JPS61215297A - Yttrium-iron garnet single crystal ingot - Google Patents

Abstract

PURPOSE:To reduce the crystal strain of a YIG single crystal ingot produced by the traveling solvent floating zone process, by adding two or more kinds of bivalent nonmagnetic ion to a sintered composition used as the raw material. CONSTITUTION:Yttrium iron garnet single crystal ingot is produced by converting a sintered composition composed mainly of yttrium iron garnet to a single crystal by traveling solvent floating zone process. In the above process, a sintered composition containing 0.1X10<-3>-3X10<-3>mol of two or more kinds of ions selected from Mo, Ca, Sr, Ba, Pb, Zn and Cd per 1mol of the composition is used as the raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a yttrium iron garnet single crystal ingot for use in optical elements with reduced transmission loss in the optical communication wavelength range and low crystal distortion.

[Prior art 1] Conventionally, the slack method and the traveling solvert floating zone method (hereinafter referred to as rTsFZ method) are known as methods for producing yttrium iron garnet (hereinafter referred to as rYIG) single crystal ingots. .

In the flux method, a YIG raw material is dissolved in 7Lx such as lead oxide having a low melting point, and a Y[G single crystal is precipitated by slow cooling or the like. This method has drawbacks, such as the fact that flux is likely to be contained in the crystal as an impurity, resulting in poor crystal uniformity, poor manufacturing yield, and the time it takes to grow the crystal. Furthermore, although the TSFZ method has good uniformity and reproducibility of crystal quality, the light transmittance in the 1.3 μ-band is lower than that produced by the flux method, making it undesirable as an optical element. Furthermore, the light transmittance varies greatly depending on the vertical position of the ingot, making it difficult to produce many elements that require high light transmittance, and making it impossible to ensure uniform quality.

In the TSFZ method, since the crystal growth temperature is as high as 1500° C. or higher, oxygen vacancies are generated in the grown YIG single crystal, and as a result, divalent iron ions are mixed with trivalent iron ions. This results in a decrease in light transmittance and longitudinal non-uniformity of the ingot. As a method to improve this problem, a method is known in which one of Ca, Zn, and Pb ions is mixed into the YIG composition as a raw material (Japanese Patent Laid-Open No. 53
-54700), this method is suitable for divalent ca, zn.

This is intended to suppress the generation of divalent Fe ions by causing Pb ions to capture surplus electrons due to oxygen vacancies instead of trivalent l''e ions.

[Problems to be solved by the invention] However, Ca1Z is added to the composition containing YIG as the main component.
If only one type of n or Pb ion is mixed, the ion itself will absorb light, which is not desirable as an optical element. Furthermore, distortion occurs in the grown crystal due to misfit between the YIG crystal lattice and the added ions. Furthermore, the types of ions that can be used to minimize these drawbacks are limited to the above-mentioned type 31a, and the mixing ratio thereof is also limited.

Therefore, the present invention has been made to solve the above-mentioned drawbacks, and by mixing a plurality of different types of ions, the light absorption specific to each ion is suppressed, resulting in low light transmittance loss and crystal distortion. The purpose is to provide a small amount of YIG single crystal.

[Technical means and effects for solving the problems] The present invention provides a yttrium iron garnet single crystal formed by single crystallizing a sintered composition containing yttrium iron garnet as a main component by a traveling solvert floating zone method. In the ingot, the sintered composition contains Mg, Qa, 3r, 3a, Pb, Z
The molar ratio of two or more ions of n and Cd is 0. lX
This is a yttrium iron garnet single crystal ingot for optical elements, characterized in that it contains 10-3 to 3X10-3.

Here, the type of additive element is a divalent nonmagnetic ion, YIG
We selected a material that dissolves solidly in the crystal. The amount of added elements mixed into the raw material sintered composition varies depending on the concentration of oxygen vacancies generated during crystal growth, but as a result of experiments, the total amount of added elements per mole of YIG is is 0. l
An improvement in light transmittance was observed when the amount was 3 to 3 x 10'''3 mol.

If the total amount added is too large, it will conversely inhibit the generation of Fe4+ and the light transmission properties will deteriorate, and since there is a limit to the amount of N-converting solvent, there is an upper limit to its value. Therefore, the addition ratio of the above-mentioned additional elements is preferably within the above-mentioned range.

Further, these additional elements are converted into M into yttrium site or ferrousite in the YIG crystal. If the size of each added ion is different from that of yttrium ion and iron ion, if each ion is added alone, it may not be replaced if added in a large amount, or even if it is replaced, distortion may easily occur in the crystal. Crystal defects and cracks occur. However, according to the present invention, by adjusting the blending ratio of two or more additive elements with different ion sizes, the misfits in the crystal lattice are averaged, the consistency of the entire crystal is improved, and the strain in the crystal is As a result, the occurrence of cracks can be reduced. Therefore, the mixing ratio of additive elements can be increased, and the generation of divalent Fe ions in the YIG single crystal can be prevented, so that light transmission loss can be reduced.

Also, mixing two or more types of additive elements is 1. By reducing the absolute mixing amount of each additive element, suppressing the unique light absorption peak newly generated by the additive element, and dispersing the light absorption wavelength, suppressing the newly generated light transmission loss of the entire crystal. It is.

``The above effect is the same when using a part of yttrium among the IG crystals. .

[Example 1] FIG. 1 is a schematic diagram of a single crystal manufacturing apparatus used for manufacturing an ingot of the present invention. 1 is a spheroidal mirror with one focal point F1
A halogen lamp 5 is installed at the other focal point F2, and at the other focal point F2,
A melting zone 3 is provided in which the lower end of the raw material rod 2 and the upper end of the seed crystal rod 4 are brought close to each other. The raw material rod 2 is fixed to the upper shaft 7a, and the seed crystal rod 4 is fixed to the lower shaft 7b. Both shafts 7a17b can move downward while rotating.

The raw material rod 2 is produced as follows.

YzO3 with a purity of 99.9% or more and l:eto3 are weighed so that the molar ratio is 3:5. In addition, 211i metal ions of MO and Ba total 062×10''3~6
A compound containing these metal ions is weighed and added in an amount of X10-3 moles.

That is, yttrium-iron-garnet (Y3Fe5O1
2) MQ and Ba ions are combined and 0.0% per 1 mole. l
Various blended powders containing X1 x 10-3 moles were prepared. However, the molar ratio of Mg and Ba was 1:1.

These raw material powders were mixed, molded, and sintered to produce raw material rods 2 having various blending ratios. The sintering temperature is 1,400° C. or higher, preferably 1,500° C. or higher, although it depends on the type of added element, and it is preferable to sinter in an oxygen atmosphere.

The melting zone 3 is formed by attaching a separately prepared material to serve as a solvent to the raw material rod 2 or the seed crystal rod 4 and heating and melting the material. While rotating the upper and lower shafts 7a and 7b in this manner, 1. Move downward at the speed of Osu+/hour YIG
Single crystals were grown.

In this way, a YIG single crystal ingot was produced, cut into pieces, the wafer was taken out, and 11 end faces were polished.
The light transmittance of the YIG single crystal with respect to the blending ratio of MQ, Ba, and ions was measured by irradiating it with μm light. The results are shown in FIG. As can be seen from this figure, the total amount of added elements is O, lXl0-3 to 3X10-3 for 1 mole of YIG.
In the molar range, a light transmittance of 65% or more was obtained.

The light transmittance is 1vlo, and the total amount of Ba added is 1.25.
The maximum value was reached when X10-3 moles, and the value was 70%.

Further, the wavelength dependence characteristics of the light transmittance of a YIG single crystal with a total addition amount of lvl and Ba of 1.25 x 10 -3 mol and a YIG single crystal without element addition were measured. The results are shown in FIG. It can be seen that the Example YIG single crystal has a higher light transmittance than the Comparative Example YIG single crystal without additives, and a light transmittance of 70% or more is obtained at 1.15 μm or more.

Next, Comparative Example YI in which only 1X10-3 mol of Ba was blended
G single crystal ingot, 3a and MO are 1=1, totaling 1
YrG single crystal ingots containing 3 mol of YrG were prepared, wafers were cut from them, and the number of cracks in the crystals was measured. The number of taratuks was compared within the cross section perpendicular to the growth direction. The results are shown in the table. As can be seen from the table, it can be seen that the addition of two types of elements with different ionic radii reduces the occurrence of cracks, rather than the addition of a single element with a large ionic radius.

(Other Examples) For 1 mole of YIG, the molar ratio of tvlo and SrO is 2
A YIG single-crystal ingot was produced using a sintered composition containing 10 −3 mol of YIG=1 as a raw material. Light transmittance and number of cracks were measured in the same manner as above. The light transmittance was improved compared to the case where no element was added, and the number of cracks was also reduced.

[Effects of the Invention] The present invention provides a YIG single crystal ingot produced by the traveling solvert floating zone method, in which two or more types of
This is a YIG single crystal ingot manufactured by blending valent non-magnetic ions.

Therefore, according to the present invention, since the blending ratio of two or more additive elements with different ion sizes is adjusted, the misfits in the crystal lattice are averaged, and the consistency of the entire crystal is improved. This reduces distortion and reduces the occurrence of cracks. Therefore, the mixing ratio of additive elements can be increased, and the generation of 2fIJ Fe ions in the YIG single crystal can be prevented, so that light transmission loss can be reduced.

In addition, since two or more types of additive elements are blended, the absolute amount of each additive element mixed can be reduced, suppressing the unique light absorption peak newly generated by the additive element, and dispersing the light absorption wavelength. Therefore, it is possible to suppress the newly occurring light transmission loss of the entire crystal.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a YIG single crystal ingot manufacturing apparatus of the present invention, and FIG. 2 is a YIG single crystal ingot manufacturing apparatus according to an embodiment.
YIG without added elements to change the wavelength characteristics of single crystal light transmittance
FIG. 3 is a characteristic diagram showing the light transmittance of the YIG single crystal according to the example as a function of the compounding ratio of added elements. 1... Ellipsoid of revolution l112... Raw material rod 3... Melting zone 4... Seed crystal rod 5... Halogen lamp 7a, b... Shaft Patent applicant Nippondenso Co., Ltd. agent Patent attorney Hirodo Okawa Patent Attorney Shudo Fujitani Patent Attorney Akio Maruyama

Claims (1)

[Claims] In a yttrium iron garnet single crystal ingot obtained by single crystallizing a sintered composition containing yttrium iron garnet as a main component by a traveling solvert floating zone method, the sintered composition contains Mg, C,
A, Sr, Ba, Pb, Zn, Cd, two or more ions in a molar ratio of 0.1 x 10^-^3 to 3 x 10^-
An yttrium iron garnet single crystal ingot for optical elements characterized by containing ^3.