Method of preparation of optically transparent single crystals of terbium-gallium garnet

FIELD: technological process.

SUBSTANCE: invention is related to growing of garnets single crystals and may be used in laser equipment, magnet microelectronics (semi-conductors, ferroelectrics) and for jewelry purposes. Single crystals of terbium-gallium garnet are prepared by Chochralski method by means of melting primary stock, which includes clarifying calcium-containing additive, and further growing of single crystal from melt to primer. As primary stock mixture of terbium and gallium oxides is used, as calcium containing additive - calcium oxide or carbonate, and after growing crystal is annealed in atmosphere of hydrogen at temperature of 850-950°C for around 5 hours until orange paint disappears.

EFFECT: allows to prepare optically transparent homogeneous crystals.

2 ex

 

The invention relates to single crystal growth and can be used for growing single crystals of garnet, more specifically of single crystals of the terbium-gallium garnet, used, for example, in laser technology, magnetic microelectronics, for jewelry purposes.

From the application of the Russian Federation No. 94008750, priority 27.04.1996 known colored crystals, in particular, colored crystals of a terbium-gallium garnet. Colored crystals with garnet structure was grown by the Czochralski method in iridium or platinum crucible (if the composition of garnet is dominated by niobium and calcium). For single crystals on the basis of calcium-niobium-gallium garnet optimal are the following growth conditions: speed drawing of 2-5 mm/h, the speed of 60-80 rpm, the flow rate of oxygen through the reaction volume of 0.5-2 l/min, the ratio of the diameter of the crystal to the diameter of the crucible is not more than 0.6. The grown crystals had a diameter of 80 mm, and from the melt passed into the crystal up to 75 substance.

The grown crystals were subjected to one of the types of treatment: irradiated by x-rays; annealed in vacuum at temperatures up to 800-C for 0.5-10 h, followed by lowering the temperature at a speed of 500 K/h; annealed in an inert atmosphere for 0.5 to 40 hours at a temperature of not higher than K, annealed in the spirit at temperatures up to C.

Known for the single crystals obtained using the introduction of colored crystal additional impurities Me, valency of ions which is different from the valence of ions of coloring impurities M and/or matrix of single crystal And that leads to a number of physical effects that affect the color of the crystal.

Colored crystals were obtained of various known methods, for example by the method Bagdasarova, by the Czochralski method. Obtaining crystals of a terbium-gallium garnet in published application are not described.

From the application of the Russian Federation No. 94008773, priority 27.04.1996 known colorless synthetic single crystal, including with garnet structure, in particular, the matrix of the single crystal can be made on the basis of the terbium-gallium garnet (matrix) and optionally contain as enlightening impurities neodymium, nicely and/or cobalt, and the content of ar impurity ranges from 10-8up to 10-2wt.% and may in addition optionally contain additional enlightening impurities (calcium, strontium and/or magnesium), and the content of the additional enlightening impurities ranges from 10-8up to 10-2wt.%.

Colorless crystals were obtained of various known methods, in particular by the method Bagdasarova, as well as the Czochralski method.

That is, in particular, colorless crystals with garnet structure was grown by the Czochralski method in iridium or platinum crucible (if the composition of garnet is dominated by niobium and calcium). For single crystals on the basis of calcium-niobium-gallium garnet optimal are the following growth conditions: speed drawing of 2-5 mm/h, the speed of 60-80 rpm, the flow rate of oxygen through the reaction volume of 0.5-2 l/min, the ratio of the diameter of the crystal to the diameter of the crucible is not more than 0.6. The grown crystals had a diameter of 80 mm, and from the melt passed into the crystal up to 75 substance.

Thus was obtained a clear, colorless single crystal on the basis of calcium-niobium-gallium garnet with the following content of components (in wt.): neodymium 0,002; is 0.0002 Nickel; cobalt 0,0007.

Examples to obtain single crystals on the basis of the terbium-gallium garnet in the well-known application for the present invention are absent.

The technical objective of the claimed invention to provide optically transparent single crystals of the terbium-gallium garnet (GTG) with a colorless color and high optical transparency with absorption coefficient of 0.5×10-3cm-1for use in laser technology.

The goal of the project is achieved by the method for obtaining optically transparent single crystals of the terbium-gallium g is Anata by the Czochralski method by fusion of the original charge, includes enlightening calcium Supplement and growing a single crystal from the melt on a seed crystal, and, according to the invention, as the original mixture, a mixture of oxide of terbium and gallium, as calcium maintenanced additive oxide or calcium carbonate, and after growing exercise its annealing in hydrogen atmosphere at 850-950°C for about 5 hours until the disappearance of the orange color.

Calcium oxide (Cao) or calcium carbonate (caso3) is injected into the melt in an amount of from 0.1 to 1.0 g once or twice before growing crystals on the amount of charge equal to 4-8 kg

Below is a specific example of the method, illustrating the invention, but not limiting it.

Example 1. An optically transparent single crystals of the terbium-gallium garnet (GTG) grown by the Czochralski method, for example, at the "SKIF-3" or the "SKIF-4". Grantourismo components (matrix) pre-dried (at a temperature of 800-1000°, for example) is weighed on an analytical balance, stirred until the formation of homogeneous mixture.

Typical approximate composition of the mixture may be such (wt.%):

Gallium oxide - 45,523

The oxide terbium - 54,477

From the mixture can be pressed tablets. The mixture (the mixture) is placed in a crucible (iridium or platinum), is melted, add calcium d is the additive (calcium Oxide (Cao) or calcium carbonate (caso 3in the molten mixture.

If you add calcium oxide (Cao), then it is added in an amount of 0.1 g in the composition of gallium oxide 45,523 wt.%, the oxide terbium 54,477 wt.%. If you add calcium carbonate (caso3), then it is added in an amount up to 1 g in the composition of gallium oxide 45,523 wt.%; the oxide terbium 54,477 wt%.

Next pull oriented crystals from the melt (the pulling of crystals on the oriented seed). The grown single crystal with the addition of calcium oxide (Cao) or calcium carbonate (caso3had an orange color and the absorption band in the wavelength range 400-659 nm. Next, carry out the annealing of the crystals for 5 hours in an atmosphere of hydrogen at 900°C. After annealing the crystal becomes colorless and the absorption band disappears. Are optically transparent single crystals.

Supplementation (calcium oxide (Cao) or calcium carbonate (caso3) prevent screw grow crystals. Their influence on the technical result (which, as stated above, is to obtain optically transparent single crystals of the terbium-gallium garnet (:) with a colorless color and high optical transparency with absorption coefficient of 0.5×10-3cm-1and for applications in laser technology) is to stabilize the process of growing and obstructing spiral growth of crystals.

Ed is Leah from the obtained single crystals - this is, for example, cylindrical elements, in particular, with a diameter of 20 mm and a length of 20-40 mm, or elements having the shape of a parallelepiped, for example, 3×10×20 mm, used for the manufacture of Faraday rotators.

The basic requirement for quality of the Faraday rotators is the optical homogeneity of the crystals and the magnitude of the absorption coefficient, which should be 30-40 dB and 0.5×10-3cm-1respectively.

Example 2. Get jewelry material based on optically transparent single crystals of the terbium-gallium garnet obtained by the Czochralski method similar to example 1, except that the annealing is subjected to receive jewelry (in the form of stones, for example) at 850°C in an atmosphere of hydrogen in the course of 4.8 hours.

When obtaining crystals of a terbium-gallium garnet claimed process using the following optimal growth conditions:

- speed drawing - 2-7 mm/h;

the speed of rotation of the crucible - 2-10 rpm;

the diameter of the seed is from 2 mm to 8 mm

The crystal growth is carried out in an inert atmosphere (e.g. under nitrogen atmosphere) with the addition of oxygen.

The grown crystals have a diameter of 80 mm, weight (mass) - 4-8 kg, the growth of crystals is 20-40 hours, the density of crystals ≈7.2 g/cm3.

A method of obtaining optically transparent monocrystalline-gallium garnet by the Czochralski method by fusion of the original charge, includes enlightening calcium Supplement and growing a single crystal from the melt on a seed crystal, characterized in that as the initial mixture, a mixture of oxide of terbium and gallium, as calcium maintenanced additive oxide or calcium carbonate, and after growing exercise its annealing in hydrogen atmosphere at 850-950°C for about 5 h until the disappearance of the orange color.



 

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2 ex

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