Alumina sintered body and base substrate for optical device

• US 10,138,166 B2
• Filed: 03/02/2017
• Issued: 11/27/2018
• Est. Priority Date: 11/28/2014
• Status: Active Grant

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Matsushima, Kiyoshi, Watanabe, Morimichi, Sato, Kei, Nanataki, Tsutomu
• Primary Examiner(s): Fiorito, James A
• Application Number:
  US15/447,670
• Publication Number:
  US 20170174574A1
• Time in Patent Office: 635 Days
• CPC Class Codes: C01F 7/02 Aluminium oxide; Aluminium hydroxide; Aluminates
• CPC Class Codes: C01F 7/30 Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
• CPC Class Codes: C01F 7/441 by calcination
• CPC Class Codes: C01F 7/442 in presence of a calcination additive
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/20 extending in two dimensions, e.g. plate-like
• CPC Class Codes: C01P 2004/54 Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2006/80 Compositional purity
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/322 Transition aluminas, e.g. delta or gamma aluminas
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
• CPC Class Codes: C04B 2235/425 Graphite
• CPC Class Codes: C04B 2235/445 Fluoride containing anions, e.g. fluosilicate
• CPC Class Codes: C04B 2235/5292 Flakes, platelets or plates
• CPC Class Codes: C04B 2235/5296 with a defined aspect ratio, e.g. indicating sphericity
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/6025 : Tape casting, e.g. with a doctor blade
• CPC Class Codes: C04B 2235/604 : Pressing at temperatures other than sintering temperatures
• CPC Class Codes: C04B 2235/612 : Machining
• CPC Class Codes: C04B 2235/656 : characterised by specific heating conditions during heat treatment
• CPC Class Codes: C04B 2235/6567 : Treatment time
• 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 2235/721 : Carbon content
• CPC Class Codes: C04B 2235/725 : Metal content
• CPC Class Codes: C04B 2235/77 : Density
• CPC Class Codes: C04B 2235/787 : Oriented grains
• CPC Class Codes: C04B 2235/9653 : Translucent or transparent ceramics other than alumina
• CPC Class Codes: C04B 2235/9692 : Acid, alkali or halogen resistance
• CPC Class Codes: C04B 35/115 : Translucent or transparent products
• 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
• CPC Class Codes: C04B 35/6303 : Inorganic additives
• CPC Class Codes: C04B 35/632 : Organic additives
• CPC Class Codes: C04B 35/6342 : Polyvinylacetals, e.g. polyvinylbutyral [PVB]
• CPC Class Codes: C04B 35/638 : Removal thereof
• CPC Class Codes: C04B 35/645 : Pressure sintering
• CPC Class Codes: C04B 35/6455 : Hot isostatic pressing
• CPC Class Codes: C30B 1/04 : Isothermal recrystallisation
• CPC Class Codes: C30B 1/10 : by solid state reactions or multi-phase diffusion
• CPC Class Codes: C30B 1/12 : by pressure treatment during the growth
• CPC Class Codes: C30B 28/02 : directly from the solid state
• CPC Class Codes: C30B 29/20 : Aluminium oxides
• CPC Class Codes: G02B 1/00 : Optical elements characterised by the material of which they are made; Optical coatings for optical elements
• CPC Class Codes: H01L 33/0093 : Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/28 : containing only elements of Group II and Group VI of the Periodic Table
• CPC Class Codes: H01L 33/32 : containing nitrogen

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.

Claims

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.