JPWO2006001225A1 - Corundum crystal former - Google Patents

Abstract

The main object of the present invention is to provide a corundum crystal formed body in which a corundum crystal is directly grown on a substrate, and a production method capable of easily and inexpensively manufacturing the corundum crystal formed body. . This invention solves the said subject by providing the corundum crystal formation body which has an alumina base material and the corundum crystal formed on the said alumina base material.

Description

  The present invention relates to a corundum crystal formed body that can be used for, for example, a material for high hardness, a cutting material, a laser oscillation material, a standard material for measuring physical properties, jewelry, and high-value-added daily necessities.

  Corundum crystals are excellent in chemical resistance, wear resistance, and weather resistance, and show high electrical insulation even in high-temperature environments. Therefore, corundum crystals are used for instrument bearings, micro scalpels, optical switch elements, or laser oscillation materials. It has been.

  Such corundum crystal production methods include (1) flame melting method (Bernoulli method) in which crystal grains are grown while dropping the raw powder of corundum crystal in oxygen and hydrogen flame, and (2) raw powder of corundum crystal Is mixed with an appropriate flux and melted in a crucible, and crystals are precipitated and grown while the solution is slowly cooled, or crystals are precipitated and grown while applying a temperature gradient in the crucible, or the flux is evaporated. (3) Czochralski method in which a raw material powder of corundum crystal is melted in a crucible and the crystal is pulled up from the melt (Patent Document 1) (See Patent Document 2), (4) A method of sintering a raw material powder of corundum crystals by heating at a high temperature for a long time in a hydrogen gas atmosphere (Patent Document 3) Irradiation), and the like.

  However, these methods are performed mainly for the purpose of producing the corundum crystals themselves, and there are few attempts to grow the corundum crystals directly on the substrate.

  For example, in the Czochralski method of (3) above, a crystal with high purity can be produced, and thus the obtained corundum crystal is suitably used for a laser oscillation material or the like. In this method, it is possible to fix a seed crystal on a substrate and grow a corundum crystal on the substrate with the seed crystal as a nucleus, but it is difficult to grow a corundum crystal directly on the substrate. .

  Further, in the flame melting method (1) and the method of sintering after molding (4), it is difficult to grow corundum crystals directly on the substrate.

  On the other hand, in the above flux method (2), it is assumed that the corundum crystal grows accidentally on the wall surface of the crucible, so it can be expected to grow the corundum crystal directly on the base material. Even if the corundum crystal grows on a part of the substrate, it is very difficult to form the corundum crystal in a desired part.

  Furthermore, although the corundum crystal obtained by the above-described method can be stuck on the substrate, there is a problem that the adhesion between the corundum crystal and the substrate is poor and the corundum crystal is easily peeled off.

  Among corundum crystals, dark red corundum crystals to which chromium is added are generally called ruby, but since natural ruby is produced in a relatively small amount, corundum crystals close to natural ruby are used on the base material. There is a need for a method that allows direct growth.

JP-A-7-277893 JP-A-6-199597 JP-A-7-187760 Elwell D., Man-made gemstones, Ellis Horwood Ltd., Chichester (1979) Elwell D., Scheel H. J., Crystal growth from high-temperature solutions, Academic Press, London (1975)

  The present invention has been made in view of the above problems, and a corundum crystal formed body in which a corundum crystal is directly grown on a substrate, and a manufacturing method capable of easily and inexpensively manufacturing the corundum crystal formed body. The main purpose is to provide

  In order to achieve the above object, the present invention provides a corundum crystal formed body comprising an alumina base material and a corundum crystal formed on the alumina base material.

  In the corundum crystal formed body of the present invention, the corundum crystal is directly formed on the alumina base material, and the corundum crystal is directly grown on the alumina base material. Therefore, the corundum crystal is pasted on the alumina base material. Unlike those, it has the advantage that the adhesive strength between the alumina substrate and the corundum crystal is strong, and can be used for various applications.

  In the above invention, the corundum crystal may be colorless. Alternatively, at least one element selected from the group consisting of chromium, iron, titanium, nickel, vanadium and cobalt may be added to the corundum crystal as a coloring component.

  Further, the present invention provides a corundum crystal formation characterized in that the flux and the alumina base material are heated to form a corundum crystal on the alumina base material by a flux evaporation method in which the crystal is deposited and grown using the evaporation of the flux as a driving force. A method for manufacturing a body is provided.

  In the present invention, since the alumina base material becomes a solute, it is possible to grow a corundum crystal directly on the alumina base material, and a corundum crystal formed body having a very strong adhesive force between the alumina base material and the corundum crystal. Can be manufactured. Further, in the flux evaporation method, the corundum crystal may contain elements contained in the flux as impurities, and a product close to natural corundum crystal is obtained. Can be manufactured. Furthermore, since the apparatus used in the flux evaporation method is simple and the manufacturing process is simple, a high value-added corundum crystal formed body can be provided at low cost.

  In the said invention, it is preferable that the said flux contains a molybdenum compound. The molybdenum compound is preferably molybdenum oxide or a compound that generates molybdenum oxide by heating. Since the molybdenum compound can be evaporated relatively easily, it is preferable as a flux used in the flux evaporation method.

  Moreover, in the said invention, the said flux may contain the evaporation inhibitor. This is because the evaporation rate of the flux can be suppressed and the generation of multinuclei and the crystal growth rate can be suppressed, so that a high-quality corundum crystal can be obtained.

  Furthermore, in the said invention, it is preferable that the said evaporation inhibitor is an alkali metal compound. The alkali metal compound is preferably an alkali metal oxide or a compound that generates an alkali metal oxide by heating. This is because by using these compounds, the evaporation of the flux can be effectively suppressed, and a high-quality and thick corundum crystal can be formed on the alumina substrate.

  According to the present invention, since the corundum crystal can be directly grown on the alumina base material by using the alumina base material as a solute by the flux evaporation method, there is an effect that the adhesive strength between the alumina base material and the corundum crystal is strong. Moreover, since a corundum crystal close to natural corundum crystals is obtained, the effect of high value as a jewelry or the like is achieved.

It is a schematic sectional drawing which shows an example of the corundum crystal formation body of this invention. It is a photograph which shows an example of the cross section of the corundum crystal formation body of this invention. It is a photograph which shows the other example of the cross section of the corundum crystal formation body of this invention. It is a diffraction diagram which shows an example of the X-ray-diffraction pattern of the corundum crystal in the corundum crystal formation body of this invention. It is process drawing which shows an example of the manufacturing method of the corundum crystal formation body of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Corundum crystal formation body 2 ... Alumina base material 3 ... Corundum crystal 4 ... Sample

  Hereinafter, the corundum crystal formed body of the present invention and the production method thereof will be described in detail.

A. Corundum crystal formed body First, the corundum crystal formed body of the present invention will be described.
The corundum crystal formed body of the present invention is characterized by having an alumina base material and a corundum crystal formed on the alumina base material.

  The corundum crystal formed body of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a corundum crystal formed body of the present invention. As shown in FIG. 1, a corundum crystal formed body 1 of the present invention has an alumina base 2 and a corundum crystal 3 formed on the alumina base 2.

Moreover, an example of the photograph which image | photographed the cross section of the corundum crystal formation body of this invention using the scanning electron microscope (the Hitachi Ltd. make, S-5000) is shown in FIG. 2 and FIG. As can be seen from FIG. 2 and FIG. 3, the corundum crystal formed body of the present invention has nothing between the alumina base material 2 and the corundum crystal 3, and the corundum crystal 3 directly on the alumina base material 2. Has grown. Therefore, the corundum crystal formed body of the present invention has the advantage that the adhesive strength between the alumina base material and the corundum crystal is different from that obtained by pasting the corundum crystal on the alumina base material, and can be used for various applications. It is.
FIG. 3 is a photograph showing an example of a cross section of a corundum crystal formed body having a corundum crystal to which chromium is added as a coloring component.
Hereinafter, each configuration of the corundum crystal formed body will be described.

1. Corundum Crystal First, the corundum crystal in the present invention will be described. The corundum crystal in the present invention is formed on an alumina substrate described later.

Here, the corundum crystal will be described. Corundum crystals have a corundum structure belonging to the trigonal system. In this corundum structure, cation (Al) regularly occupies 2/3 of the hexacoordinate (octahedron) position of the lattice that is almost hexagonally close packed, and AlO centered on the cation (Al). ₆ octahedrons share a part of the surface and are connected in the c-axis direction.

Corundum (Al ₂ O ₃ ) is the most stable among the alumina polymorphs, and the corundum crystal having such a corundum structure has a melting point of about 2050 ° C., a high hardness (Mohs hardness 9), and a chemical resistance Excellent in wear resistance, wear resistance and weather resistance. In addition, it exhibits high electrical insulation even in a high temperature environment. Because of such properties, corundum crystals are used for instrument bearings, micro-knives, optical switch elements, laser oscillation materials, and the like. In addition, by replacing a part of Al in corundum (Al ₂ O ₃ ) with Cr, Ti, Fe or the like, crystals with different hues are formed, and these crystals are generally called ruby or sapphire and are used as jewelry. It is used.

  The corundum crystal used in the present invention may be colorless or may contain at least one element selected from the group consisting of chromium, iron, titanium, nickel, vanadium and cobalt as a coloring component. . When the corundum crystal is added with a coloring component, the combination of the elements of the coloring component is not particularly limited. For example, chromium only; nickel only; vanadium only; cobalt only; iron and titanium; , Titanium and iron; chromium and nickel; chromium, nickel and iron; combinations of chromium, titanium and iron, and the like.

  Here, corundum crystals are known to have different hues depending on the type of coloring component such as chromium, iron or titanium. For example, those with no coloring component added are colorless, those with nickel added as a coloring component are yellow, those with vanadium added are alexandrite colors, those with cobalt added are green, iron and titanium added Is yellow, green with nickel, titanium and iron added, dark red, red or pink with chrome, chromium and nickel, or orange with chromium, nickel and iron, chrome, titanium And the one added with iron turns purple. In the present invention, a corundum crystal having the above hue can be obtained by combining elements as described above.

  In general, a dark red corundum crystal to which chromium is added is called ruby, and corundum crystals other than the red-added corundum crystal to which chromium is added are called sapphire. Natural ruby has a high rare value, and in the present invention, by adding chromium to the corundum crystal, a corundum crystal formed body having a red corundum crystal close to the natural corundum crystal can be obtained. , A high value-added corundum crystal formed body can be obtained.

  The addition of the above elements can be confirmed by EPMA (electron beam microanalyzer), XPS (X-ray photoelectron spectroscopy), or EDX (energy dispersive X-ray analysis).

  Further, the content of the element in the corundum crystal varies depending on the type of element, but is not particularly limited as long as the corundum crystal is colored in an amount sufficient to be colored. Also good.

  The composition of the corundum crystal is not limited to the stoichiometric one, but may be deviated from the stoichiometric composition. As will be described later, the corundum crystal formed body of the present invention is preferably produced by a flux evaporation method. When produced by the flux evaporation method, an element contained in the flux may be contained as an impurity in the corundum crystal. Because. The content of impurities in the corundum crystal is usually a very small amount of 1 mol% or less.

  Here, the corundum crystal can be identified using an X-ray diffractometer. At this time, a trigonal system, a = 4.759%, c = 12.993%, and JCPDS No. Compare with 46-1212. An example of an X-ray diffraction pattern of a corundum crystal to which chromium is added as a coloring component in the present invention is shown in FIG. FIG. 4A is an X-ray diffraction pattern measured by crushing to identify a corundum crystal. FIG. 4B shows JCPDS No. It is an X-ray diffraction pattern of 46-1212, and the X-ray diffraction patterns of FIGS. 4A and 4B were measured using CuKα rays.

  In the present invention, the corundum crystal formed body is preferably prepared by a flux evaporation method. This is because a corundum crystal can be formed using an alumina base material described later as a solute, and a corundum crystal can be formed directly on the alumina base material. Moreover, since the corundum crystal obtained by the flux evaporation method may contain an element contained in the flux as an impurity, it can be a crystal containing an impurity in the same manner as a natural corundum crystal, and as a jewelry etc. This is because it has the advantage of high value. Furthermore, the apparatus used in the flux evaporation method is simple as long as it has a high-temperature furnace, and corundum crystals can be easily obtained.

  Note that a corundum crystal forming method such as a flux evaporation method is described in the section of “B. Manufacturing method of corundum crystal formed body”, which will be described later, and thus the description thereof is omitted here.

  In the present invention, the corundum crystal may intentionally contain impurities. As mentioned above, it is because it has the advantage that it can be made close to nature by containing impurities, and has high value as a jewelery or the like.

  The corundum crystal may be formed on the entire surface of an alumina substrate described later, or may be formed in part. The formation position of such a corundum crystal is appropriately selected according to the use of the corundum crystal formed body of the present invention.

2. Next, the alumina substrate used in the present invention will be described. In the present invention, the alumina base material may be used alone, or the alumina base material and the base material may be laminated and used.

Such an alumina base material is not particularly limited as long as it has alumina as a main component, but it is preferable that the content of impurities with respect to alumina in the alumina base material is 5% or less. Is preferably 1% or less. This is because if the content of impurities relative to alumina is too large, there is a high possibility that impurities will be eluted when forming corundum crystals, and crystallization of corundum crystals may be hindered by the elution of these impurities. Examples of such impurities include general ones such as SiO ₂ , Na ₂ O, Fe ₂ O ₃ , CaO, MgO, and K ₂ O.

  In the present invention, when the alumina substrate and the substrate are laminated, the substrate used is not particularly limited as long as the alumina substrate can be formed and does not adversely affect the formation of the corundum crystal, It is preferable to be able to withstand the maximum holding temperature described in the section of the heating and evaporation step of “B. Method for producing corundum crystal formed body” described later. Examples of such a substrate include platinum, sapphire, alumina-silica, silicon carbide, and alumina. Since the alumina substrate is not required to have a low impurity content and high purity like the above-mentioned alumina substrate, it may be of low purity.

  In the above case, the alumina base material may be formed on the entire surface of the substrate, or may be partially formed. However, when it is partially formed, it is preferable to use platinum as the substrate. When a substrate of alumina is partially formed on a substrate other than platinum, when forming a corundum crystal, a part of the substrate may elute and adversely affect the formation of the corundum crystal. It is. Note that platinum has low reactivity with alumina and is considered not to affect the formation of corundum crystals.

  Further, when the alumina base material is partially formed on the platinum base material, a corundum crystal is formed on the alumina base material, and the corundum crystal is formed on the platinum base material on which the alumina base material is not formed. It is preferably not formed. This is because a corundum crystal formed body in which a corundum crystal is formed only in a desired portion can be obtained. Further, it is also possible to obtain a corundum crystal formed body having corundum crystals formed in a pattern by forming an alumina base material in a pattern on a platinum substrate.

  In addition to the above, when the platinum layer is formed in a pattern on the alumina base, or when the alumina base and the platinum layer are formed in a pattern on the base, the pattern A corundum crystal formed body having a shaped corundum crystal can be obtained.

  Examples of the method for forming the alumina substrate on the substrate include a physical vapor phase method such as a sputtering method and an electron beam (EB) method, an electrolysis method, and a compression molding method.

  Examples of the method for forming the platinum layer include general physical gas phase methods such as sputtering, ion plating, and vacuum deposition.

  In the present invention, when a corundum crystal is formed by a flux evaporation method described later, the alumina base material becomes a raw material for the corundum crystal, and the corundum crystal is formed by elution of alumina from the alumina base material. Therefore, the thickness and the size of the alumina base material are such thicknesses that can maintain the shape of the alumina base material even after the alumina is eluted from the alumina base material when the corundum crystal is formed using the flux evaporation method. And if it is a magnitude | size, it will not specifically limit, What is necessary is just to select suitably according to the use etc. of the corundum crystal formation body of this invention.

  The shape of the alumina substrate used in the present invention is not particularly limited, and is appropriately selected depending on the use of the corundum crystal formed body. For example, a container such as a crucible, a plate shape, a rod shape, a wire shape, a ring shape, a cube shape, an uneven shape, a spherical shape, a three-dimensional shape, a cone shape (cone, a pyramid, etc.), a column shape (a cylinder, a prismatic shape, etc.) can be mentioned. Moreover, it may be hollow, for example, between the nails of the ring or inside the mesh bag.

B. Next, a method for producing a corundum crystal formed body of the present invention will be described.
The method for producing a corundum crystal formed body according to the present invention includes forming a corundum crystal on an alumina substrate by heating the flux and the alumina substrate by a flux evaporation method in which the crystal is deposited and grown by using evaporation of the flux as a driving force. It is characterized by.

  The flux method is a kind of solution method and is also called a flux method. When growing a crystal by the flux method, an appropriate salt or oxide that becomes a flux and a raw material that becomes a solute are mixed, heated and melted, and then the solution is gradually cooled or a supersaturated state is created while the flux is evaporated. , Grow crystals. Depending on the difference in the method of forming this supersaturated state, it is roughly classified into a flux evaporation method, a flux slow cooling method, and a flux temperature gradient method.

  The present invention uses the flux evaporation method among the above. The flux evaporation method is a method for promoting nucleation and crystal growth using evaporation of flux as a driving force. For example, as shown in FIG. 5A, an alumina substrate 2 filled with a sample 4 containing flux. Is placed in the high-temperature furnace 12 and heated to evaporate the flux in the sample 4 to precipitate and grow the corundum crystal 3 on the inner wall of the crucible which is the alumina substrate 2 (FIG. 5B). )), A corundum crystal formed body 1 is obtained (FIG. 5C).

  Here, the mechanism by which corundum crystals are formed on the alumina substrate is considered as follows. That is, the alumina base material becomes a solute, and the alumina is gradually eluted from the surface of the alumina base material by heating the flux and the alumina base material, and is supersaturated at the interface between the alumina-eluting portion of the alumina base material and the evaporated flux. Therefore, it is assumed that corundum crystals precipitate and grow on the surface of the alumina base material.

  In this way, it is considered that corundum crystals precipitate and grow at a portion that becomes an interface between the alumina-eluting portion and the evaporated flux of the alumina base material. Therefore, for example, as shown in FIG. When the sample 4 containing the flux is filled in the crucible as shown in FIG. 5B, the interface between the portion of the alumina substrate 2 from which the alumina is eluted during the formation of the corundum crystal and the evaporated flux in the sample 4 is formed. Since the corundum crystal 3 is formed in the portion A, it is considered that the corundum crystal formed body 1 as shown in FIG. 5C is obtained.

  Thus, in the present invention, it is possible to grow corundum crystals directly on an alumina substrate by using the alumina substrate as a solute. Compared with the melting of the alumina powder used in the conventional flux method, the rate of elution of alumina from the alumina base material is slow, so it is possible to suppress the generation of polynuclears and the crystal growth rate, resulting in high quality. Corundum crystals can be obtained. Furthermore, since the corundum crystal is precipitated and grown with the alumina base material as a solute as described above, there is an advantage that a corundum crystal formed body having a very strong adhesive force between the alumina base material and the corundum crystal can be obtained.

  Here, there is a concern that the shape of the alumina base material changes if the amount of alumina eluted from the alumina base material is large. For example, a crucible made of alumina that can be used as an alumina base material is an alumina powder. Since it has a certain degree of heat resistance, a large amount of alumina is not easily eluted. Therefore, in the present invention, the amount of alumina eluted from the alumina base material is not so large as to change the shape or the like of the alumina base material, while maintaining the shape or the like of the alumina base material. Corundum crystals can be formed.

  Further, since the corundum crystals are formed even if the amount of alumina eluted from the alumina base material is small, the amount of alumina eluted may be small.

  Furthermore, in the present invention, since the flux evaporation method is used, the corundum crystal may contain an element contained in the flux as an impurity, and a product close to natural corundum crystal can be obtained. Can be produced.

  Further, as shown in FIG. 5 (a), the apparatus used for the flux evaporation method is simple as long as it has a high-temperature furnace 12, and when the flux is evaporated and crystals are precipitated and grown as described above, a corundum crystal is obtained. Therefore, the production process is simple, and a high value-added corundum bonded body can be produced at low cost.

The method for producing a corundum crystal formed body according to the present invention comprises a sample preparation step for preparing a sample containing a flux, heating the sample and the alumina substrate, and further evaporating the flux by maintaining the temperature at a high temperature. A heating / evaporation process for precipitating and growing corundum crystals, a cooling process for cooling the sample heated in the heating / evaporation process, and a sample remaining after the heating / evaporation process and the cooling process are dissolved in an appropriate medium. And a separation step of separating the corundum crystal formed body.
Hereinafter, each process of the manufacturing method of such a corundum crystal formed body will be described.

1. Sample Preparation Step In the method for producing a corundum crystal formed body of the present invention, a sample preparation step for preparing a sample containing a flux is first performed.

Although the sample used for this invention will not be specifically limited if it contains a flux, You may contain the additive for coloring. When the sample contains flux, colorless corundum crystals can be formed, and when the sample contains flux and coloring additives, colored corundum crystals can be formed. For example, when a chromium compound is used as an additive for coloring and the sample contains a flux and a chromium compound, a red corundum crystal can be formed.
Hereinafter, the flux and coloring additives will be described.

(1) Flux The flux used in the present invention is not particularly limited as long as it is evaporated in the heating / evaporation step described below and can be dissolved in an appropriate medium in the separation step described later. It is preferable to contain. This is because the molybdenum compound can be evaporated relatively easily and is suitable as a flux used in the flux evaporation method.

  As such a molybdenum compound, molybdenum oxide or a compound that generates molybdenum oxide by heating in a heating / evaporation process described later can be used. Examples of the compound that generates molybdenum oxide by heating include molybdenum carbonate, molybdenum sulfate, molybdenum nitrate, molybdenum hydroxide, and hydrates thereof. In the present invention, among these, molybdenum oxide is preferably used.

  In the present invention, the flux may contain an evaporation inhibitor. This is because the evaporation rate of the flux can be suppressed and the generation of multinuclei and the crystal growth rate can be suppressed, so that a high-quality corundum crystal can be obtained. Furthermore, as described above, the corundum crystal precipitates and grows by creating a supersaturated state at the interface between the part where the alumina is eluted from the alumina base and the flux that evaporates. Even if the corundum crystal is deposited in a certain part of the base material, it does not come into contact with the flux before it grows, and the corundum crystal may not grow any more. On the other hand, by suppressing the evaporation rate of the flux, it is possible to lengthen the time during which the alumina-eluting portion of the alumina base material is in contact with the flux. Can be formed.

  On the other hand, when the flux does not contain the above-described evaporation inhibitor, the flux evaporation rate is faster than when the evaporation inhibitor is contained, and the nucleation rate is faster, so that it is relatively thin on the alumina substrate. Corundum crystals can be formed.

  The evaporation inhibitor is not particularly limited as long as it can suppress the evaporation of the flux and can be dissolved in an appropriate medium in the separation step described later. In the present invention, an alkali metal compound is used. It is preferable. This is because by using an alkali metal compound, evaporation of the flux can be effectively suppressed, so that a high-quality and thick corundum crystal can be formed on the alumina substrate.

As such an alkali metal compound, an alkali metal oxide or a compound that generates an alkali metal oxide by heating in a heating / evaporation process described later can be used. As a compound which produces | generates an alkali metal oxide by said heating, an alkali metal carbonate, an alkali metal sulfate, an alkali metal nitrate, an alkali metal hydroxide, these hydrates, etc. are mentioned, for example. In the present invention, among the above, it is preferable to produce at least one alkali metal oxide selected from the group consisting of Li ₂ O, Na ₂ O and K ₂ O. _{Specifically, Li 2 CO 3, Na 2} CO 3, K 2 CO 3 and the like.

  In addition, the content of the alkali metal compound is such that the number of moles of alkali metal atoms of the alkali metal compound is 40 mol% or less, particularly 30 mol% or less, and particularly 20 mol% or less, based on the total number of moles of the sample. It is preferable to contain. In the present invention, nucleation and crystal growth are promoted by the evaporation of flux as a driving force, so that if the content of the alkali metal compound is too large, crystallization may be hindered.

(2) Coloring additive Next, the coloring additive used in the present invention will be described. The coloring additive used in the present invention varies depending on the coloring component added to the corundum crystal as described in the above-mentioned section “A. Corundum crystal forming body”, and is appropriately selected and used. . For example, when a colorless corundum crystal is formed, a coloring additive is not necessary. For example, when forming a corundum crystal to which iron and titanium are added as coloring components, iron compounds and titanium compounds are used as coloring additives. Further, for example, when forming a corundum crystal to which chromium is added as a coloring component, a chromium compound is used as an additive for coloring, and when forming a corundum crystal to which chromium and nickel are added as coloring components, As the coloring additive, a chromium compound and a nickel compound are used.
Hereinafter, iron and titanium-added corundum crystals and chromium-added corundum crystals will be exemplified.

(Iron and titanium added corundum crystal)
In the present invention, when forming a corundum crystal to which iron and titanium are added as coloring components, an iron compound and a titanium compound are used as coloring additives.

  The iron compound is not particularly limited as long as it is melted in the heating / evaporation process described later, but is preferably a compound that generates iron ions by heating. Examples of the compound that generates iron ions by heating are iron oxide, iron hydroxide, iron sulfate, iron carbonate, iron nitrate, iron chloride, iron citrate, iron phosphate, iron fluoride, iron iodide, Examples thereof include iron acids and hydrates thereof. Of these, iron oxide is preferably used in the present invention. In this case, the valence of iron in the iron oxide may be divalent or trivalent, and divalent and trivalent iron may be mixed.

  The titanium compound is not particularly limited as long as it melts in a heating / evaporation process described later, but is preferably a compound that generates titanium ions by heating. Examples of the compound that generates titanium ions by heating include titanium oxide, titanium nitride, titanium tetraisopropoxide, titanium oxalate, titanium sulfide, titanium bromide, titanium chloride, and hydrates thereof. . Of these, titanium oxide is preferably used in the present invention. In this case, the valence of titanium in the titanium oxide includes divalent, trivalent and tetravalent. The valence of titanium may be single or mixed.

  The addition amount of the iron compound and the titanium compound is not particularly limited as long as an amount sufficient to color the corundum crystals is added.

  In addition, the mixing ratio of the iron compound and the titanium compound varies depending on the valences of iron and titanium, but usually the weight ratio of the iron element and the titanium element is Fe: Ti = 1: 0.05-20. Mix like so. Among them, it is preferable to mix so as to be 1: 0.07 to 15, particularly 1: 0.1 to 10. This is because a corundum crystal colored bright blue can be obtained by setting the mixing ratio in the above range.

(Chromium-added corundum crystal)
In the present invention, when forming a corundum crystal to which chromium is added as a coloring component, a chromium compound is used as the coloring additive.

  The chromium compound is not particularly limited as long as it can be melted in the heating / evaporation process described later, but is preferably a compound that generates chromium ions by heating. As a compound which produces | generates chromium ion by said heating, chromium oxide, chromium hydroxide, chromium sulfate, chromium carbonate, chromium nitrate, these hydrates, etc. are mentioned, for example. Among them, it is preferable to use chromium oxide in the present invention.

  The addition amount of the chromium compound is not particularly limited as long as an amount sufficient to color the corundum crystals is added.

(Other corundum crystals)
In the present invention, when a corundum crystal to which nickel, vanadium or cobalt is added as a coloring component is formed, a nickel compound, vanadium compound or cobalt compound may be used as a coloring additive.

  The nickel compound is not particularly limited as long as it is melted in the heating / evaporation process described later, but is preferably a compound that generates nickel ions by heating. Examples of the compound that generates nickel ions by heating include nickel acetate, nickel carbonate, nickel chloride, nickel hydroxide, nickel iodide, nickel nitrate, nickel oxide, nickel sulfamate, nickel sulfate, and hydrates thereof. Etc. Among these, it is preferable to use nickel oxide. In this case, the valence of nickel in the nickel oxide may be bivalent or trivalent, and bivalent and trivalent nickel may be mixed.

  The vanadium compound is not particularly limited as long as it melts in a heating / evaporation process described later, but is preferably a compound that generates vanadium ions by heating. Examples of the compound that generates vanadium ions by heating include vanadium carbide, vanadium chloride, vanadium oxide, vanadium oxide sulfate, vanadium oxide oxalate, and hydrates thereof. Among these, it is preferable to use vanadium oxide. In this case, the valence of vanadium in the vanadium oxide includes trivalent, tetravalent, and pentavalent. The valence of vanadium may be single or mixed.

  Further, the cobalt compound is not particularly limited as long as it is melted in a heating / evaporation process described later, but is preferably a compound that generates cobalt ions by heating. Examples of the compound that generates cobalt ions by heating include cobalt bromide, cobalt chloride, cobalt citrate, cobalt fluoride, cobalt gluconate, cobalt hydroxide, cobalt iodide, cobalt nitrate, cobalt oxalate, and cobalt oxide. , Cobalt phosphate, cobalt stearate, cobalt sulfate, cobalt sulfide, and hydrates thereof. Among these, in the present invention, it is preferable to use cobalt citrate, cobalt fluoride, cobalt gluconate, cobalt hydroxide, cobalt iodide, cobalt oxalate, cobalt oxide, cobalt phosphate, and cobalt stearate. In particular, it is preferable to use cobalt oxide, cobalt hydroxide, cobalt stearate, and cobalt phosphate. In this case, the valence of cobalt in the cobalt compound may be bivalent or trivalent, and bivalent and trivalent cobalt may be mixed.

  The amount of the nickel compound, vanadium compound, or cobalt compound added is not particularly limited as long as an amount sufficient to color the corundum crystal is added.

  In the present invention, when forming a corundum crystal to which chromium and at least one element selected from the group consisting of iron, titanium, nickel, vanadium and cobalt are added as a coloring component, the above-mentioned chromium compound In addition, an iron compound, a titanium compound, a nickel compound, a vanadium compound, or a cobalt compound may be used.

  At this time, the addition amount of the iron compound, titanium compound, nickel compound, vanadium compound or cobalt compound described above is not particularly limited as long as an amount sufficient to color the corundum crystal is added.

  In the present invention, the above-mentioned iron compound, titanium compound, chromium compound, nickel compound, vanadium compound or cobalt compound can be used in various combinations, and the mixing ratio of these compounds depends on the application of the corundum crystal formed body. Are appropriately selected.

(3) Others When preparing a sample in this step, the flux and coloring additives are usually stirred. The stirring method is not particularly limited as long as it can uniformly stir, and for example, a method of sufficiently stirring the flux and coloring additive in a mortar can be mentioned.

  In the present invention, the sample may contain impurities. This is because crystals close to nature can be obtained, and corundum crystals having high value as jewelry can be formed.

  The sample may contain an aluminum compound. In the present invention, as described above, the alumina base material becomes a solute, and alumina is eluted from the surface to form a corundum crystal. However, an aluminum compound can be further contained as this solute. In this case, the content of the aluminum compound is appropriately adjusted in consideration of the balance between elution of alumina from the alumina base material and melting of the aluminum compound so as not to prevent the precipitation and growth of corundum crystals on the alumina base material. Is done. For example, if the content of the aluminum compound is too large, crystals may grow with the aluminum compound serving as a nucleus, and it may be difficult to form a corundum crystal on the alumina substrate.

  As such an aluminum compound, alumina (aluminum oxide) or a compound that generates alumina by heating in a heating / evaporation process described later can be used. As a compound which produces | generates an alumina by said heating, aluminum hydroxide, aluminum sulfate, aluminum carbonate, aluminum nitrate, and these hydrates etc. are mentioned, for example. Of these, alumina is preferably used in the present invention.

2. Next, the heating / evaporation process in the present invention will be described. The heating / evaporation step in the present invention is a step in which the sample and the alumina base material are heated, further maintained at a high temperature to evaporate the flux, and corundum crystals are deposited and grown on the alumina base material.

  In this step, for example, when a crucible made of alumina is used as the alumina base material, the lid 13 is covered with the crucible which is the alumina base material 2 filled with the sample 4 containing the flux as shown in FIG. And installed in the high temperature furnace 12. Next, when the temperature is raised to the maximum holding temperature and held at that temperature for a predetermined time, the flux in the sample 4 evaporates, and the alumina is eluted from the crucible which is the alumina base material 2 to drive the evaporation of this flux. As a force, the precipitation and growth of the corundum crystal 3 is promoted (FIG. 5B). Thereby, the corundum crystal formed body 1 in which the corundum crystal 3 is formed on the alumina base material 2 is manufactured (FIG. 5C).

  The maximum holding temperature in this step is not particularly limited as long as it is a temperature at which the flux evaporates, the coloring additive melts, and the alumina is eluted from the alumina base material, specifically, 950 ° C. to 1300 ° C., Among them, it is preferable that the temperature is in the range of 975 ° C to 1250 ° C, particularly 1000 ° C to 1200 ° C.

  Further, the rate of temperature rise at the time of setting the maximum holding temperature is not particularly limited as long as it is a rate that can uniformly heat the sample containing the flux and the coloring additive and the alumina base material. is not. Furthermore, the time for holding at the maximum holding temperature is not particularly limited as long as the corundum crystal can be sufficiently grown.

  The alumina base material is the same as that described in the above-mentioned section “A. Corundum crystal formed body”, and the description thereof is omitted here.

  In the present invention, the alumina base material is a container such as a crucible in which the sample is filled, and the sample may be placed in a container that is the alumina base material, or the alumina base material and the sample may be placed in the container. Good. When the alumina base material and the sample are placed in a container, the container used is not particularly limited as long as it can withstand the above-mentioned maximum holding temperature and has low reactivity with the sample. A container made of

  Further, in both cases where the sample is placed in a container that is an alumina base material, and where the alumina base material and the sample are placed in the container, the alumina base material and the sample are placed in contact with each other.

  In the present invention, as described above, the alumina base material becomes a solute, and alumina is gradually eluted from the surface of the alumina base material by heating, and is supersaturated at the interface between the part of the alumina base material from which alumina is eluted and the flux that evaporates. Since the state is created, it is considered that corundum crystals precipitate on the surface of the alumina base material and grow. From this, for example, when the crucible which is the alumina base material 2 as shown in FIG. 5A and the sample 4 containing the flux are heated, the flux evaporates from above, and as shown in FIG. 5B. Thus, it is assumed that the corundum crystal 3 is gradually formed from the upper side of the inner wall of the crucible which is the alumina base material 2.

  In addition, it is assumed that corundum crystals precipitate and grow only on the part of the alumina base material where the alumina is eluted and the flux that evaporates, so the flux is completely evaporated at the part where the corundum crystals are to be formed. It is required to do. For example, when it is desired to form a corundum crystal on the inner wall and the bottom surface of the crucible which is the alumina substrate 2 as shown in FIG. 3A, the flux is completely evaporated so that the flux does not remain on the bottom surface of the crucible. Good.

3. Next, the cooling process in the present invention will be described. The cooling step in the present invention is a step of cooling the sample heated in the heating / evaporating step.

  In this step, for example, the crucible which is the alumina base material 2 filled with the sample 4 containing the flux is taken out from the high temperature furnace 12 as shown in FIG. 5A and cooled to room temperature. As this cooling method, any method can be used as long as it can be cooled to room temperature, and examples include a method of cooling the crucible.

4). Next, the separation process in the present invention will be described. The separation step in the present invention is a step of separating the corundum crystal formed body by dissolving the sample remaining after the heating / evaporation step and the cooling step in an appropriate medium.

  In the present invention, a sample such as a flux remains after the cooling step such that the flux does not completely evaporate in the heating / evaporation step or the evaporation inhibitor remains undissolved. In this step, it is possible to easily separate only the corundum crystal formed body by dissolving these remaining samples in an appropriate medium.

  The medium used for dissolving the remaining sample is not particularly limited as long as it does not affect the corundum crystal and can dissolve the remaining sample other than the corundum crystal and the alumina substrate. Cold water, warm water, hot water, etc. can be mentioned.

  The corundum crystal formed by the method for producing a corundum crystal formed body of the present invention is the same as that described in the above-mentioned section “A. Corundum crystal formed body”, and thus the description thereof is omitted here. .

5. Others In the present invention, when an alumina substrate is partially formed on a platinum substrate as described in the above-mentioned section “A. Corundum crystal formed body”, platinum on which an alumina substrate is not formed Corundum crystals may also be formed on the substrate. In such a case, when producing a corundum crystal formed body in which a corundum crystal is not formed on a platinum substrate, by performing an acid melting treatment using an acid flux such as potassium hydrogen sulfate, Corundum crystals formed on the platinum substrate can be peeled off. Corundum crystals formed on the alumina substrate by the acid melting treatment are not peeled off. Thereby, a corundum crystal formed body in which a corundum crystal is formed only in a desired portion can be obtained.

  In addition, even when the platinum layer is formed in a pattern on the alumina base material, or when the alumina base material and the platinum layer are formed in a pattern shape on the base material, the above-described acid melting treatment can be used to form platinum. Corundum crystals formed on the layer can be peeled off.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same operational effects or their equivalents. Is included in the technical scope of the present invention.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
Iron oxide (0.004 g), titanium oxide (0.004 g), molybdenum oxide (28.5 g) and lithium carbonate (0.5 g) were weighed and placed in a mortar. This mixed sample was dry mixed in a mortar for about 20 minutes. Thereafter, the mixed sample was filled in an alumina crucible (purity 99.6%), capped, and placed in an electric furnace. The electric furnace was heated to 1100 ° C. at a rate of 45 ° C. per hour and held at that temperature for 5 hours. After the holding, the alumina crucible was taken out from the electric furnace and allowed to cool to room temperature. A photograph of the cross section of the obtained corundum crystal formed body is shown in FIG. As shown in FIG. 2, a corundum crystal 3 having a thickness of about 150 μm was formed on the inner wall of the alumina crucible 2.

[Example 2]
Chromium oxide (0.008 g), molybdenum oxide (28.5 g) and lithium carbonate (0.5 g) were weighed and placed in a mortar. This mixed sample was dry mixed in a mortar for about 20 minutes. Thereafter, the mixed sample was filled in an alumina crucible (purity 99.6%), capped, and placed in an electric furnace. The electric furnace was heated to 1100 ° C. at a rate of 45 ° C. per hour and held at that temperature for 5 hours. After the holding, the alumina crucible was taken out from the electric furnace and allowed to cool to room temperature. A photograph of the cross section of the obtained corundum crystal formed body is shown in FIG. As shown in FIG. 3, a red corundum crystal 3 having a thickness of about 150 μm was formed on the inner wall of the alumina crucible 2.

Claims (9)

  A corundum crystal formed body comprising an alumina base material and a corundum crystal formed on the alumina base material.   The corundum crystal formed body according to claim 1, wherein the corundum crystal is colorless.   2. The corundum crystal according to claim 1, wherein at least one element selected from the group consisting of chromium, iron, titanium, nickel, vanadium and cobalt is added as a coloring component. Corundum crystal formed body.   A method for producing a corundum crystal formed body, wherein a corundum crystal is formed on an alumina substrate by heating the flux and the alumina substrate by a flux evaporation method in which the evaporation of the flux is used as a driving force to precipitate and grow crystals.   The said flux contains a molybdenum compound, The manufacturing method of the corundum crystal formation body of Claim 4 characterized by the above-mentioned.   6. The method for producing a corundum crystal formed body according to claim 5, wherein the molybdenum compound is molybdenum oxide or a compound that generates molybdenum oxide by heating.   The said flux contains an evaporation inhibitor, The manufacturing method of the corundum crystal formation body of Claim 5 or Claim 6 characterized by the above-mentioned.   The method for producing a corundum crystal formed body according to claim 7, wherein the evaporation inhibitor is an alkali metal compound. The method for producing a corundum crystal formed body according to claim 8, wherein the alkali metal compound is an alkali metal oxide or a compound that generates an alkali metal oxide by heating.

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