RU2613520C1 - Polycrystalline synthetic jewelry material (versions) and method of its production - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: creating a polycrystalline jewelry material from coloured transparent or translucent oxide ceramics with dopants is proposed. The material consists of oxidic compounds which are represented by yttrium-aluminium garnet or magnesium aluminium spinel, for dying which ions of transition and rare earth metals: zinc, iron, vanadium, chromium, manganese, nickel, cobalt, titanium, neodymium, europium, terbium, ytterbium, holmium, erbium, thulium - are used. The method of manufacturing transparent or translucent ceramic comprises the stages of obtaining a powder mixture and annealing the components, hot uniaxial/cold isostatic pressing, hot isostatic pressing and heat treatment.

EFFECT: wider colour range of samples and possibility of obtaining colour effects caused by the activator concentration variable as per the pattern or the crystalline phases are achieved, the cost of goods is much less in comparison with the use of single-crystal material.

5 cl, 4 tbl, 2 ex

Description

The group of inventions relates to materials for the jewelry industry and involves the use as a synthetic material to simulate natural jewelry stones.

The manufacture of synthetic stones in our time is widespread. The discovery of technologies for the synthesis of jewelry stones for many decades has made jewelry more affordable, stones more advanced (maximum purity and color saturation), allows you to replace endangered natural stones, replacing them with artificial counterparts.

Conventionally, synthetic jewelry stones can be divided into three types. The first relate to those synthetic stones that have a natural analogue, such as ruby, corundum, sapphire, spinel, rutile, diamond, emerald, quartz, alexandrite, opal, etc. The second type combines artificial stones that have no natural analogues (lithium niobate, yttrium - aluminum garnet, cubic zirconia, etc.). They also separately distinguish the type of imitation of jewelry stones: glass, doublets and triplets.

Glass is the cheapest substitute in the jewelry industry. It is also transparent and is used to make inexpensive jewelry. Glasses differ from crystals in that their inherent amorphous structure deprives the material of total internal reflection, which gives bright shine to crystalline stones. The disadvantage of glass jewelry is its low hardness and low refractive index.

Analogs of natural precious and semiprecious stones have a crystalline structure, the preparation of which requires high energy costs. Currently, there are a number of traditional methods for producing synthetic materials to create such stones. These methods originate from 1892, when the French scientist Verneil developed a method for the synthesis of single-crystal ruby, and then other precious stones. Then the method was used to synthesize not only prototypes of natural crystals (rutile, quartz, diamond, emerald), but also exclusively artificial stones (fabulite, yttrium-aluminum garnet, cubic zirconia) [Tatarkhenko V.A. Sustainable crystal growth. - The science. Ch. ed. physical - mat. lit., 1988].

After the Verneuil method, other methods also related to melt synthesis processes followed: the Czochralski method, directional crystallization method, etc. Of course, when using these methods for individual compositions, individual conditions are selected, and the methods themselves undergo hardware and technological changes.

In the patent of the Russian Federation No. 2134314, published on 08/10/1999 according to the indices IPC C01G 25/02, C30B 11/02, C30B 29/16, C30B 29/22, a method for producing colored single crystals by growing from a melt by directional crystallization is claimed. The material consists of basic oxide (18-57 mol%), cobalt oxide (0.28-3 mol%), neodymium oxide (0.05-1.0 mol%) and zirconium or hafnium oxide. Annealing of the obtained single crystal is carried out in an inert gas atmosphere or in vacuum at temperatures of 500-1000 ° C for 0.5-5 hours. Thus, a close resemblance to natural gems is achieved.

In the patent of the Russian Federation No. 2178019, published January 10, 2002 according to the indices MPK С30В 29/18, С30В 7/10, a method for manufacturing colored quartz crystals is stated. The synthesis is carried out under hydrothermal conditions by recrystallization from an aqueous solution of sodium carbonate in the presence of cobalt and aluminum. The method allows to obtain crystals with a color close to sapphire.

From the patent of the Russian Federation No. 2473720, published on 01/27/2013 according to the indices MPK С30В 25/02, С30В 29/04, С23С 16/27, С30В 28/14, the possibility of using the CVD method as a method for producing a colorless diamond single crystal for the manufacture of jewelry stones is known. To obtain this effect, a nitrogen atmosphere with a boron content is used to reduce the negative effect of nitrogen on the color of diamond.

In RF patent No. 2328561, published July 10, 2008 according to the indices MPK С30В 15/04, С30В 29/28, С30В 33/02, А44С 17/00, a method for producing single-crystal terbium-gallium garnet by the Czochralski method is claimed. Calcium containing additives is added to the initial mixture, and after melting, it is pulled for seed in a hydrogen atmosphere at temperatures of 850-950 ° C for 5 hours. Such manipulations make it possible to obtain optically transparent and homogeneous crystals.

Another modification of the method based on the recrystallization process is described in CN patent No. 101407402, published April 15, 2009, IPC SB04/00. During the synthesis, various compositions, including coloring ions of chromium, iron, titanium, or nickel, are supplied to the crystal growth zone upon application of a temperature gradient. Thus, it is possible to achieve a color spectrum in the stone. To form a similar color effect, it is possible to modify the method of drawing from the melt by feeding a number of different compositions alternately into the melting zone, as proposed in GB patent No. 608453, published September 15, 1948 by the MPC indices C30 B11 / 10, C30 B29 / 26.

In GB patent No. 762142, published on November 21, 1956 according to the indices IPC С30В 11/10, С30В 29/26, G02B 1/02, the method for producing monocrystalline strontium titanate in the form of boules from white to blue by gas-flame crystallization is protected. A powder mixture containing the main component (strontium titanate) and up to 3 mol% is introduced into the flame of an oxygen / hydrogen burner. % dye ion (molybdenum, tungsten, uranium, niobium, tantalum, iron, vanadium, chromium, manganese, nickel, cobalt).

The technologies for producing single-crystal materials for the jewelry industry are characterized by high temperatures, long periods of synthesis cycles, and complex equipment designs. It is possible to simplify this process by moving from single crystals to polycrystalline materials.

RF patent No. 2426488, published on 08/20/2011 on the IPC indices A44C 17/00, A44C 27/00, protects the method of producing synthetic material for the jewelry industry based on nanopowders of oxides and silicates. The composition should include at least one of the presented phases: spinel, quartz and similar phases, sapphire, enstatite, petalite, cordierite, zircon, rutile, titanate and zirconia. Color is created by doping with rare earth ions. The method includes the stages of melting the initial mixture, cooling to 1300-1450 ° C, molding and annealing at 640-500 ° C. The resulting material is polycrystalline and has hardness and chemical resistance. However, the quality of the optical properties is markedly reduced.

The use of ceramic composites for jewelry is quite common. It is proposed to use ceramics based on zirconium oxide for the manufacture of watch bracelets. The synthesis method of such material protects the patent EP No. 2740717, published on 06/11/2014 by indices IPC С04В 35/117, С04В 35/119, С04В 35/488, С04В 35/626, С09С 1/00, C09D 1/00, selected as prototype for a group of inventions. A preform is formed from a mixture of powders, and then sintered at temperatures of 1200-1500 ° C.

Polycrystalline material imitating precious and semi-precious natural stones with high optical characteristics (spinel, yttrium-gadolinium or yttrium aluminum garnets, etc.) is not known from the prior art.

The objective of the invention is to provide a polycrystalline synthetic jewelry material from colored transparent oxide ceramics doped with transition and / or rare-earth metal ions.

The group of inventions is united by an inventive concept and includes synthetic jewelry materials and methods for their preparation.

The technical result is achieved by obtaining a polycrystalline synthetic jewelry material from colored transparent ceramic based on oxides in the form of yttrium aluminum garnet and in the form of aluminum-magnesium spinel alloyed with transition and / or rare-earth ions, which has the following general properties:

- Vickers microhardness from 1.29 to 1.35 MPa for transparent ceramics based on yttrium aluminum garnet and from 1275 to 1675 MPa for transparent ceramics based on aluminum-magnesium spinel;

- transmittance in the visible region of the spectrum of at least 50% for transparent ceramics based on yttrium aluminum garnet and at least 50% for transparent ceramics based on aluminum-magnesium spinel.

The first option relates to a polycrystalline synthetic jewelry material from colored transparent ceramics based on yttrium aluminum garnet doped with transition and / or rare-earth metal ions.

The composition of the charge: Y _3-x Me _x Al ₅ O ₁₂ , where Me is a metal dye, x = 0.00016-1.6, where x is a stoichiometric coefficient.

The creation of synthetic jewelry material from transparent ceramics (polycrystalline blanks) based on yttrium aluminum garnet of a wide color gamut is ensured by doping with transition and / or rare-earth metal ions (manganese, chromium, vanadium, thulium, nickel, cobalt, neodymium, erbium, terbium, europium, holmium, ytterbium) in the form of oxides in an amount of from 0.001 to 10 mol. %

The composition of the charge: Mg _1-x Me _x Al ₂ O ₄ , where Me is a metal dye, x = 0,00035-0.35, where x is a stoichiometric coefficient.

The creation of synthetic jewelry material from transparent ceramics (polycrystalline blanks) based on aluminum-magnesium spinel of a wide color gamut is ensured by alloying with transition and / or rare-earth metals (chromium, iron, manganese, cobalt, nickel, zinc, titanium) in the form of oxides in an amount from 0.005 to 5 mol. %

A method for producing a polycrystalline synthetic jewelry material from transparent ceramic based on yttrium aluminum garnet and transparent ceramic based on aluminum-magnesium spinel includes the following steps:

1) Heat treatment of a powdery mixture of the starting components, consisting of Y _3-x Me _x Al ₅ O ₁₂ or Mg _1-x Me _x Al ₂ O ₄ , at a temperature of 200-400 ° C for 2-6 hours.

2) Additional grinding of the heat-treated powder mixture in a planetary ball mill for 1-6 hours to obtain particles from 30 nm to 100 nm in size.

3) Hot uniaxial pressing of the crushed powder mixture to obtain a compressed billet in the form of a disk with a density of at least 99% of theoretical density, while:

- for a material based on yttrium aluminum garnet, hot uniaxial pressing is performed of a crushed powder mixture based on Y _3-x Me _x Al ₅ O ₁₂ at a temperature of 1450-1750 ° C and a pressure of 35-200 MPa;

- for a material based on aluminum-magnesium spinel, hot uniaxial pressing is performed of a crushed powder mixture based on Mg _1-x Me _x Al ₂ O ₄ at a temperature of 1400-1600 ° C and a pressure of 35-200 MPa.

The difference between the pressing modes at this stage is due to the different physicochemical properties of the compounds, on the basis of which a polycrystalline synthetic jewelry material will be obtained.

4) Subsequent hot isostatic pressing of the workpieces at a temperature of 1500-1800 ° C and a pressure of 100-200 MPa. Table 1 presents the possible color characteristics of a polycrystalline synthetic jewelry material made of transparent ceramic based on yttrium aluminum garnet doped with transition and / or rare-earth metal ions.

Table 2 presents examples of compositions of jewelry material made of transparent ceramic based on yttrium aluminum garnet doped with transition and / or rare-earth metal ions. Impurity ions provide different colors of the material, while different ions can produce the same color. So, in order to obtain green jewelry material, it is possible to introduce Cr, V, or Tm ions into the matrix of yttrium aluminum garnet.

Specific implementation example No. 1

To obtain a polycrystalline synthetic jewelry material from transparent ceramics based on yttrium aluminum garnet doped with neodymium ions, nanocrystalline yttrium aluminum garnet powder doped with neodymium ions prepared by the coprecipitation of hydroxocarbonates with a particle size of less than 200 nm and a specific surface of about 120 m ^{2 is} used as a raw material / g

Then, a heat treatment of the initial powder mixture is carried out, consisting of a nanopowder of aluminum nitride garnet doped with neodymium ions at a temperature of 300 ° C for 4 hours. After heat treatment, the powder mixture is ground in a planetary ball mill for 120 minutes to obtain a powder with a particle size of 30-100 nm. Then, the crushed powder mixture is subjected to hot uniaxial pressing at a temperature of 1450 ° C and a pressure of 200 MPa, followed by hot isostatic pressing at a temperature of 1700 ° C and a pressure of 200 MPa.

As a result, transparent pink ceramics based on yttrium aluminum garnet doped with neodymium ions can be obtained, having a Vickers microhardness of 1.29-1.35 MPa, a density equal to the density of a single crystal, and a transmittance in the visible region of 50-80%.

The microhardness meter ПМТ-3 is used to measure the microhardness of ceramic samples. The transmission spectra are recorded on spectrophotometers SF-20 in the range from 300 to 2500 nm and IKS-29 - from 2500 to 6000 nm (with an error of 1%). Density is determined by hydrostatic weighing.

Similarly to the described example, other samples of polycrystalline synthetic jewelry material based on yttrium aluminum garnet with different colors were obtained (see tables 1 and 2).

Table 3 shows the possible color characteristics of a polycrystalline synthetic jewelry material made of transparent ceramic based on aluminum-magnesium spinel alloyed with transition and / or rare-earth metal ions.

Table 4 presents examples of compositions of jewelry material made of transparent ceramics based on aluminum-magnesium spinel doped with transition and / or rare-earth metal ions. Impurity ions provide different colors of the material, while different ions can produce the same color. So, to obtain jewelry material of blue color, it is possible to introduce Co, or Ni, or Zn, or Ti ions into the matrix of aluminum-magnesium spinel. To obtain some colors, in particular orange, blue, it is necessary to simultaneously introduce two impurity ions.

Specific implementation example No. 2

To obtain a polycrystalline synthetic jewelry material from transparent ceramics based on aluminum magnesium spinel cobalt-doped, nanocrystalline aluminum-magnesium spinel powder doped with cobalt ions prepared by the method of coprecipitation of hydroxocarbonates with a particle size of less than 200 nm and a specific surface of about 120 m ^{2 is used} / g

Then carry out the heat treatment of the initial powder mixture consisting of nanopowder of aluminum-magnesium spinel doped with cobalt ions at a temperature of 300 ° C for 4 hours. After heat treatment, the powder mixture is ground in a planetary ball mill for 120 minutes to obtain a powder with a particle size of 30-100 nm. Then, the crushed powder mixture is subjected to hot uniaxial pressing at a temperature of 1550 ° C and a pressure of 35 MPa, followed by hot isostatic pressing at a temperature of 1800 ° C and a pressure of 200 MPa.

As a result, transparent blue ceramics based on aluminum-magnesium spinel doped with cobalt ions, having a Vickers microhardness of 1275-1675 MPa, a density equal to the density of a single crystal and a transmittance in the visible region of 50-80% can be obtained.

The microhardness meter ПМТ-3 is used to measure the microhardness of ceramic samples. The transmission spectra are recorded on spectrophotometers SF-20 in the range from 300 to 2500 nm and IKS-29 - from 2500 to 6000 nm (with an error of 1%). Density is determined by hydrostatic weighing.

Similarly to the described example, other samples of polycrystalline synthetic jewelry material based on aluminum-magnesium spinel with different colors were obtained (see tables 3 and 4).

The claimed group of inventions forms a single inventive concept: polycrystalline synthetic jewelry material from transparent ceramics based on yttrium aluminum garnet doped with transition and / or rare earth ions, and polycrystalline synthetic jewelry material from transparent ceramics based on aluminum-magnesium spinel doped with transition and / or rare metal ions , and methods for their preparation.

The resulting materials have all the basic characteristics shown to synthetic stones for the jewelry industry, as well as coloring and optical properties similar to natural analogues of stones.

The main advantages of the claimed technology for producing artificial gemstones from optical ceramics in comparison with the technology for growing single crystals are a wider color gamut of samples, the possibility of obtaining color effects due to the variable concentration of the activator or crystalline phases in the sample. In addition, the cost of products obtained by the claimed technology for producing jewelry materials based on ceramics is significantly lower than the cost of products obtained by growing crystals from synthetic single-crystal materials.

Claims (5)

1. Polycrystalline synthetic jewelry material obtained on the basis of transparent ceramics from yttrium aluminum garnet doped with transition and / or rare-earth metal ions (manganese, chromium, vanadium, thulium, nickel, cobalt, neodymium, erbium, terbium, europium, holmium, ytterbium) the amount of 0.001-10 mol. %, having a microhardness of from 1.29 to 1.35 MPa and transparency in the visible region of the spectrum in the range from 50 to 80%. 2. Polycrystalline synthetic jewelry material obtained on the basis of transparent ceramics from aluminum-magnesium spinel alloyed with transition and / or rare-earth metal ions (chromium, iron, manganese, cobalt, nickel, zinc, titanium) in an amount of 0.005-5 mol. %, having a microhardness from 1275 to 1675 MPa and transparency in the visible region of the spectrum in the range from 50 to 80%. 3. A method of obtaining a polycrystalline synthetic jewelry material based on transparent ceramics, including heat treatment of a powder mixture of the starting components, consisting of Y _3-x Me _x Al ₅ O ₁₂ , where Me is a metal dye, x = 0.00016-1.6 , or Mg _1-x Me _x Al ₂ O ₄ , where x = 0,00035-0.35, at a temperature of 200-400 ° C for 2-6 hours, additional grinding of the heat-treated powder mixture in a planetary ball mill for 1 -6 hours to obtain particles ranging in size from 30 nm to 100 nm, hot uniaxial pressing of powdered powdered with mixtures to obtain a pressed billet in the form of a disk with a density of at least 99% of theoretical density, subsequent hot isostatic pressing of the billets at a temperature of 1500-1800 ° C and a pressure of 100-200 MPa. 4. The method according to p. 3, in which upon receipt of a material based on transparent ceramics of aluminum yttrium garnet according to p. 1, the stage of hot uniaxial pressing of the crushed powder mixture Y _3-x Me _x Al ₅ O ₁₂ to obtain a pressed billet in the form of a disk with a density of> 99 % of the theoretical value is produced at a temperature of 1450-1750 ° C and a pressure of 35-200 MPa. 5. The method according to p. 3, in which upon receipt of a material based on transparent ceramics of aluminum-magnesium spinel according to p. 2, the stage of hot uniaxial pressing of a powdered mixture of Mg _1-x Me _x Al ₂ O ₄ to obtain a pressed billet in the form of a disk with a density of> 99 % of the theoretical value is produced at a temperature of 1400-1600 ° C and a pressure of 35-200 MPa.