Method for producing transparent ceramic, transparent ceramic, magneto-optical device and rare earth oxide powder for sintering

• US 10,642,073 B2
• Filed: 06/01/2015
• Issued: 05/05/2020
• Est. Priority Date: 06/04/2014
• Status: Active Grant

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Makikawa, Shinji, Aoki, Shinji, Nojima, Yoshihiro
• Primary Examiner(s): Peets, Monique R
• Application Number:
  US15/313,885
• Publication Number:
  US 20170205643A1
• Time in Patent Office: 1,800 Days
• Field of Search: 2523014, 359796
• CPC Class Codes: C01F 17/00 Compounds of rare earth metals
• CPC Class Codes: C01F 17/224 Oxides or hydroxides of lanthanides
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/60 Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
• CPC Class Codes: C04B 2235/9653 Translucent or transparent ceramics other than alumina
• CPC Class Codes: C04B 35/50 based on rare-earth compounds non-oxide rare earth compounds C04B35/5156
• CPC Class Codes: C04B 35/505 based on yttrium oxide
• CPC Class Codes: C04B 35/6264 Mixing media, e.g. organic solvents
• CPC Class Codes: C04B 35/6303 Inorganic additives
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: C04B 35/645 Pressure sintering
• CPC Class Codes: G02B 27/28 for polarising used in stereoscopes G02B30/25
• CPC Class Codes: G02F 1/0036 Magneto-optical materials
• CPC Class Codes: G02F 1/09 based on magneto-optical elements, e.g. exhibiting Faraday effect
• CPC Class Codes: G02F 1/093 used as non-reciprocal devices, e.g. optical isolators, circulators G02F1/0955 takes precedence

Abstract

A starting material powder, which contains a rare earth oxide that is composed of terbium oxide and at least one other rare earth oxide selected from among yttrium oxide, scandium oxide and oxides of lanthanide rare earth elements (excluding terbium) and a sintering assistant that is formed of an oxide of at least one element selected from among group 2 elements and group 4 elements, is produced by having (a) terbium ions, (b) ions of at least one other rare earth element selected from among yttrium ions, scandium ions and lanthanide rare earth ions (excluding terbium ions) and (c) ions of at least one element selected from among group 2 elements and group 4 elements coprecipitate in an aqueous solution containing the components (a)-(c), then filtering and separating the coprecipitate, and subjecting the separated coprecipitate to thermal dehydration.

Claims

1. A method for producing a transparent ceramic containing terbium oxide of the chemical formula:

Tb₂O₃ and at least one other rare earth oxide selected from among yttrium oxide, scandium oxide and oxides of lanthanide rare earth elements, excluding terbium, as main components, the method comprising;

providing an aqueous solution containing (a) terbium ions, (b) ions of at least one other rare earth element selected from among yttrium ions, scandium ions and lanthanide rare earth ions, excluding terbium ions, and (c) ions of at least one element selected from among Group 2 elements and Group 4 elements;

co-precipitating the components (a), (b) and (c), thereby obtaining a co-precipitate;

filtrating and separating the co-precipitate;

thermally dehydrating the co-precipitate to form a raw material powder containing a rare earth oxide including terbium oxide and at least one other rare earth oxide selected from among yttrium oxide, scandium oxide and oxides of lanthanide rare earth elements, excluding terbium, the molar ratio of terbium oxide being at least 40 mol % and the balance being the other rare earth oxide, and a sintering aid including an oxide of at least one element selected from among Group 2 elements and Group 4 elements;

forming a molded body using the raw material powder;

then firing the molded body; and

subjecting the fired molded body to pressure firing.

2. The method for producing a transparent ceramic of claim 1, wherein the raw material powder contains more than 0.5 parts by weight and up to 5 parts by weight of the sintering aid per 100 parts by weight of the rare earth oxide.

3. The method for producing a transparent ceramic of claim 1, wherein the component (c) is ions of at least one element selected from among titanium ions, zirconium ions, hafnium ions, calcium ions and magnesium ions.

4. The method for producing a transparent ceramic of claim 1, further comprising subjecting the pressure-fired molded body to a heat treatment at 1,500 to 2,000°

C. in a non-oxidizing atmosphere.

5. The method for producing a transparent ceramic of claim 1, wherein the molded body is calcined before the firing.

6. The method for producing a transparent ceramic of claim 1, wherein the co-precipitating step is a treatment of:

adding a basic aqueous solution dropwise to an acidic aqueous solution containing the ions of the components (a), (b) and (c) to produce a hydroxide;

then adding a salt containing carbonic acid ions dropwise to the hydroxide-containing solution to replace the hydroxide by a carbonate;

aging the carbonate-containing solution; and

thereafter adding a basic aqueous solution dropwise to the aged carbonate-containing solution to re-replace the carbonate by the hydroxide.

7. The method for producing a transparent ceramic of claim 6, wherein the acidic aqueous solution is aqueous nitric acid solution, aqueous sulfuric acid solution or aqueous hydrochloric acid solution.

8. The method for producing a transparent ceramic of claim 6, wherein the basic aqueous solution is aqueous ammonia (NH₄OH), oxalic acid ((COOH)₂), ammonium hydrogen carbonate (NH₄HCO₃), or ammonium carbonate ((NH₄)₂CO₃).

9. The method for producing a transparent ceramic of claim 1, wherein in the transparent ceramic, an insertion loss at a wavelength of 1,064 nm inclusive of a reflection loss at an end face in a plane of at least 90% of a measurement surface in a thickness direction of a 10 mm-thick sample is up to 0.97 dB.