PL183471B1 - Apparatus for monocrystallising oxide materials in particular neodymium gallate, by use of czochralski process - Google Patents

Abstract

Device for monocrystallization of oxide materials by the Czochralski method, especially ga "neodymium lattice, containing situated in the tube a ceramic housing with a heating system and detachable a cover placed on it, coaxially melted crucible placed detachably in the housing input material and two additional heaters upper and lower and passing through the center located in the housing cover and upper bottom auxiliary heater holes vertical ceramic tube, coupled to the rotary extraction mechanism, to which a single crystal seed is attached, characterized in that the main crucible (4) with the melt charge material (5) is placed directly coaxial on the lower reheating crucible (6) filled with insulating material, preferably a ceramic material, and on the essential crucible (4) is directly based coaxial upper holding crucible (7) thick wall corresponding to the thickness of the crucible main (4), while the heating system (8), preferably in the form of an induction coil, includes the main crucible (4) and completely within its reach or a partially lower and / or upper holding crucible (6, 7).

Description

The subject of the invention is a device for monocrystallization of oxide materials by the Czochralski method, especially of neodymium gallate.

Known devices for monocrystallization by the Czochralski method consist of a monocrystallization chamber with a thermal system, coupled with a rotary extraction mechanism. Depending on the material to be pulled out and the crystal diameter, different solutions of the thermal system are used.

The main problem is to create an appropriate temperature gradient, both axial and radial, in the thermal system.

In the monocrystallization device known from East German Patent Specification No. 215340, the thermal system comprises a heating crucible suspended above the crucible with the charge material, the wall thickness of which is considerably smaller than that of the crucible with the charge material. Moreover, under the crucible with charge material there is an additional heater for the bottom of the crucible, separated from it by an insulating ceramic plate. However, in the case of, for example, neodymium gallate in such a thermal system, unfavorable temperature gradients arise, as a result of which stresses and twins and related structural defects occurred in the obtained crystals.

The neodymium gallate monocrystallization device known from R. Vecker et al., Journal of Crystal Growth, 137 (1994) 278-282, comprises a crucible with a charge material placed directly in the ceramic. Crystals up to 1.5 inch in diameter were obtained on this equipment.

A similar solution was used in the device known from PReiche et al., Crystal Res. Technol., 20, 6, 845-849 (1985).

In the device known from H. Matthes, Journal of Crystal Growth, 15 (1972) 157-158, a cone-shaped booster with a static booster ring was used to ensure a homogeneous temperature distribution in the area of the drawn crystal.

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In an apparatus for monocrystallization of oxide materials, known from B. Cockayne et al., Journal of Crystal Growth, 15 (1972) 167-170, selective cooling of the crucible bottom by gas dosing was used to control the crystal diameter. However, such a device can only be used for small crystal diameters of less than 1 inch.

The thermal system of the working chamber has a decisive influence on the temperature gradients and the shape of the crystallization front, which in turn determine the quality of the obtained crystal.

In the oxide crystals, especially neodymium gallate, obtained in devices known to date, stresses and structural defects occurred due to the formation of unfavorable temperature gradients and underheating of the bottom of the crucible with the charge material.

The object of the invention is to provide such a device structure which will overcome the disadvantages of the previously known devices for monocrystallization of oxide materials, especially neodymium gallate.

The essence of the invention is that the main crucible with the molten charge material is placed directly coaxially on the lower heating crucible filled with insulating material, and the main crucible is directly coaxially supported by the upper heating crucible, turned upside down, with a wall thickness corresponding to the thickness of the crucible wall. the main crucible, the heating system extending over the main crucible and wholly or partially the lower and / or the upper holding-up crucible.

The device according to the invention is characterized in that it has a ceramic housing with a heating system, preferably in the form of an induction coil and with a cover detachably placed thereon, placed in a tube, preferably a quartz, with a cover, coaxially located, detachably in the housing, with the molten batch material and passing along the axis through a vertical hole, centrally located in the housing cover, a ceramic tube coupled to a rotating mechanical drawing system, to which a single crystal seed is attached. The main melt crucible is placed directly coaxially on the bottom reheating crucible filled with insulating material, preferably ceramic. The main crucible rests directly on the coaxial top of the heating crucible, turned upside down, with a wall thickness corresponding to that of the main crucible, with a centrally located hole in the bottom for a vertical ceramic tube. The heating system covers the main crucible and the complete or partial lower and / or upper holding crucible.

Preferably, the lower holding crucible has a wall thickness corresponding to that of the main crucible.

The device according to the invention makes it possible to obtain the optimal temperature in the main crucible - heating crucible system, which allows to obtain a favorable temperature gradient, both radial and axial, in the area of the drawn crystal. The device according to the invention also makes it possible to obtain a homogeneous temperature field in the space surrounding the crystal, which is very important for cooling the crystal after its separation from the liquid.

The device according to the invention makes it possible to obtain oxide single crystals, especially neodymium gallate, also of larger diameter than before, of the required structural quality, without twins.

The subject of the invention in an exemplary embodiment is shown in the drawing in an axial section.

The device shown in the drawing has a housing 2 made of alumina ceramics placed in a quartz tube 1 with a lid 3 detachably placed thereon. In the housing 2 there is a basic iridium crucible 4 with a melt batch 5 located coaxially coaxially on the lower iridium reheating crucible 6. filled with ceramic material. The wall of the holding crucible 6 has a thickness corresponding to the thickness of the main crucible 4. On the main crucible 4 is supported directly coaxially upside down iridium top holding crucible 7 with a wall thickness corresponding to the thickness of the primary crucible 4.

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Outside the casing 2 there is a heating system 8 in the form of an induction coil, which covers the main crucible 4 and both additional heating crucibles 6 and 7.

A vertical ceramic tube 9, coupled to a rotary extraction mechanism, not shown in the drawing, passes through the holes centrally located in the cover 3 and in the bottom of the upper heating crucible 7. A single crystal nucleus of a gallate of neodymium 10 is attached to the tube 9.

The operation of the device shown in the drawing is based on the fact that the nucleus of a single crystal of neodymium gallate 10, attached to the ceramic tube 9, touches the molten charge material 5 in the iridium crucible 4. Under certain process parameters, monocrystallization takes place by attaching particles of the molten material 5 to the nucleus 10.

In the area of the drawn crystal, due to the maintenance of the optimum temperature in the main crucible 4 - the heating crucibles 6 and 7, an advantageous radial axial temperature gradient is obtained. After the crystal reaches its assumed dimensions - inches in diameter - it is separated from the liquid and cooled down. When the crystal is cooled, a homogeneous temperature field is obtained in the space surrounding the crystal.

Publishing Department of the UP RP. Circulation of 50 copies

Price PLN 2.00.

Claims (2)

Patent claims 1. A device for monocrystallization of oxide materials by the Czochralski method, especially neodymium gallate, containing a ceramic casing located in the pipe with a heating system and a cover detachably placed on it, a crucible with melt charge material, coaxially detachably placed in the casing, and two upper and lower additional heaters, and passing through the center holes located in the housing cover and the bottom of the upper additional heat, a vertical ceramic tube coupled with a rotary extraction mechanism, to which a single crystal seed is attached, characterized in that the main crucible (4) with the molten charge material (5) is placed directly coaxially on the lower reheating crucible (6) filled with insulating material, preferably ceramic, and the main crucible (4) is supported directly by the coaxial upper reheating crucible (7) with a wall thickness corresponding to the wall thickness of the main crucible (4), the heating system (8), preferably in as an induction coil, it covers the main crucible (4) and completely or partially the lower and / or the upper heating crucible (6, 7). 2. The device according to claim The method of claim 1, characterized in that the lower re-heating crucible (6) has a wall thickness corresponding to that of the primary crucible (4).