WO2007052632A1

WO2007052632A1 - PROCESS FOR PRODUCING RUTILE (TiO2) SINGLE CRYSTAL, RUTILE (TiO2) SINGLE CRYSTAL, AND OPTICAL ISOLATOR COMPRISING THE SAME

Info

Publication number: WO2007052632A1
Application number: PCT/JP2006/321705
Authority: WO
Inventors: Isao Tanaka; Satoshi Watauchi; Shinsuke Morimoto; Jongkwan Pak
Original assignee: University Of Yamanashi
Priority date: 2005-11-01
Filing date: 2006-10-31
Publication date: 2007-05-10
Also published as: JPWO2007052632A1; JP4882075B2

Abstract

A rutile (TiO2) single crystal having a high transmittance is produced without the need of conducting single crystal growth in a high-pressure oxygen atmosphere or a heat treatment. The process for producing a rutile (TiO2) single crystal comprises melting a joint between a raw rutile rod and a seed rutile crystal to form a molten zone and growing a rutile (TiO2) single crystal while moving the molten zone. In the process, a different metal element which has a valance lower than that of the titanium, i.e., +4, is added to the molten zone, whereby the rutile (TiO2) single crystal which is being grown is inhibited from having an oxygen deficiency by the different metal element. Thus, a rutile (TiO2) single crystal in which the concentration of the different metal is 30 ppm or lower is produced.

Description

Specification

Method for producing rutile (TiO) single crystal, rutile (TiO) single crystal, and this

twenty two

Optical isolator using

Technical field

[0001] The present invention relates to a floaty using a rutile (TiO 2) single crystal, for example, using an infrared concentration heating furnace.

2

In particular, a rutile (TiO) single crystal having a light transmittance of 60% or more in a wavelength region of 420 nm or longer without the treatment of oxygen annealing or the like is manufactured. It is about how to do.

2

Background art

[0002] Rutile (TiO) single crystal is an indispensable optical material as a component of optical isolators.

2

is there. At present, rutile (TiO) single crystals are generally used in the floating zone method.

2

These are grown by the FZ method) or the Bernoulli method. However, crystal defects such as oxygen vacancies and small-angle grain boundaries are a major problem in the grown crystals.

[0003] The former causes a decrease in light transmittance and the latter causes a change in refractive index, both of which are rutile (TiO 2) single crystals.

This is a major obstacle when using 2 as an optical material. In addition, there is a problem that oxygen deficiency occurs at a high temperature and the color becomes dark blue. Furthermore, since the coloration associated with the oxygen crystals makes uniform heating difficult, it is difficult to grow a single crystal having a diameter of several inches.

[0004] As a method for suppressing the generation of low-angle grain boundaries, the growth atmosphere is grown under low oxygen partial pressure or high pressure oxygen pressurization in carbon dioxide gas or the like in crystal growth by the FZ method (Patent Document 1), or A method of adding metal ions such as Al ³⁺ and Sc ³⁺ to raw materials has been reported (Patent Document 2). The oxygen partial pressure 3 X 10- ² atm following crystal growth, colored dark blue by oxygen deficit occurs in the grown crystal, the length of the several tens of hours or more at 1000 ° C or more in order to reduce this oxygen deficiency It was necessary to perform oxygen heat treatment over time (Patent Document 1).

[0005] In Patent Document 2, as a method for producing a high-quality rutile single crystal having a large diameter and few lattice defects, a rutile (Ti 0) single crystal is grown using a sintered raw material rod containing an aluminum raw material.

2

The method is disclosed. However, according to the knowledge of the inventor, the rutile described in Patent Document 2 In the method for producing a single crystal, as the growth of the single crystal proceeds, aluminum accumulates in the molten zone, and a heterogeneous phase containing aluminum precipitates in the latter half of the grown crystal, resulting in a highly transparent rutile (TiO) single crystal. It was known that it was difficult to train.

2

Patent Document 1: JP-A-61-101495

Patent Document 2: Japanese Patent Laid-Open No. 6-48894

Disclosure of the invention

Problems to be solved by the invention

[0006] Rutile (TiO

2) A single crystal causes a decrease in light transmittance and a change in refractive index, and it is difficult to grow a single crystal having a large diameter. For this reason, it is necessary to grow single crystals under high-pressure oxygen pressurization as described above, or to perform oxygen heat treatment at 1000 ° C or higher for several tens of hours or more, which causes high costs. Yes.

Therefore, an object of the present invention is to bring a rutile (Ti 0) solvent or rutile melt (TiO 2) seed crystal containing a small amount of different metal elements into contact with a high-purity rutile raw material, Ti〇

twenty two

) Single crystal growth under high-pressure oxygen pressurization or single crystal growth

2

Providing a method for producing high-rutile, rutile (TiO) single crystals without the need for post-treatment heat treatment

2

There is to do.

Means for solving the problem

[0008] (1) In the present invention, in a predetermined growth atmosphere, a rutile raw material rod and a rutile seed crystal are melted to form a molten zone, and while the molten zone is moved, a rutile (TiO) unit is formed. Crystal

2 In the method for producing a rutile (TiO) single crystal to be grown,

2

A heterogeneous metal element having a valence lower than 4 is added, and oxygen vacancies in the grown rutile (TiO) single crystal are suppressed by the dissimilar metal element contained in the melting zone.

2

Use high purity rutile (Ti〇) sintered raw material rods and add different metal elements to the melting zone.

2

This makes it possible to produce transparent rutile (Ti〇) single crystals without heat treatment.

2

The This melts the oxygen deficiency of the rutile (TiO) single crystal where the different metal elements are grown

2

This is because different metal elements contained in the band are suppressed.

(2) It is preferable that the different metal element contained in the molten zone is one metal element selected from the group consisting of aluminum (A1), iron (Fe), calcium (Ca), and nickel (Ni). Also It is preferable that the growing atmosphere is oxygen 0. IMPa or more.

(3) The rutile (TiO) single crystal produced according to the present invention is in the wavelength region of 420 nm or more.

2

The light transmittance of the rutile (TiO) single crystal is 1 mm or more in the light transmission direction.

2

60% or more. In addition, rutile (TiO) produced by the present invention

2 The concentration of the dissimilar metal element contained in the single crystal is 30 ppm or less. This indicates that the foreign element contained in the liquid phase is not taken into the growing crystal, or that the proportion of the foreign element contained in the growing crystal is small. The concentration of the foreign element in the liquid phase is CL, and the concentration contained in the growing crystal is CS. This means that CS / CL is very small compared to 1.

(4) Therefore, even if dissimilar metal elements are dissolved in the rutile (TiO) single crystal, they are grown.

2

This means that different elements that dissolve in the crystal form a very small and uniform solution throughout the grown crystal.

The invention's effect

[0009] According to the present invention, a single crystal having low oxygen vacancies or small tilt grain boundaries and a norretyl (TiO 2) single crystal can be obtained.

2

Without the heat treatment at high temperature after growing the rutile (TiO) single crystal

2

High single crystals can be produced. As a result, it is possible to produce a large-diameter rutile (TiO) single crystal, which was impossible before.

2

Brief Description of Drawings

[0010] FIG. 1 is an explanatory diagram of a four-elliptic infrared intensive heating furnace used in a method for producing a rutile single crystal.

FIG. 2 is a diagram showing a bonding method (solvent attachment) between a solvent raw material and a rutile raw material and a method for growing a rutile single crystal.

FIG. 3 is a photograph of the color shape of the obtained grown crystal.

FIG. 4 is a graph showing the results of measuring light transmittance.

Explanation of symbols

[0011] 1 Four ellipse type infrared central heating device

11a, l ib spheroid mirror

12a, 12b infrared lamp

13 Quartz tube 14 Upper rotation axis

15 Lower rotation axis

16 Gas outlet

17 Gas inlet

18 Raw material bar

19 Melting zone

20 Rutile (TiO) seeding

2

21 screen

22 Lens

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is an explanatory view of a four-elliptic infrared central heating apparatus 1 used in the method for producing a rutile single crystal of the present invention.

[0013] In the four-elliptical infrared central heating apparatus 1 shown in FIG. 1, four spheroid mirrors l la and 1 lb are configured such that their respective focal points F coincide. Infrared lamps (for example, halogen lamps) 12a, 12b,... Are arranged at the other focal points Fa, Fb --- of each spheroid mirror lla, lib- ■.

[0014] At the position of the central focal point F, a melting zone 19 formed between the raw material rod 18 and the seed crystal 20 rotating in opposite directions is disposed. These are located in an infrared-transmitting cylindrical body 13 made of quartz glass or the like, and the raw material rod 18 and the seed crystal 20 are respectively coupled to an upper rotating shaft 14 and a lower rotating shaft 15 driven by a rotation driving mechanism. .

[0015] The raw material rod 18 is a cold isostatic press (CI) packed with TiO powder in a rubber tube.

2

It is made of a sintered body obtained by pressure molding with a 300MPa hydrostatic press according to P) and sintering in air at 1200 ° C for 12 hours.

A gas exhaust port 16 is communicated with the upper portion of the cylindrical body 13 and a gas inlet port 17 is communicated with the lower portion thereof, and oxygen is introduced from the gas inlet port 17 as a growing atmosphere in the cylindrical body 13. A constant oxygen pressure is maintained in the cylindrical body 13.

[0017] In the production of a rutile (TiO) single crystal, oxygen is supplied from the gas inlet 17 and 0.3 MPa In the above oxygen pressure, melt the lower end of the rutile raw material rod and the upper end of the rutile (Ti〇) seed crystal 20

2

After forming the melting zone 19, the melting zone 19 is moved by relatively moving the seed crystal 20 and the heating position at a speed of 3 mm / hour or more to cause rutile to crystallize in the seed crystal 20 to form a single crystal. obtain.

Example

[0018] A rutile raw material rod 18 was produced by the following procedure. Rutile raw material: Ti〇 (99.9%) (Toho Chitani)

2

(Made by UM Co., Ltd.) packed in a long and thin rubber tube, molded into a rod shape, vacuumed with an aspirator for 30 minutes to evacuate the tube, and 30 OMPa with a cold isostatic press (CIP) After forming with hydrostatic press, take out from rubber tube, drill a hole on one side, pass platinum wire, sinter in air at 1400 ° C for 12 hours in resistance heating furnace, and make round rod-shaped raw material rod 18 did. The size of the prepared raw material rod 18 is 7 to 9.5 mm in diameter and 45 to 60 mm in length.

[0019] The following solvent raw materials were prepared by the following procedure. First, as starting materials, Ti〇 (99.9%) (East

2 Japanese Titanium Co., Ltd.) was selected. In addition, as a foreign metal element added to the starting material, Al O (99.99%) (manufactured by Otsuchi Chemical Co., Ltd.), Fe O (99%) (manufactured by Kanto Chemical Co., Ltd.), Ni

2 3 2 3

0 (99.9%) (Wako Pure Chemical Industries, Ltd.), GaO (99.99%) (Rare Metallic, Inc.), CaCO (99.99%) (Rare Metallic, Inc.), YO (99.99%) (Inc. (Made of rare metal)

3 2 3

Was selected.

[0020] As shown in Table 1 in terms of metal atoms, each additive was wet mixed in an alumina mortar, placed in an alumina crucible, baked in air at 1000 ° C for 12 hours in a cantal furnace, and solvent powder. The powder was made.

[0021] The solvent powder is packed into a long and narrow rubber tube, molded into a rod shape, vacuumed for 30 minutes with an aspirator, and the air in the tube is evacuated, and a hydrostatic pressure of 300 MPa is applied by a cold isostatic press (CIP). After molding with a press, it was taken out from the rubber tube, drilled on one side, passed through a white wire, and sintered in air in a super cantal furnace at 1200 ° C for 12 hours to produce a sintered body of solvent raw material .

[0022] [Table 1] Solvent component Solvent concentration (ppm)

Al 13.5

1350

27000

Fe 70

700

Ca 750

Ni 300

Y 1700

Ga 1 75

[0023] A rutile single crystal growth apparatus was used for joining (solvent attachment) of the solvent raw material and the rutile raw material. This device is a four elliptical mirror type infrared condensing heating device 1 (FZ-T-4000-H manufactured by Crystal System Co., Ltd.) using four l.OkW halogen lamps as light sources. The quartz tube of this equipment was 2 mm thick when the growth atmosphere was oxygen O. lMPa, and 5 mm thick when oxygen was 0.5 MPa.

[0024] As shown in Fig. 2 (a), the raw material rod is fixed to the alumina tube with a platinum wire, 0.3 g of the solvent raw material is placed on the tip of the raw material rod (setting), and the atmosphere takes about 1.5 hours in the air. After increasing the lamp output to 172V and 18A (85%), the lamp voltage was adjusted to melt the solvent and attach the solvent raw material to the tip of the raw material rod (melting / solidification).

[0025] The growth conditions for the rutile single crystal were 5 mm / h at 1 atmosphere or 5 atmospheres of oxygen, and the rutile seed crystal 20 was a rutile single crystal grown in CO with an orientation <001> and a diameter of 3 mm. Figure 2

2

As shown in (b), the solvent-adhered material rod was hooked on the hook of the upper shaft with a platinum wire, and the rutile seed crystal 20 was installed on the lower shaft. After attaching the quartz tube, pressurize the oxygen pressure to an arbitrary value, increase the lamp output to 3.17 to 3.44 kW over about 1.5 hours, and rotate the upper and lower shafts in opposite directions at lOrpm (up) and 30 rpm (down) I let you. First, the tip of the raw material rod 18 was melted to form the melting zone 19 (FIG. 2 (b) melting). Thereafter, the seed crystal 20 was raised to the heating zone and the seed crystal 20 was heated, and then joined to the raw material rod 18 to form a melting zone 19 (see FIG. 2 (b) seeding). The heating zone was moved relatively upward at 5 mm / h to grow the rutile seed crystal 20 in the direction <001>. [0026] Here, the relative movement of the heating zone includes a method in which the heating furnace is moved upward and a method in which the raw material rod 18 and the seed crystal 20 are simultaneously moved downward, either of which may be used. During the growth, the lamp voltage was adjusted by looking at the situation in the melting zone 19 (Fig. 2 (b)). At the end of the growth, the ramp voltage was gradually decreased, and the grown crystal and the material rod 18 were separated in about 20 minutes (Fig. 2 (b) Melting zone separation).

[0027] Thereafter, the lamp output was set to 0 W over about 1 hour. The oxygen pressure was maintained until the lamp output was 0 W and the grown crystal was removed from the furnace.

[0028] The principle of the infrared ray condensing heating method used in this example is as follows.

[0029] A halogen lamp is placed at one focal point of a spheroid coated with an aluminum film or a gold film, and a seed crystal fixed to the tip of the raw material rod suspended on the upper shaft and the lower shaft at the other focal point. Arrange so that the top of 20 comes. By adjusting the voltage of the halogen lamp, the infrared light emitted from the halogen lamp at one focal point is condensed at the other focal point, melting part of the raw material rod 18 and seed crystal 20 and joining them together. Thus, a melting zone 19 is formed, and the melting zone 19 is sequentially moved upward to grow a single crystal.

[0030] The state of the melting zone 19 during the growth of the rutile (Ti 0) single crystal is shown in the growth apparatus drawing through the lens 22.

2

Since it is projected on the screen 21 of the surface, the stable melting zone 19 is maintained by adjusting the lamp voltage and the position of the upper and lower shafts while observing the melting zone. In addition, since the crystal growth section is shielded from the atmosphere by a transparent quartz tube, it is possible to grow crystals in any atmospheric gas. In addition, since a container such as a crucible is not required for forming the molten zone, there is no problem such as chemical reaction between the crucible and the raw material due to contamination from the crucible.

[0031] The shape of the grown crystal was a quadrangular prism because four facets appeared in parallel with the c-axis direction. There was a difference in the color of the grown crystal depending on the additive to the rutile solvent. As shown in Fig. 3, Al, Fe, and Ca were rutile's original pale yellow color regardless of the oxygen pressure in the growth atmosphere, but Ni is a neutral color between yellow and blue, and Y and Ga are slightly yellower than blue. It had a different color.

[0032] The grown rutile single crystal was cut into a wafer having a thickness of 2 mm parallel to <001>, and both surfaces were mirror-polished to lmm, and the quality was evaluated with a polarizing microscope. Figure 4 is a graph showing the results of measuring the light transmittance. The sample used here is l-2mm thick and polished Mirror-polished with lxm agent, unheat-treated. The UV_Spectrophotometer was used to measure the light transmittance in the 200 to 900 nm wavelength range at room temperature, and as shown in FIG. 4, the rutile (TiO) single crystal grown at an oxygen pressure of 0.5 MPa was 420 nm or more. wave

2

In contrast to the light transmittance of about 50% in the long region, when a solvent with Al or Fe added is used as the melting zone 19, it is approximately in the wavelength region of 420 nm or more without annealing. 60. /. Was obtained.

[0033] Solvent composition A11 350ppm, oxygen pressure O. lMPa grown rutile (TiO) crystal

2

Each sample was cut out with a sample, 0.1 g of a sample obtained by treating the tip of the grown crystal (0.252 g) and the latter half (0.208 g) in sulfuric acid at 90 ° C for 3.5 hours, weighed with alkali, and the molten salt was dissolved in hydrochloric acid. Dissolved in. Aluminum (A1) contained in this solution was measured by inductively coupled plasma optical emission spectrometry (device used: SPS-1700HVR type). As shown in Table 2, both Al and Fe were below the detection limit of the measuring device. .

[0034] Assuming that the dissimilar elements added to the molten zone are dissolved in the grown crystal, pure titanium oxide with no additive is used for the raw material rod. Therefore, the amount of different elements contained in the melt should decrease as the growth progresses. However, as this example shows, Al, Fe contained in rutile (TiO) crystal

2

Is below the detection limit, the manufactured rutile (TiO) single crystal has an initial part and an end part.

2

This is supported by the fact that there is no color difference.

[0035] [Table 2] Quantitative analysis results g / g)

Sample Fe AI

① Ku 20

② Ku 20 ―

③ ― 30

④ ― ku 20

⑤ 30 This specification is based on Japanese Patent Application No. 2005-318706 filed on Nov. 1, 2005. All this content is included here.

Claims

The scope of the claims

[1] A rutile that melts a joint between a rutile raw material rod and a rutile seed crystal in a predetermined growth atmosphere to form a melt zone, and grows a rutile (TiO 2) single crystal while moving the melt zone.

2

In the method for producing a (TiO 2) single crystal,

2

A rutile (TiO 2) single crystal grown by adding a dissimilar metal element having a lower valence than titanium valence + 4 to the molten zone, and growing by the dissimilar metal element contained in the molten zone

2. A method for producing a rutile (TiO 2) single crystal, characterized by suppressing oxygen deficiency 2.

2

2. The dissimilar metal element is one metal element selected from the group consisting of aluminum (A1), iron (Fe), calcium (Ca), and nickel (Ni). Method for producing rutile (TiO) single crystal.

2

[3] The method for producing a rutile (TiO) single crystal according to claim 1 or 2, wherein the growth atmosphere is oxygen of not more than 0.1 IMPa.

2

[4] Light transmittance power in the wavelength region of 420 nm or more Light transmission of the rutile (TiO) single crystal

2

The rutile (TiO) produced by the method for producing a rutile (TiO) single crystal according to any one of claims 1 to 3, wherein the thickness in the direction is at least 60% at lmm or more.

twenty two

) Single crystal.

[5] The concentration of the dissimilar metal element contained in the rutile (TiO) single crystal is 30 ppm or less.

2

A method for producing a rutile (TiO) single crystal according to any one of claims 1 to 3,

2

Rutile (TiO) single crystal produced by

2

[6] The rutile (Ti〇) melt in the container is contacted with the rutile (Ti〇) seed crystal in a predetermined growth atmosphere.

twenty two

In a method for producing a rutile (TiO) single crystal in which a rutile (TiO) single crystal is produced by touching

2 2 Add dissimilar metal element with lower valence than titanium valence + 4 in the rutile (Ti〇) melt.

2

And

Rutile (TiO) single crystal grown by the dissimilar metal element contained in the melting zone

2

7. The dissimilar metal element is one metal element selected from the group consisting of aluminum (A1), iron (Fe), calcium (Ca), and nickel (Ni). Rutile ( (TiO 2) Single crystal production method.

2

[8] The method for producing a rutile (TiO) single crystal as described in [6] or [7], wherein the growth atmosphere is oxygen at 0. IMPa or more.

2

[9] Light transmittance power in the wavelength region of 420 nm or more Light transmission of the rutile (TiO) single crystal

2

The rutile (TiO) produced by the method for producing a rutile (TiO) single crystal according to any one of claims 6 to 8, wherein the thickness in the direction is at least 60% at lmm or more.

twenty two

) Single crystal.

[10] The concentration of the dissimilar metal element contained in the rutile (TiO) single crystal is 30 ppm or less.

2

A method for producing a rutile (TiO 2) single crystal according to any one of claims 6 to 8,

2

Rutile (TiO) single crystal produced by

2

[11] TiO raw material rod by pressing and forming TiO powder and sintering at 1000 ° C or higher for a predetermined time

2 2

+ Pressurize 'TiO powder (hereinafter referred to as solvent powder) containing a trivalent or less dissimilar metal element,

2

A solvent raw material is produced by sintering at 1000 ° C or higher for a predetermined time,

The solvent raw material is dissolved and fixed to one end of the TiO raw material rod,

2

By a floating zone (FZ) method using an infrared intensive heating furnace, a melt zone is formed while melting the solvent raw material and the rutile seed crystal in a predetermined growth atmosphere, and the rutile ( Ti〇) By growing single crystals,

2

Rutile (Ti〇) characterized by suppressing oxygen deficiency in the grown rutile (Ti〇) single crystal

2

) A method for producing a single crystal.

2

12. The dissimilar metal element is one metal element selected from the group consisting of aluminum (A1), iron (Fe), calcium (Ca), and nickel (Ni). Of manufacturing rutile (TiO) single crystals.

2

[13] The method for producing a rutile (TiO) single crystal as described in [11] or [12], wherein the growth atmosphere is oxygen of 0.1 IMPa or more.

2

[14] Light transmittance power in the wavelength region of 420 nm or more Light transmission of the rutile (TiO) single crystal

2

The rutile (Ti) produced by the method for producing a rutile (TiO 2) single crystal according to any one of claims 11 to 13, characterized in that the thickness in the direction is 60% or more at a thickness of 1 mm or more. O) Single crystal.

2

[15] The concentration of the dissimilar metal element contained in the rutile (TiO) single crystal is 30 _PP m or less.

2

A method for producing a rutile (TiO) single crystal according to any one of claims 11 to 13,

2

Rutile (TiO) single crystal produced by

2

[16] An optical eye comprising the rutile (TiO) single crystal according to any one of claims 4, 5, 9, 10, 14, and 15.

2

Solator.