 15 Ω·cm or more, a withstand voltage of 130 kV/m or more, an average grain size of 0.5 to 10 μm, and 3σ of the grain size of 1 to 20 μm, σ representing a standard deviation.

2. The alumina sintered body according to claim 1 , having the average grain size of 1 to 2 μm and the 3σ of the grain size of 1 to 2 μm.

3. A method for manufacturing the alumina sintered body according to claim 1 , comprising the steps of:
(a) obtaining a compact by putting a slurry containing an Al 2 O 3 powder, a MgO powder, a MgF 2 powder, a solvent, a dispersing agent, and a gelatinizer into a mold, gelatinizing the slurry by a chemical reaction of the gelatinizer in the mold, and causing mold release;
(b) obtaining a calcined body by drying the compact, performing degreasing, and further performing calcination; and
(c) obtaining a ceramic sintered body by subjecting the calcined body to hot-press firing at 1,150° C. to 1,350° C.,
wherein in the step (a), the Al 2 O 3 powder having a purity of 99.9 percent by mass or more is used and 0.1 to 0.2 parts by mass of the MgO powder and 0.13 parts by mass or less of the MgF 2 powder relative to 100 parts by mass of the Al 2 O 3 powder are used in preparation of the slurry.

4. The method for manufacturing an alumina sintered body according to claim 3 ,
wherein in the step (a), 0.09 to 0.13 parts by mass of the MgF 2 powder relative to 100 parts by mass of the Al 2 O 3 powder are used in preparation of the slurry.

Assignees

• Ngk Insulators Ltd

Inventors

• Nobori Kazuhiro
• Kimura Takuji

Classifications

• C04B2237/343

  Alumina or aluminates · CPC title

• C04B2235/786

  Micrometer sized grains, i.e. from 1 to 100 micron · CPC title

• C04B2235/784

  Monomodal · CPC title

• C04B2235/77

  Density · CPC title

• C04B2235/6023

  Gel casting · CPC title