TRANSPARENT CERAMIC, METHOD FOR MANUFACTURING SAME, AND MAGNETO-OPTICAL DEVICE

• US 20140002900A1
• Filed: 03/15/2012
• Published: 01/02/2014
• Est. Priority Date: 03/16/2011
• Status: Active Grant

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Makikawa, Shinji, Yahagi, Akira, Ikesue, Akio
• Granted Patent: US 9,470,915 B2
• Time in Patent Office: Days
• US Class Current: 359/484.03
• 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 2235/3224 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 2235/3232 Titanium oxides or titanates, e.g. rutile or anatase
• CPC Class Codes: C04B 2235/3244 Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3251 Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3286 Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/3287 Germanium oxides, germanates or oxide forming salts thereof, e.g. copper germanate
• 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 glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/3852 Nitrides, e.g. oxynitrides, carbonitrides, oxycarbonitrides, lithium nitride, magnesium nitride
• CPC Class Codes: C04B 2235/445 Fluoride containing anions, e.g. fluosilicate
• CPC Class Codes: C04B 2235/661 Multi-step sintering
• CPC Class Codes: C04B 2235/664 Reductive annealing
• CPC Class Codes: C04B 2235/762 Cubic symmetry, e.g. beta-SiC
• CPC Class Codes: C04B 2235/785 Submicron sized grains, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/81 Materials characterised by the absence of phases other than the main phase, i.e. single phase materials
• 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 35/62685 : characterised by the order of addition of constituents or additives
• CPC Class Codes: C04B 35/645 : Pressure sintering
• CPC Class Codes: C04B 35/6455 : Hot isostatic pressing
• CPC Class Codes: G02F 1/0036 : Magneto-optical materials
• CPC Class Codes: G02F 1/093 : used as non-reciprocal devices, e.g. optical isolators, circulators G02F1/0955 takes precedence

Abstract

A transparent ceramic having terbium oxide (Tb₂O₃) in a molar ratio of at least 40%; and at least one oxide selected among an yttrium oxide, a scandium oxide, and a lanthanide rare earth oxide, wherein (1) the crystal structure of the terbium-oxide-based ceramic does not contain a non-cubic-crystal phase, (2) the mean crystal particle diameter is in a range of 0.5 to 100 μm, and (3) the ceramic comprises a sintering auxiliary having no incidence of deposition of a non-cubic-crystal phase in the crystal structure of the terbium-oxide-based ceramic. This transparent ceramic makes a magneto-optical element that performs at least as well as terbium gallium garnet or other existing monocrystal materials. It also makes a functional element for an optical isolator in the infrared region between 500 nm and 1.5 μm having very little scattering and very few birefringence components.

Claims

1. A transparent ceramic material comprising at least 40% in molar fraction of terbium oxide (chemical formula Tb₂O₃) and at least one oxide selected from among yttrium oxide, scandium oxide, and a lanthanide rare earth oxide as main components wherein

(1) the crystal structure of the terbium oxide-based ceramic material does not contain any heterophase but cubic,

(2) the mean crystal grain size is in a range of 0.5 to 100 μ

m, and

(3) the ceramic material comprises a sintering aid which does not cause any heterophase but cubic to precipitate in the crystal structure of the terbium oxide-based ceramic material.

2. The transparent ceramic material of claim 1 wherein the sintering aid is an oxide, fluoride or nitride of an element selected from among titanium, zirconium, hafnium and calcium.

3. The transparent ceramic material of claim 1 which has (1) an in-line transmittance of at least 70% at wavelength 1,000 nm and (2) an in-line transmittance of at least 55% at wavelength 600 nm, as measured in a thickness direction of a sample of 10 mm thick.

4. The transparent ceramic material of claim 1 which has an insertion loss of up to 1.2 dB at wavelength 1,065 nm, inclusive of a reflection loss at the end face within a plane of at least 90% of the measurement surface.

5. The transparent ceramic material of claim 1 which has an extinction ratio of at least 30 dB at wavelength 1,065 nm and within a plane of at least 90% of the measurement surface.

6. The transparent ceramic material of claim 1 which has a refractive index distribution within 5×

10^{31 5} at wavelength 633 nm, as measured at a thickness of 10 mm and on the transmission wavefront in a region of at least 90% of the measurement surface.

11. A magneto-optical device constructed using the transparent ceramic material of claim 1.

12. A magneto-optical device comprising a Faraday rotator using the transparent ceramic material of claim 1.

13. The magneto-optical device of claim 12, which is used as an optical isolator comprising polarizing materials upstream and downstream of the Faraday rotator and operating in a wavelength region of wavelength 1,065 nm.

7. A method for manufacturing a transparent ceramic material, comprising:

the first step (1) of grinding and mixing source powders including (a) terbium oxide, (b) at least one oxide selected from among yttrium oxide, scandium oxide, and a lanthanide rare earth oxide, and (c) a sintering aid which does not cause any heterophase but cubic to precipitate in the crystal structure of a terbium oxide-based ceramic material, said source powders having a mean primary particle size of 30 to 2,000 nm, shaping the powder mix to form a green compact,

the second step (2) of calcining the green compact at 200 to 1,000°

C. in a non-oxidizing or oxidizing atmosphere to form a calcined body,

the third step (3) of firing the calcined body at 1,400 to 1,700°

C. in a non-oxidizing atmosphere to form a fired body, and

the fourth step (4) of pressure firing the fired body at 1,400 to 1,800°

C. under a pressure of 19 to 196 MPa to form a pressure fired body.

10. The method of claim 7, further comprising the step of annealing the pressure fired body at 1,500 to 2,000°

C. in an oxygen-free atmosphere.

8. A method for manufacturing a transparent ceramic material, comprising:

the first step (1) of grinding and mixing source powders including (a) terbium oxide, (b) at least one oxide selected from among yttrium oxide, scandium oxide, and a lanthanide rare earth oxide, and (c) a sintering aid which does not cause any heterophase but cubic to precipitate in the crystal structure of a terbium oxide-based ceramic material, said source powders having a mean primary particle size of 30 to 2,000 nm, calcining the powder mix at 200 to 1,000°

C. in a non-oxidizing or oxidizing atmosphere, and shaping the powder mix to form a compact,

the second step (2) of firing the compact at 1,400 to 1,700°

C. in a non-oxidizing atmosphere to form a fired body, and

the third step (3) of pressure firing the fired body at 1,400 to 1,800°

C. under a pressure of 19 to 196 MPa to form a pressure fired body.

9. A method for manufacturing a transparent ceramic material, comprising:

the first step (1) of subjecting an aqueous solution containing (d) terbium ion and (e) at least one rare earth ion selected from among yttrium ion, scandium ion, and lanthanide rare earth ion to co-precipitation, filtration and calcining to form a powder mix having a mean primary particle size of 30 to 2,000 nm, said powder mix containing at least 40% in molar fraction of terbium oxide and an oxide selected from among yttrium oxide, scandium oxide, and a lanthanide rare earth oxide,

the second step (2) of grinding and mixing the powder mix and a sintering aid which is an oxide, fluoride or nitride of an element selected from among titanium, zirconium, hafnium and calcium, and shaping the mixture into a green compact,

the third step (3) of firing the green compact at 1,400 to 1,700°

C. in a non-oxidizing atmosphere to form a fired body, and

the fourth step (4) of pressure firing the fired body at 1,400 to 1,800°

C. under a pressure of 19 to 196 MPa to form a pressure fired body.