A method of growing a shaped crystals

 

(57) Abstract:

The invention relates to techniques for growing shaped crystals from the melt with variable cross-sectional shape. The essence of the proposed method lies in the fact that the persecution is produced on the seed plate around the perimeter of the tubular shaper with the formation of a hollow closed volume and pull out of the post of the melt at the end of the shaper, immersed in the crucible and the growth chamber. While the shaper is equipped with rethermalization acapillary hole, which is at the growth stage monolithic crystal is below the level of the melt. When moving to a hollow profile tubular cavity shaper reported through the opening indicated with the growth chamber by lowering the level of the melt in the crucible below ratemyserver openings, and at the transition from the hollow profile to monolithic stop communication between the cavity of the shaper and the growth chamber by raising the melt to total immersion razgermetiziruetsya holes in the melt.

The invention relates to techniques for growing shaped crystals from the melt with variable cross-sectional shape. P is the super new profiles crystals, which is essentially finished structural units of different instruments and devices.

The invention can be used for growing crystals of materials, melts them moisten the material used formers, in particular, ruby, sapphire, yttrium aluminium garnet eutectic composition of refractory oxides, lithium niobate, molybdates rare earth metals, etc.

There is a method of growing a shaped crystals with variable cross-section (variation method of forming) [1] including the persecution of the crystal with the creation of the meniscus of the melt between the seed crystal and shaper with capillary channels, the stretching and growth of the crystal. Moreover, the melt can flow either all capillary channels shaper, or their separate parts. The flow of the melt in the capillary channels to the working edges of the shaper or her termination ("on" or "off" part of the capillary channels) allows a controlled transition from one part of the profile to another.

The disadvantage of this method is that this method of growing it is impossible to obtain crystals, free of the authorized concentration of gaseous impurities, tasneema interfacial surface, adjacent to the plots of the crystallization front, under which components of the flow velocity of the melt is minimal. Area with a minimum speed of radial currents are formed by the meeting of the streams of melt spreading on the end face of the shaper. These areas are the places most likely nucleation and capture gas inclusions [2]

Also known is a method of obtaining crystals adopted for the prototype [3] in which the persecution is produced on the surface of solid bare plate simultaneously around the perimeter of the tubular shaper for the formation of a closed volume inside it, pre-grown hollow crystal, creating a differential between the pressure in the growth chamber and the pressure in the closed volume inside the hollow crystal to collapse it and grow a monolithic crystal.

The main disadvantage of this method is the impossibility of regular and controlled changes of the cross section of the grown crystal (transition from monolithic crystal to a hollow and back).

The technical result achieved by the present invention, consists in the possibility of growing crystals with regular and controlled change in the soba is that persecution is produced on the seed plate around the perimeter of the tubular shaper with the formation of a hollow zamknutogo and pull out of the post of the melt at the end of the shaper, immersed in the crucible and the growth chamber. While the shaper is equipped with rethermalization acapillary hole, which is at the growth stage monolithic crystal is below the level of the melt. When moving to a hollow profile tubular cavity shaper through the hole with the growth chamber by lowering the level of the melt in the crucible below razgermetiziruetsya openings, and at the transition from the hollow profile to monolithic stop communication between the cavity of the shaper and the growth chamber by raising the melt to total immersion razgermetiziruetsya holes in the melt.

Supply shaper rethermalization hole allows you to tell the tubular cavity shaper with the growth chamber, which is the condition for the growth of a hollow crystal required length, because there is no lifting of the melt in the Central acapillary channel. During the transition to the monolithic crystal razgermetiziruetsya hole palmore and pressure in the closed volume. Further pulling causes the melt up to the end of the shaper on acapillary channel, collapses with the melt flowing through the capillary shaper and begins to crystallizability throughout the volume, which leads to growth of a monolithic crystal. The quality of this crystal is characterized by the absence of gas bubbles in the bulk of its monolithic part, due to the exclusion of opposing streams of melt flow (the main part of the melt is of Central neipirskogo channel to the periphery), and a decrease in the number of vklyucheniyami shaper and defects associated with contact with the shaper.

The technical essence of the method is illustrated with specific examples of its implementation.

Example 1.

Grown sapphire crucibles external diameter of 25 and 35 mm with wall thickness of 1,5 and 2 mm, respectively. The cultivation was carried out in argon atmosphere, the pressure in the chamber during growth was 0.3 ATM). For cultivation was used molybdenum formers with capillary and acapillary channels. The length of the formers was 50 mm, the middle length was razgermetiziruetsya a hole diameter of 6 mm Gladiolen her. The persecution was carried out by plate-seed the entire working surface of the shaper. To obtain the hollow part of the crucible melt level in a molybdenum crucible is below razgermetiziruetsya holes. The melt in this case comes only through the capillary channels - growing tube. For sealing pipe (for forming the bottom part of the sapphire crucible) molybdenum crucible with the melt coming up until razgermetiziruetsya hole will not be fully immersed in the melt. Due to the pressure difference in the chamber and in the inner acapillary part of the shaper on acapillary channel begins to rise melt with subsequent crystallization in the upper edge area of the shaper is growing monolithic piece of crystal. Subsequent lowering of the molybdenum crucible with the melt when the melt level in the crucible is again below razgermetiziruetsya holes, melt isnegativezero channel is poured through the sealing hole, melt again comes only through the capillary channels grows hollow part of the crystal. Thus, it is possible to carry out several sapac in one process. The claimed method were obtained sapphire crucibles in length from 40 to 200 mm (ptx2">

Grown single-crystal crucibles made of lithium niobate with a diameter of 12 mm with wall thickness of 1,5-2 mm of platinum shaper. The cultivation was carried out in air. For persecution used plates of lithium niobate, a plane lying perpendicular to the axis C. the Soldering and unsoldering of the crucibles was carried out analogously to example 1. Were grown crucibles made of lithium niobate 40-60 mm in length (two crucible for one growth process) free of gas inclusions in their bottom part.

Example 3.

Grown single-crystal crucibles made of gadolinium molybdate, 10 mm in diameter with a wall thickness of 1.5 mm of platinum shaper. The cultivation was carried out in air. For persecution were used plate of gadolinium molybdate, a plane lying perpendicular to the axis C. the Soldering and unsoldering of the crucibles was carried out analogously to example 1. Were grown crucibles made of gadolinium molybdate length of 40 mm, free of gas inclusions in their bottom part.

1 is a Method of growing a shaped crystals, including persecution around the perimeter of the tubular shaper with the formation of a hollow closed volume under the apron seed and growing a hollow crystal, is Mooresville perform razgermetiziruetsya acapillary hole and during the transition to growth in the hollow section of the tubular cavity shaper reported through the opening indicated with the growth chamber by lowering the level of the melt below razgermetiziruetsya holes, and during the transition to growth monolithic profile stop communication between the cavity of the shaper and the growth chamber by raising the melt to total immersion razgermetiziruetsya holes in the melt.

 

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