Sapphire Grow Method - Micro-Pulling And Shoulder Expanding at Cooled Center (SAPMAC)

Micro-pulling and shoulder expanding at cooled center is a sapphire growth method, which is also called micro-pulling rotation Kyropoulos. The is an improved method based on Kyropoulos Method and Pulling Method by Institute of Composite Structures from the Harbin Institute of Technology. It is used to grow large size crystal. Crystal growing system includes control system, vacuum system, heating body, cooling system and thermal protection systems. The following a picture, which is a schematic shoulder cold heart to put the system trace Czochralski method, SAPMAC grown single crystal, the outlook is usually pear-shaped, crystal diameter crucible can grow to more than the inner diameter of the small size of 10 ~ 30mm. The seed is processed into split shape, use seed clips at the bottom of the heat exchanger. Rotating and pulling the heat exchanger can be accomplished seed fixed, crystals, and the exchange interaction between the heat exchanger, crystal and melt.

Cold Heart put the shoulder when trace Czochralski growth of sapphire crystals, usually the entire crystal growth process can be divided into four control phases, namely seeding, put the shoulder, and other tracks, annealing and cooling phases. Seeding stage and put the shoulder is the use of adjusting heat exchanger cooling capacity, appropriate with a certain reduction in heating temperature (heating system can provide the crucible outer wall temperature) way to achieve the crystal and put the shoulder necking control. At this time the crystal growth rate and temperature gradient interface projecting large, which is conducive to the use of larger discharge shoulders, reducing the distance to put the shoulder to prevent flipping interface, while capable of dislocation within the seed crystal defects such as the original fast from Crystals spread to the crystal surface, effectively reducing defects within the crystal content. Large temperature gradient also can increase the interface crystal growth driving force, increase the stability of the interface. Until crystals grow to the desired diameter size (cold shoulder put heart trace Czochralski crystal diameter can grow from the inner wall of the crucible 1 ~ 3cm), crystals begin Equal grow into other tracks stage. With grown crystal size, heat exchanger efficiency of crystal growth decreases rapidly, so the crystal enters Once diameter growth stage, mainly by reducing the heating temperature(Crucible outer wall temperature of the heating system can provide) to achieve crystal growth.

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Sapphire Grow Method-Vertical Horizontal Gradient Freezing (VHGF)

Vertical horizontal Gradient freezing method is shorted to VHGF method, which is a method used for producing large quantity sapphire crystal. This technique is a vertical temperature gradient cooling system based on the law, and the use of VGF grown GaAs crystal rods, low potential density can reach high quality crystal rods. VGF is divided based on the law, the combination of the horizontal temperature gradient cooling process, this way, can long grain size (diameter and height) and long-grain shape is relatively unrestricted.



Chunks of polycrystalline, produced by horizontal synthesis, are placed in a crucible with a seed crystal of the required orientation. The crucible is then placed vertically in a furnace and a temperature gradient is moved up the length of the crystal (away from the seed).

Single crystal growth propagates from the seed crystal and, because the crystal forms in the shape of the crucible, diameter control of the ingot is relatively simple.

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Sapphire Growth Method- Vertical Gradient Freeze Method (VGF)

Vertical gradient freeze method is similar to the level of zone melting, mainly in the way of moving the crucible, so that a temperature gradient within the molten metal, and then began to grow crystals. This method used by the heater is divided into two parts, the top of the furnace body heater temperature is higher, lower temperature below the temperature difference generated by the heater caused the temperature gradients, thus growing crystals. Because of the growth process, the temperature of the heater is constant, and the heater from the solid-liquid interface of the crystal growth when it is fixed, in which case you must make Bridgman, make molten metal through the solid-liquid interface, the use of VGF way, it solidified molten metal normal form a single crystal. Its growth principle is as the picture showing.

The features of VGF method are as following:
1) The shape of the crystals may vary depending on the shape of a crucible for growing profiled crystals;
2) Plusing the seed crystal growth orientation can also be natural nucleation, based on the principles of geometry out of the crystal growth;
3) This method can be closed or semi-closed crucible to grow. Prevent evaporation melt dopant, resulting in compositional deviation and doping concentration, and can be on the surrounding environment pollution and hazardous substances;
4) It is suitable for large size, growing large number of crystals. A furnace can grow a few or dozens of different root, different sizes of crystals.
5) Operation process is relatively simple, easy to implement procedures and automation. VGF main drawbacks as follows:

Processes of VGF:
1) The whole process of crystal growth is carried out inside the crucible, which is not easy to observe the growth because of the invisible material of tungsten. If the crucible is not made of tungsten, mo, or other metals, but glass, then it would be different.
2) Different crystals require specify physical and chemical properties of the crucible. Especially in matching the crucible and the thermal expansion coefficient of crystalline material to the right, while unsuitable for crystal growth of crystalline material volume expansion.
3) Tungsten crucible will stress and create parasitic crystal nucleation crystal during the sapphire growth. Therefore, the requirement of inner surface finish for crucible is very high.
4) When using Vertical Gradient Freeze method to grow sapphire crystal, the going down of crucible is not rotating, so that the quality of crystal is not better than the one grows out by grow out by Czochralski method.

If there is any other question refer to tungsten crucible for sapphire growth furnace, please feel free to contact us through the following methods:
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Sapphire Growth Method- Temperature Gradient Technique (TGT)

Temperaturegradient technique, shorted to TGT, is one of sapphire growth methods, invented by Zhou Yongzong and the staff of Shanghai Institute of Optics and Fine Mechanics in China. This method applied orientation seed to grow sapphire. Physical process of TGT: 

Climatology
On a global and annual basis, the dynamics of the atmosphere (and the oceans) can be understood as attempting to reduce the large difference of temperature between the poles and the equator by redistributing warm and cold air and water, known as Earth's heat engine.

Meteorology
Differences in air temperature between different locations are critical in weather forecasting and climate. The absorption of solar light at or near the planetary surface increases the temperature gradient and may result in convection (a major process of cloud formation, often associated with precipitation). Meteorological fronts are regions where the horizontal temperature gradient may reach relatively high values, as these are boundaries between air masses with rather distinct properties.

Clearly, the temperature gradient may change substantially in time, as a result of diurnal or seasonal heating and cooling for instance. This most likely happens during an inversion. For instance, during the day the temperature at ground level may be cold while it's warmer up in the atmosphere. As the day shifts over to night the temperature might drop rapidly while at other places on the land stay warmer or cooler at the same elevation. This happens on the West Coast of the United States sometimes due to geography.

Weathering
Expansion and contraction of rock, caused by temperature changes during a wildfire, through thermal stress weathering, may result in thermal shock and subsequent structure failure.

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Tungsten Heat Shield Price on Dec. 19, 2017

Tungsten heatshield price is 370.00USD/PC on Dec. 19, 2017, EXW, Xiamen, China. This quotation is for sapphire growth furnace industry, which is not used separately. The quotation is for one piece, and we can produce and install the whole set if you can provide us your idea or drawings.

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Leybold Tungsten Filament Price on Dec.19, 2017

Leybold tungsten filament price is 8.00USD/PC on Sep. 30, 2017, EXW, Xiamen, China. This kind of filament is used in Leybold machine, with a diameter of 0.6mm and length of 30.2mm.

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Tungsten Granule Price on Dec. 23, 2017

Tungsten granule price is 67.20USD/KG on Sep. 30, 2017, EXW, Xiamen, China. Tungsten granule is mainly used for carbon and sulfur analysis and the most widely used grain size is 20~40mesh.

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Cerium Tungsten Electrode Price on Dec. 19, 2017

Cerium tungsten electrode price is 0.877USD/PC on Dec. 19, 2017, EXW, Xiamen, China. The content of CeO2 is 1.7~2.2%, its tip color is grey. The international standard of tungsten electrode is ISO6848.

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