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Laboratory Crystal Growing Unit

We design and build laboratory units for three process methods to grow crystals from the melt:

• TAMMANN-STOEBER method (crystal growing in a stationary crucible);
• BRIDGEMAN method (the crucible is moved in the temperature field);
• Vertical zone melting;

All three methods use crucibles (diameters 12 to 24 mm). The maximum temperatures are
1750 °C. Various gases and vacuum can be used.

Accessories

• Pointed crucibles made of alumina ceramics, available from stock;
• Other crucible materials, e.g. yttria or aluminum nitride ceramics, on request;

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Examples

Crystal growing unit LORA 1700-40-600-1-vertical
BRIDGEMAN method
(Operation Manual (German) LORA furnace with a step motor AU03-0-064)

• Tmax: 1700 °C;
• Max. continuous working temperature 1650 °C
• Heating element = working tube made of Al₂0₃ (C799), with Mo heating wire directly wound around;
• Heated space: L = 600 mm (heating zone 450 mm), ID = 40 mm;
• Number of heating zones: 1 zone;


• With a step motor driven, movable crucible flange that is connected by a bellows to the working tube;
• Connections for gas inlet;
• 2 thermocouples (2 x type B, one is placed in the working tube top; the second is movable, thus always being at the height of the sample).

The crucial point of the Bridgeman method is to move the crystals out of the melt at an extremely low speed and vibration-free. The laboratory units enable up/down speeds of 0.1 to 20 mm/h.

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Crystal growing unit LORA/i 1800-32-800-1-vertical TAMMANN method

(User manual (German) Crystal growing unit AU07-0-065)

• Tmax: 1750 °C;
• Max. continuous working temperature 1500 °C;
• Tubular heating element made of Al₂O₃ concrete, with the Mo heating wire fixed to its inner surface;
• Working space: L = 600 mm (heating zone: 430 mm), ID = 43 mm;
• Number of heating zones: 1 zone;
• Working tube made of Al₂O₃ (C799), L = 800 mm, ID = 38 mm;
• gas- and vacuum-tight end flanges;
• Connections for gas inlet;
• Evacuation possible with a rotary vane pump;

As for the TAMMANN method, the crucible is placed in a steep temperature gradient of up to 12 K/mm. The temperature is reduced very slowly by some K/min, and very evenly due to the control electronics.

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Crystal growing unit LORA 1550-32-900-1-vertical with protective gas/vacuum atmosphere Vertical zone melting
(AU07-0-050)

• Tmax: 1550 °C;
• Max. continuous working temperature 1500 °C;
• Heating element = Al2O3 (С799)working tube, with Mo wire directly wound around the tube;
• Heated space: L = 900 mm (heated zone: 500 mm), ID = 32 mm;
• Maximum temperature gradient at the transition between from the heater to the point of open radiaton: ca. 300 K/cm;
• Number of heating zones: 1 zone;
• Housing tube made of quartz: L = 1800 mm, ID = 200 mm;
• Gas and vacuum tight housing, end flanges NW150;
• Connections for gas inlet and vacuum;
• A step motor drives the movement of the crucible holder;
• 2 thermocouples (of type С, one at the heating conductor and in the crucible holder each).

The systems for vertical zone melting works with an additional movable heater. This heater first melts the metal in the cone point of the crucible, and then moves upwards very slowly, with a ring in the liquid metal going up too.

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