DE2401106C3 - Process for the production of citrine crystals - Google Patents

Description

The invention relates to a process for the production of citrine crystals, a variant of the monocrystalline Quartz of yellow color of various tints. The citrine crystals mentioned are called Semiprecious stones are widely used in the jewelry industry.

There is a process of making citrine crystals by growing colorless quartz crystals underneath hydrothermal conditions in the temperature gradient method in a high pressure autoclave on quartz seed crystal plates, oriented parallel to the crystallographic Area of the pinacoid {0001} or to the named pinacoid area under one Angle in the range up to 20 ° inclined surfaces, from aqueous highly concentrated sodium carbonate solutions known using crystalline quartz as feed; the grown colorless quartz crystals if one is exposed to the action of ionizing radiation, which leads to the appearance of citrine color leads.

(See, for example, contribution by L. G. Gο rdienko and others in the anthology "Crystal Growth", 1967, Volume 7, pages 338 to 343, Verlag »Nauka«, in Russian).

Natural citrine crystals are extremely rare. An extraction takes place in deposits not held.

Disadvantages of the known method for producing citrine crystals are as follows:

1. Poor reproducibility of the process of growing colorless quartz crystals with potential Centers of citrine color as a result of the vagueness of the physico-chemical parameters this process (crystallization temperature, pressure in the autoclave and growth rate of the quartz crystals on the Seed crystal plates of the above orientations).

2. Insufficient color intensity for the practical use of citrine crystals, conditional by the specifics of the structure of the potential centers of citrine coloring in sodium carbonate solutions obtained crystals.

3. The crystals with potential centers of citrine color decrease after the action of the ionizing Radiation only has a light yellow color, which limits the range of jewelry made from these crystals.

4. Inhomogeneous distribution of the colored areas in the volume of the crystal, due to uninterrupted Heat destruction of the potential centers of citrine coloration in the one on the seed crystal plate grown crystalline material. After ionizing irradiation, it increases independently on the duration of the growth cycle and according to the size of the seed plate cultured layer only the outer zone of the crystal 1 to 4 mm thick the citrine color at. This largely eliminates the possibility of its appropriate practical use the citrine crystals obtained by the process mentioned.

5. When using highly concentrated sodium carbonate solutions, the process separates Cultivation of colorless quartz crystals from a precipitate of sodium silicates, which the lower Part of the autoclave contaminated and the discharge of the parts of the system where the input material is located from the autoclave is made much more difficult. The cleaning of the autoclave from the precipitate of sodium silicate is a very difficult task costly and unproductive operation.

The purpose of the present invention is to avoid the disadvantages mentioned.

The invention is based on the object of a method for the production of citrine crystals with to develop certain physicochemical parameters of the process of growing the crystals and thereby to ensure good reproducibility of the process mentioned, as well as a method to develop, which makes it possible to use intensely colored citrine crystals in the whole volume to obtain different shades and to avoid the formation of a silicate precipitate makes it difficult to discharge the input material from the autoclave.

This object is achieved in that when growing crystals under hydrothermal Conditions according to the temperature gradient method in a high pressure autoclave on quartz seed crystal plates, those parallel to the crystallographic surface of the pinacoids {0001} or to those mentioned above Pinacoid surface are oriented at an angle up to 20 ° inclined surfaces, from aqueous salt solutions using crystalline quartz

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According to the invention, metallic iron in an amount of 2 to 20 g / l solution and nitrites or nitrates of the alkali metals or potassium permanganate in an amount of 1 to 20 g / l solution and the growth of the crystals from aqueous Carrying out solutions of potassium carbonate with a concentration of 5 to 10 percent by weight at a crystallization temperature of 300 to 345 ° C, a pressure of 300 to 1500 kp / cm ² at a rate of 0.2 to 1 mm / 24 hours.

The cultivation conditions mentioned make it possible to obtain intensely and evenly colored citrine crystals of various shades (from greenish to orange), which are suitable for use in the jewelry industry as semi-precious grinding material. Under the described conditions, the centers of the citrine color arise immediately during the growth of the crystals through the incorporation of foreign ions of the trivalent iron into the crystal lattice, which are in the aqueous potassium carbonate solution (working solution) during the oxidation of the metallic iron through its interaction with the Form nitrites and nitrates of alkali metals or potassium permanganate. The mentioned centers of the citrine color are characterized by a relatively high thermal stability, which prevents their heat deterioration. If the process of crystal growth is carried out without the addition of compounds which ^{oxidize the iron to the Fe 3+ ion, the Fe 2+} ions can become embedded in the crystals, which leads to the production of greenish-brown quartz crystals.

The claimed process for the production of citrine crystals is characterized by simple apparatus Design, consisting of simple technological operations, avoiding the use of costly in scarce amount of available starting products and can be in high pressure autoclaves of different volumes reproduce safely.

According to the method according to the invention, the intensity and the shades of the citrine color in a targeted manner, taking into account the demands of consumers, within sufficiently broad limits the regulation of the growth rate of the crystals can be changed. So it grows with the increase Growth rate the color intensity and the citrine crystals take orange hue at. With the lowering of the growth rate, the color intensity decreases and the citrine crystals decrease greenish shade.

Alkali metal nitrites or nitrates, which have a sufficiently high solubility in the working solution of potassium carbonate, are particularly suitable additives that oxidize ^{the metallic iron in the working solution to the Fe 1+} ion required for the formation of centers of the citrine color in the crystals.

It is expedient to use lithium nitrites or lithium nitrates as nitrites or nitrates of the alkali metals. The lithium ions "clean" the solution of potassium carbonate from the undesired admixture of aluminum, which gets into the solution from the feed material, by binding the aluminum to sparingly soluble silicates of the eucryptite LiAISiO ₄ type, which causes the pyramids of the crystal surfaces to grow evenly . In the absence of lightium ions in the working solution, the aluminum admixture accumulates and the

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It is advisable to add metallic iron to the autoclave in an amount of 10 g / l of solution, nitrites or nitrates of the alkali metals or potassium permanganate in an amount of 5 g / l of solution before the crystals are grown, and the crystals are grown at a crystallization temperature of 335 ° C, a pressure of 1500 kp / cm ² at a speed of 0.5 to 0.6 mm / 24 hours. Carrying out the process at the stated temperature and the stated pressure ensures a high efficiency of the stated process (the growth rate of the crystals is high enough) and a high reproducibility of the same. At a higher growth rate, the color intensity of the citrine crystals exceeds the optimal limits for the practical use of the crystals. Jewelery made from richly colored citrine crystals absorb a lot of light and lose the »play of colors«. When the pressure and the temperature drop below the level mentioned, the citrine crystals decrepit due to stresses occurring at the interface between the seed crystal plate and the single crystal layer grown thereon, which results in a decrease in the yield of products. It also slows the growth rate of the crystals and consequently the efficiency of the process.

The method according to the invention for producing citrine crystals is carried out as follows.

A container is brought into the lower part of the high pressure autoclave, the dissolution chamber the input material, crystalline quartz. Single-crystalline or polycrystalline natural quartz, Synthetic quartz crystals or a mixture of synthetic and natural quartz crystals be used. Metallic iron is added to the feed material before it is placed in the autoclave in the form of tape or chip by distributing the iron evenly over the volume of the material to be used. After the container has been placed in the autoclave, it is installed above the container in the in Height direction of the autoclave middle part a transverse partition with openings, which the dissolution chamber from the top of the autoclave separating the growth chamber. Then you put in the Growth chamber a frame with attached quartz seed crystal plates, which are parallel to the crystallographic surface of the pinacoid {0001} or the surfaces inclined to the named pinacoid surface at an angle in the range of up to 20 ° are oriented. At the same time, seed crystal plates of various named orientations can be placed on the frame be attached. After the input material and the seed crystal plates have been introduced, the Autoclave an aqueous potassium carbonate solution (working solution) and then gives the addition of a oxidizing compound (alkali metal nitrite or alkali metal nitrate or potassium permanganate) too. The mentioned additives can also be added to the dissolution chamber of the autoclave (the container with the input material) before pouring the working solution into the

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Autoclaves are added. The degree of filling of the autoclave with the working solution is taken into account the achievement of the necessary crystallization temperature (in the range from 300 to 345 ° C) calculated from the given pressure in the autoclave.

After it has been introduced, the autoclave is hermetically sealed and the necessary cultivation conditions are created with the aid of electric heaters (the cultivation conditions are understood to mean the crystallization temperature, the pressure in the autoclave and the growth rate of the crystals). The pressure in the autoclave is created by the thermal expansion of the working solution. Since the process comes about under isochoric conditions to-^ ^5, the print size of the temperature in the autoclave is functionally dependent. The specified growth conditions are maintained in the autoclave for the entire duration of the crystallization process. The duration of the cycle (in 24 hours) is calculated using the formula τ = d / v , where d (in mm) is the specified thickness of the layer of crystalline citrine grown on the seed crystal plate and ν (in mm / 24 hours) is the specified The growth rate of the grown layer of the crystalline citrine on the seed crystal plate means the chosen orientation. After the end of the cultivation cycle, the electrical heating elements are switched off and the autoclave is naturally cooled to room temperature, opened and the frame with the cultivated citrine crystals is removed from it. The crystals are removed from the frame, washed with room temperature water, dried and sent to consumers.

In order to better understand the present invention, the following examples of preparation are given led by citrine crystals.

example 1

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The feed material, the single-crystalline synthetic quartz, the quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001}, an aqueous potassium carbonate solution with a concentration of 5 percent by weight, metallic iron in a quantity of 2 g / l solution and were brought into a high-pressure autoclave Lithium nitrite LiNO ₂ in an amount of 1 g / l solution. The growth of the citrine crystals was carried out at a crystallization temperature of 300 ° C and a pressure of 300 kgf / cm ² so at a rate of 0.2 mm / 24 hours.

The citrine crystals grown were bright yellow in color of high purity evenly over the whole Volume of crystals distributed. A part (-30%) of the citrine crystals contained cracks.

Example 2

The input material, natural polycrystalline quartz, quartz seed crystal plates, oriented parallel to the surfaces inclined to the crystallographic pinacoid surface {0001} at an angle of 10 °, an aqueous potassium carbonate solution with a concentration of 5 percent by weight, metallic iron, was placed in a high pressure toclave in a f> 5 amount of 5 g / l solution and lithium nitrate LiNO ₃ in an amount of 1 g / l solution. The growth of the citrine crystals was carried out at a crystallization temperature of 315 ° C and a pressure of 380 kgf / cm at a rate of 0.3 mm / 24 hours.

The citrine crystals grown had a golden yellow color of high purity, evenly over the whole Volume of the crystals distributed, and contained individual cracks.

Example 3

The feed material, single-crystal synthetic quartz, quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} at an angle, was placed in a high-pressure autoclave! of 18 "inclined surfaces, an aqueous potassium carbonate solution with a concentration of 10 percent by weight, metallic iron in an amount of 10 _{g / l solution and lithium nitrate LiNO 3} in an amount of 20 g / l solution. The citrine crystals were grown at a crystallization temperature of 335 ° C and a pressure of 1400 kp / cm ² at a speed of 0.5 mm / 24 hours.

The citrine crystals grown contained no cracks and had a vivid golden yellow color Purity, evenly distributed over the entire volume of the crystals.

Example 4

The feed material, natural single-crystalline quartz, quartz seed crystal plates, oriented parallel to the surfaces inclined to the crystallographic pinacoid surface {0001} at an angle of 20 °, an aqueous potassium carbonate solution with a concentration of 10 percent by weight, metallic iron in an amount of 15 g / l solution and potassium nitrite KNO ₂ in an amount of 5 g / l solution. The citrine crystals were grown at a crystallization temperature of 320 ° C. and a pressure of 400 kgf / cm ² at a speed of 0.4 mm / 24 hours.

The citrine crystals grown contained no cracks and were yellow in color, uniform distributed over the entire volume of the crystals.

Example 5

The feed material, the monocrystalline synthetic quartz, the quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} and parallel to the surfaces inclined to the named pinacoid surface at an angle of 18 °, an aqueous potassium carbonate solution with a concentration of 5, was placed in a high-pressure autoclave Percent by weight, metallic iron in an amount of 10 _{g / l solution and lithium nitrite LiNO 2} in an amount of 1 g / l solution. The cultivation of the cintricrystals was carried out at a crystallization temperature of 335 ° C. and a pressure of 1400 kgf / cm ² at a speed of 0.6 mm / 24 hours.

High quality citrine crystals were grown under the conditions mentioned, which have an intense have a golden yellow color.

Example 6

The feed, a mixture of monocrystalline synthetic materials, was placed in a high pressure autoclave and polycrystalline natural quartz,

Quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} and parallel to the surfaces inclined to said pinacoid surface at an angle of 18 °, an aqueous potassium carbonate solution with a concentration of 5 percent by weight, metallic iron in an amount of 20 g / l solution and Potassium nitrate KNO ₃ in an amount of 5 g / l solution. The citrine crystals were grown at a crystallization temperature of 320 ° C., a pressure of 400 kgf / cm ² at a speed of 0.4 mm / 24 hours.

The citrine crystals grown contained individual cracks and were yellow in color, uniformly distributed over the entire volume of the crystals.

Example 7

In a high-pressure autoclave, the input material, the single-crystal synthetic quartz, quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001}, an aqueous calcium carbonate solution with a concentration of 10 percent by weight, metallic iron in an amount of 12 g / l solution and sodium nitrite NaNO _{2 were brought} in an amount of 10 g / l of solution. The citrine crystals were grown at a crystallization temperature of 345 ° C. and a pressure of 1500 kgf / cm ² at a speed of 1 mm / 24 hours.

The citrine crystals grown had an insufficiently pure (opalescent) yellow color, the in the outer layer of the crystals was and were due to the uneven surface of the pinacoid and the presence of capillary channels in the outer layer 4 mm thick.

Example 8

The input material, monocrystalline synthetic quartz, the quartz seed crystal plates, oriented parallel to the crystalline pinacoid surface {0001}, an aqueous calcium carbonate solution with a concentration of 5 percent by weight, metallic iron in an amount of 20 g / l solution and sodium nitrate NaNO _{3 were placed in a high-pressure autoclave} in an amount of 10 g / l solution. The citrine crystals were grown at a crystallization temperature of 320 ° C. and a pressure of 1500 kgf / cm ^: at a speed of 1 mm / 24 hours.

The citrine crystals grown had an intense reddish-orange color and opalescent die Color was evenly distributed over the entire volume of the crystals. The crystals showed no cracks on.

Example 9

The feed material, the natural polycrystalline quartz, quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} and parallel to the surfaces inclined to the named pinacoid surface at an angle of 5 °, an aqueous potassium carbonate solution with a concentration of 10 percent by weight, was placed in a high-pressure autoclave , metallic iron in an amount of 10 g / l solution and potassium permanganate KMnO ₄ in an amount of 5 g / l solution. The citrine crystals were grown at a crystallization temperature of 335 ° C. and a pressure of 1200 kgf / cm ² at a speed of 0.6 mm / 24 hours.
The citrine crystals that were grown were colored golden yellow and contained no cracks. The color was evenly distributed over the entire volume of the crystals.

_t0 example 10

The feedstock, monocrystalline synthetic quartz, quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001}, an aqueous potassium carbonate solution with a concentration of 10 percent by weight, metallic iron in an amount of 10 g / l solution and lithium nitrite LiNO ₂ in an amount of 5 g / l solution. The citrine crystals were grown at a crystallization temperature of 345 ° C. and a pressure of 600 kgf / cm ² at a speed of 0.8 mm / 24 hours.

The citrine crystals grown had yellowish-orange color in the inner areas and pale yellow Paint in the outer area of 5 mm thick. In the outer area there were capillary cavities, which disturb the homogeneity of the citrine crystals.

Example 11

jo The feed material, natural polycrystalline quartz, quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001}, an aqueous potassium carbonate solution with a concentration of 7 percent by weight, metallic iron in an amount of 5 g / l solution and cesium nitrate were brought into a high-pressure autoclave CsNO, in an amount of 3 g / l solution. The growth of the citrine crystals was carried out at a crystallization temperature of 330 ° C and a pressure of 800 kgf / cm ² at a speed of 0.4 mm / 24 hours.

The citrine crystals grown were pale yellow in color, evenly over the entire volume of the Crystals distributed. The surface of the pinacoid is uneven.

Example 12

The charge, monocrystalline synthetic quartz, was placed in a high-pressure autoclave.

for example quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} and parallel to the surfaces inclined to said pinacoid surface at an angle of 18 °, an aqueous potassium carbonate solution with a concentration of 7 percent by weight, metallic iron in an amount of 10 g / l solution and lithium nitrite LiNO ₂ in an amount of 5 g / 1 solution. The citrine crystals were grown at a crystallization temperature of 335 ° C. and a pressure of

1500 kgf / cm ^{2 was carried out} at a speed of 0.5 mm / 24 hours.

The citrine crystals that were grown contained no cracks and had an intense yellow color orange shading. the

b5 crystals were uniform throughout the volume of the grown single crystal layer colored.

Claims (3)

Patent claims: 1. Process for the production of citrine crystals by growing crystals under hydrothermal conditions according to the temperature gradient process in a high pressure autoclave on quartz seed crystal plates, oriented parallel to the crystallographic pinacoid surface {0001} or to the surfaces inclined to the named pinacoid surface at an angle of up to 20 °, from aqueous Salt solutions using crystalline quartz as feed, characterized in that metallic iron in an amount of 2 to 20 g / l solution and nitrites or nitrates of the alkali metals or potassium permanganate in an amount of 1 to 20 g are added to the autoclave before the crystals are grown / l solution and the growth of the crystals from aqueous solutions of potassium carbide with a concentration of 5 to 10 percent by weight at a crystallization temperature of 300 to 345 ° C and a pressure of 300 to 1500 kp / cm ² at a rate of 0.2 to 1 mm / 24 hours. 2. The method according to claim 1, characterized in that the nitrites or nitrates Alkali metals lithium nitrites or lithium nitrates are used. 3. The method according to claim 1 or 2, characterized in that the autoclave is supplied with metallic iron in an amount of 10 g / l solution, nitrites or nitrates of the alkali metals or potassium perinanganate in an amount of 5 g / l solution before the crystals are grown and growing the crystals at a crystallization temperature of 335 ° C and a pressure of 1500 kgf / cm ² at a rate of 0.5 to 0.6 mm / 24 hours.