Single crystal jewelry material based on a gadolinium - gallium garnet

 

(57) Abstract:

The invention relates to the field of artificial crystals and can be used in the jewelry industry in the manufacture of inlays in jewelry, simulated emerald, aquamarine, sapphire, amethyst. The aim of the invention is to obtain a single crystal jewelry material based on a gadolinium-gallium garnet GGG with color, smoothly changing from green to purple, a given brightness and achieving uniformity of dyeing by volume at a particular composition. Single crystal jewelry material based on GGG, corresponding to the formula Gd3Ga5O12contains as a coloring additives cobalt in the amount of 0.001-0.5 wt.% and zirconium in an amount of 0.001 to 0.6. per cent , with the total amount of additives does not exceed 0,8 wt. % . Crystals grown by Czochralski method, with a diameter of 35 mm and a mass of ~350 g . table 1.

The invention relates to the field of artificial crystals and can be used in the jewelry industry in the manufacture of inlays in jewelry, imitating emerald, aquamarine, sapphire, amethyst.

Known single-crystal jewelry material based on the im-gallium garnet. The material has a lilac color.

Known single-crystal jewelry material (prototype) based on a gadolinium-gallium garnet, corresponding to the formula Gd3Ga5O12containing as a coloring additives cobalt and vanadium in amounts of less than 0.5. % of each additive, and the total amount of cobalt and vanadium also does not exceed 0.5 wt.%. The most preferable content of additives - O < With + V < = 0.3 wt.%. The single crystals of the composition obtained by extrusion from the melt, crystallization, Verneuil and others and have a bluish-green color.

Growing single crystals of the composition of the most productive method, the Czochralski method, carried out by the inventors showed that the color is reproduced only in the upper part of the grown single crystal, when growing column and rassasyvanii cone, then while growing the cylindrical part, there is a change in color, the transparency disappears and appear brown area, which is connected, apparently, with the change in the composition of the melt due to the rapid evaporation from the melt of oxide of vanadium. This factor limits the ability of the General production of the em control the brightness of the coloring material in a specific color fade color change in a wide range of colours, as well as the achievements of blue and purple flowers, which are of interest for jewelry purposes for simulating, for example, sapphire, amethyst.

The aim of the invention is to obtain a single crystal jewelry material based on a gadolinium-gallium garnet colored, smoothly changing from green to purple, a given brightness, imitating emerald, aquamarine, sapphire, amethyst, and achieving uniformity of dyeing by volume at a particular composition.

This objective is achieved in that a single crystal jewelry material based on a gadolinium-gallium garnet, corresponding to the formula Gd3Ga5O12containing as a coloring additives cobalt in the amount of 0.001-0.5 wt.%, according to the invention, as a second additive contains zirconium in an amount of 0.001 to 0.6 wt.%, moreover, the total amount of additives does not exceed 0.8 wt.%.

The technical essence of the invention consists in the following.

When the separate introduction of the single crystal cobalt it replaces in the garnet-based trivalent element, therefore, is in the trivalent state. The cobalt is in the trivalent state in the gadolinium-gallium garnet has intenstine in gadolinium-gallium garnet tetravalent zirconium translates part of cobalt ions in the divalent state to compensate for the charge, that leads to a significant change in the absorption spectrum. A wide bandwidth from green to purple, the Increase in the concentration of cobalt in the gadolinium-gallium garnet shifts the bandwidth in the green region, while the increase in the content of zirconium shifts the bandwidth in the purple area. Thus, depending on the concentration of additives of cobalt and zirconium single crystal jewelry material based on a gadolinium-gallium garnet has a smoothly changing color in a wide range of color scale from green to purple, this also provides the ability to control brightness of staining in a wide range.

In addition, with the introduction of zirconium ions within the specified limits of concentration there is an increase of the coefficient of distribution of cobalt, which leads to uniform distribution of cobalt ions and zirconium by volume of the grown single crystal, and consequently the uniformity of the coloring material by volume at a particular composition.

With the introduction of additives zirconium in single crystal jewelry material based on a gadolinium-gallium garnet in the amount of less than 0.001 wt.% in the spectrum of PMN-green however, the uniformity of color is not achieved in the lower part grown on Choralschola single crystals observed the precipitation of secondary phases.

With the introduction of additives zirconium in single crystal jewelry material based on a gadolinium-gallium garnet in the amount of more than 0.6 wt.% is the cracking of the grown single crystals due to the strong distortion of the crystal lattice (zirconium ions with a radius of 0.75 takes the positions of the ions of gadolinium radius of 0.97 ).

If you increase the total amount of additives of cobalt and zirconium in a single crystal jewelry material based on a gadolinium-gallium garnet more than 0.8 wt.% solid solution during crystallization from the melt becomes non-equilibrium, observed precipitation of secondary phases.

Examples of specific performance.

As an initial charge in obtaining single crystals of gadolinium-gallium garnet with additions of cobalt and zirconium used a mixture of pre-calcined oxides: Gd2O3purity 99,995%, Ga2O5purity 99,999%, taken in the ratio 3: 5, the total mass of 800 g, and oxides COO and ZrO2taken in different quantities.

The mixture was napravlyali in licristal method of extrusion of the melt is oriented in a direction <111> the seed for Choralschola. The speed of pulling the single crystal 3-5 mm/h, the speed of rotation of the seed 10-30 rpm Cultivation was performed in a nitrogen atmosphere with the addition of 2% oxygen.

The grown single crystals of gadolinium-gallium garnet with different content of the additives of cobalt and zirconium. The diameter of the cylindrical part of the single crystal 35 mm; weight of about 350 g

Evaluation of staining of single crystals, its uniformity was performed on the spectra of optical transmittance in the visible region. Green color is associated with the absorption of ions of trivalent cobalt, purple - ions of divalent cobalt.

The composition of the grown single crystals and characterization of their quality are summarized in table. The table shows that, depending on the concentration of additives of cobalt and zirconium possible to obtain single crystals with color, smoothly changing from green to purple, a given brightness. The uniformity of color of the crystals is achieved at a certain ratio between the quantities introduced additives.

Thus, in comparison with the prototype, the invention allows to obtain a single crystal jewelry material based on a gadolinium-gallium garnet, corresponding to the formula Gd3

Single crystal JEWELRY MATERIAL BASED ON a GADOLINIUM-GALLIUM GARNET, corresponding to the formula Gd3Ga5O12containing as a coloring additives cobalt in the amount of 0.001 - 0.5 wt.%, characterized in that, in order to give the material color, smoothly changing from green to purple, a given brightness, imitating emerald, aquamarine, sapphire, amethyst, and achieve uniformity of staining volume at a specific part of the material as the second additive contains zirconium in an amount of 0.001 to 0.6 wt.%, and the total amount of additives does not exceed 0.8 wt.%.

 

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