Alumina sintered body and base substrate for optical device

Patent metadata

Field	Value
Publication number	US-10138166-B2
Application number	US-201715447670-A
Country	US
Kind code	B2
Filing date	Mar 2, 2017
Priority date	Nov 28, 2014
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

An alumina sintered body according to the present invention has a degree of c-plane orientation of 90% or more as determined by Lotgering's method from an X-ray diffraction profile obtained by irradiating a plate surface with X-rays in a range of 2θ=20° to 70°. The alumina sintered body has no pores when a cross-sectional surface formed in a direction perpendicular to the plate surface is polished using an Ar+ ion beam and a mask and is examined under a scanning electron microscope at a magnification of 5,000 times. The alumina sintered body has a total mass fraction of impurity elements other than Mg and C of 100 ppm or less. This alumina sintered body has a high degree of orientation, high density, and high purity and thus has a higher optical translucency than those known in the art.

First claim

What is claimed is:

1. An alumina sintered body having a surface with a degree of c-plane orientation of 90% or more as determined by Lotgering's method from an X-ray diffraction profile obtained by X-ray irradiation in a range of 2θ=20° to 70°,
having no pores when any cross-sectional surface is polished by ion milling and is examined under a scanning electron microscope at a magnification of 5,000 times,
having a total mass fraction of impurity elements other than Mg and C of 100 ppm or less, and
wherein the alumina sintered body contains 30 to 70 ppm by mass fraction of C.

2. The alumina sintered body according to claim 1 , wherein a 0.2 mm thick specimen removed from the alumina sintered body has an in-line transmittance of 70% or more at wavelengths of 350 to 1,000 nm.

3. The alumina sintered body according to claim 1 , containing 125 ppm or less by mass fraction of Mg.

4. The alumina sintered body according to claim 3 , wherein a value obtained by subtracting the minimum in-line transmittance at wavelengths of 350 to 1,000 nm of a 0.2 mm thick specimen removed from the alumina sintered body after immersion in a Na flux at 870° C. under nitrogen for 120 hours from the minimum in-line transmittance at wavelengths of 350 to 1,000 nm of the 0.2 mm thick specimen removed from the alumina sintered body before the immersion in the Na flux is 5% or less.

5. A base substrate for an optical device, comprising the alumina sintered body according to claim 1 .

6. A base substrate for an optical device, comprising the alumina sintered body according to claim 4 .

Assignees

• Ngk Insulators Ltd

Inventors

• Matsushima Kiyoshi
• Watanabe Morimichi
• Sato Kei
• Nanataki Tsutomu

Classifications

• C30B28/02

  directly from the solid state · CPC title

• C30B1/12

  by pressure treatment during the growth · CPC title

• C30B1/04

  Isothermal recrystallisation · CPC title

• C04B35/6455

  Hot isostatic pressing · CPC title

• C04B2235/77

  Density · CPC title