JPS6210960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a forsterite single crystal that exhibits a green color due to the inclusion of nickel atoms, and a method for producing the same by concentrating infrared rays on a rod-shaped raw material.

[Conventional technology]

Forsterite is a type of olivine
It is known by its chemical formula Mg ₂ SiO ₄ . Mineralogically, it is sometimes used to perform ESR and Mossber measurements of Fe ²⁺ ions or transition metals in olivine [(Mg, Fe) ₂ SiO ₄ ]. Attempts to grow forsterite single crystals using the flux method, Bridgeman method, and pulling method have been reported. However, regarding forsterite solid solutions doped with transition metal ions, the only report is that Finch et al. grew crystals doped with Mn ²⁺ , Cr ³⁺ , and Fe ³⁺ , and no details were given. do not have. There are also reports of solid solution of Ni ions through solid phase reactions, but these do not concern single crystals.

[Problem that the invention seeks to solve]

As described above, the present invention aims to stably supply a single crystal of forsterite in a mass-produced manner, which has been desired but not realized in the past.

An object of the present invention is to provide a green transparent forsterite single crystal.

Another object of the present invention is to provide a green forsterite single crystal free of bubbles, inclusions, etc.

Still another object of the present invention is to provide a green forsterite single crystal by an easy and low-cost method.

[Means for solving problems]

a spheroidal mirror, a thermal light source disposed at one focal point of the spheroidal mirror, and an upper rotating shaft that pivotally supports a raw material rod (the raw material rod) disposed at the other focal point;
In a green forstellite single crystal manufacturing method using an infrared concentrated heating furnace device equipped with a lower rotating shaft that supports a seed crystal, and a transparent quartz tube that encloses the upper rotating shaft and the lower rotating shaft, MgCO ₃ . OH) ₂・5H ₂ O special grade reagent, SiO ₂ special grade reagent, and NiO special grade reagent were used as starting materials, and each raw material was weighed to have a composition of (Mg0.98・Ni0.02) ₂・SiO ₄ and mixed well. A firing reaction is carried out in the air at about 1150°C, and the mixture is further mixed in a mortar and formed into a rod shape using a rubber press, and then fired at about 1500°C to form the raw material rod, which is then placed on the upper rotating shaft. The raw material rod is held, the seed crystal is set on the lower rotating shaft, the tip of the raw material rod is melted, the melted portion is brought into contact with the seed crystal, and the upper rotating shaft and lower rotating shaft are mutually connected. It is characterized in that a single crystal is grown by moving the vertical rotation axis downward while rotating in the opposite direction.

The present inventor succeeded in obtaining a transparent single crystal uniformly colored in olive green to yellowish green by concentrating infrared rays on a rod-shaped raw material containing Ni ²⁺ in the forsterite composition and crystallizing it. A similar colored crystal is known as olivine in nature, but it is extremely rare. The green forsterite single crystal according to the present invention is free of color unevenness, color shading, bubbles, inclusions, etc., and is easily obtained.

First, the infrared heating furnace apparatus will be explained according to FIG. 1. The spheroidal mirror body 1 has two focal points. A halogen lamp 2 or a xenon lamp is placed at one focal point, and a rod-shaped raw material 3 is placed at the other focal point. The rod-shaped raw material 3 is held by an upper rotating shaft 4.
Further, the seed crystal 5 is set on the lower rotating shaft 6. The rod-shaped raw material 3, the seed crystal 5, and the upper and lower rotating shafts 4 and 6 are enclosed in a transparent quartz tube 7, so that the atmosphere can be freely controlled, and it is also possible to use vacuum or pressurization. The temperature rises in the rod-shaped raw material 3 and a molten zone 8 is formed only in the portion that completely coincides with the focal point. The melting zone 8 is relatively moved by moving the rotating shafts 4 and 6 upward or downward. In the operation, first, infrared rays are focused on the tip of the raw material rod 3 to form a molten zone 8, and then the seed crystal 5 is moved up and down to come into contact with the molten zone 8. After confirming that an equilibrium state has been reached, the rotating shafts 4 and 6 are moved, and a transparent single crystal is obtained with the seed crystal 5 growing. That is, melting of the raw material occurs at the interface between the melting zone 8 and the raw material rod 3, and crystallization occurs at the interface between the melting zone 8 and the seed crystal 5.

In addition, the formation of a molten zone is 1900° with a halogen lamp.
In the present invention, a halogen lamp is used to carry out the process, since it can be carried out up to 2800°C with a xenon lamp.

This method is most suitable for the present invention because it has the following features and advantages.

1. Operational safety is extremely high as high temperatures can be easily obtained. For example, the Bernoulli method requires sophisticated techniques because it uses oxygen gas and hydrogen gas, and is always exposed to the danger of explosion, but this method is easy to operate and does not require any special experience or technique. , and there is no danger at all.

2. Because the atmosphere and pressure can be controlled, compounds that are easily decomposed or easily oxidized can be easily crystallized.

3. Since heating is performed using infrared rays, it is possible to grow single crystals such as oxides that cannot be heated by high frequency induction heating. Naturally, since a crucible is not used, there is very little contamination of impurities. The formation of a molten zone can be performed up to 1900°C with a halogen lamp and up to 2800°C with a xenon lamp, so a halogen lamp is used in the present invention.

4. Halogen lamps and xenon lamps have very stable output and are very easy to control. Therefore, the molten zone is also very stable, and crystallization can be carried out without necessarily using seed crystals.

5. Since the melting state can be monitored, the state of crystal growth can be observed.

Next, the rod-shaped raw material is used by high-density sintering of raw material powder. The raw material powder used is one that has reacted to become forsterite, and a rubber press is usually used for molding. Here, approximately 1150° C. is the temperature at which the reaction of the raw material powder is completed, and the fired material is porous, contains amorphous shapes and crystals, and remains easily pulverized. Also, at approximately 1500℃, it becomes a complete sintered body (ceramic).
This is the temperature.

Furthermore, by setting the molar ratio of Mg to Ni to around 0.98 to 0.02, green forsterite with a vivid green appearance can be obtained.

〔Example〕

The present invention will be explained below with reference to Examples.

Mg(CO ₃ )・(OH) ₂・5H ₂ O (basic magnesium carbonate) special grade reagent, SiO ₂ special grade reagent, and NiO special grade reagent are used as starting materials, and each raw material (Mg0.98・
Ni0.02) _{2.SiO 4} was weighed, mixed well, and fired in air at 1150°C for 24 hours. After that, mix well in a mortar and use a 80mm x 85mm
It was molded using a rubber press method under a hydrostatic pressure of 750 kg/cm ² to a diameter of mm, and then baked at 1500° C. for 3 hours. This was used as a raw material rod and a seed rod. The seed crystal used was one made from a polycrystalline body into a single crystal and cut out in an appropriate orientation by the backside Laue method.
The equipment used was a bi-elliptical infrared concentrated heating single crystal manufacturing equipment using two halogen lamps (1.5KW). The atmosphere had an air flow rate of 70/hr. The rotation speed was 40 rpm for the raw material rod and the seed crystal in opposite directions.
The growth rate was 3.5 mm/hr. The melt remained stable during growth. The obtained crystal was a yellow-green transparent single crystal. No twins, bubbles, or inclusions were observed. The results of X-ray diffraction also confirmed that it was a forsterite single crystal. The lattice constant is a ₀ =
They were 4.775 angstroms, b ₀ = 10.202 angstroms, and c ₀ = 5.985 angstroms.
The ionic radius of Ni ²⁺ is 0.74 angstroms,
Since Mg ²⁺ ions have a thickness of 0.75 angstroms, it seems that there is almost no change in the lattice constant even if Ni ²⁺ ions replace Mg ²⁺ ions. The hardness was 6.5 to 7, harder than rutile and slightly softer than quartz.

〔Effect of the invention〕

As described above, the present invention has the following effects.

(1) By using basic magnesium carbonate (MgCO ₃ . (OH) ₂ .5H ₂ O) as a starting material, basic magnesium carbonate has higher chemical reactivity than magnesium oxide, and therefore, During the sintering process, the reaction of 2MgO + SiO ₂ →Mg ₂ SiO ₄ progresses faster and more completely, so the subsequent melting single crystallization process proceeds uniformly, allowing the growth of large single crystals with extremely high perfection. .

(2) To obtain a uniform green color, the single crystal must be uniformly doped with Ni. Therefore, it is absolutely necessary to cause a solid phase reaction during firing of the raw material rod. In order to cause this uniform solid phase reaction, a combination of NiO powder and basic magnesium carbonate is best because the chemical reaction activity of the two is extremely high.

(3) Since the upper rotation axis and the lower rotation axis rotate in opposite directions, by mixing well, a uniform green single crystal can be obtained, and even if it is repeatedly produced, there will be no variation.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the method of the present invention. 1...Spheroidal mirror body, 2...Halogen lamp,
3... Rod-shaped raw material, 4... Upper rotating shaft, 5... Seed crystal, 6... Lower rotating shaft, 7... Quartz tube, 8...
Melting zone.

Claims (1)

[Scope of Claims] 1. A spheroidal body, a thermal light source disposed at one focal point of the spheroidal body, an upper rotating shaft for supporting a raw material rod disposed at the other focal point, and a seed crystal. In a green forstellite single crystal manufacturing method using an infrared concentrated heating furnace device equipped with a lower rotating shaft that supports MgCO ₃ (OH) and a transparent quartz tube that encloses the upper rotating shaft and the lower rotating shaft, Using ₂・5H ₂ O special grade reagent, SiO ₂ special grade reagent, and NiO special grade reagent as starting materials, weigh each raw material so that it has a composition of (Mg0.98・Ni0.02) ₂・SiO ₄ , mix well, and A firing reaction is carried out in the air at about 1150°C, and the mixture is further mixed in a mortar and formed into a rod shape using a rubber press, and then fired at about 1500°C to form the raw material rod. A raw material rod is held, the seed crystal is set on the lower rotating shaft, the tip of the raw material rod is melted, the melted part is brought into contact with the seed crystal, and the upper rotating shaft and lower rotating shaft are rotated in opposite directions. 1. A method for producing a green forsterite single crystal, comprising growing the single crystal by moving the vertical rotation axis downward while rotating the single crystal in a direction.