Machines for growing of sapphire and ruby monocrystals per Bridgman-Stockbarger method

A monocrystal is grown in a crucible, the form and dimensions of which shape those of the final crystal. The seed is placed in the lower part of the crucible; the melting degree serves as a direct indicator of whether it is possible to initiate the growing process of the crystal. The required axial temperature gradient is defined both by the thermal node itself and by the crucible moving towards the cold area thus ensuring the proper heat dissipation and high temperature gradient along the crystal axis.
 
As long as Bridgman-Stockbarger methodoperates in bottom-up direction, bubbles and impurities are removed from the crystal by the crystallization front. This technique enables to grow crystals at higher speed with less pinhole defect and bubbles.
 
The crucible with the crystal can be rotated at speed of 5…30 rpm. The rotation is used to balance thermal conditions inside the crucible; at the same time, the centrifugal force pushes impurities and bubbles closer to the walls of the crucible.

Growing of rubies requires well-prepared raw material. To achieve this goal the powder Al₂O₃ is thoroughly mixed with alloying element Cr₂O₃. Then the created mixture is pressed in tablets 5…10 mm via tableting machine. This machine can be ordered with the entire facility.

The facility is equipped with the leak proof gas extraction system to relieve the gas from the chamber prior to any opening. The hardware is manufactured on request under approved Technical assignment. Any parameters can be changed at your convenience.

Benefits of machines for growing of sapphire and ruby monocrystals per Bridgman-Stockbarger method produced by the “NPO “GKMP” LLC

• Growing per any crystallographic axis, including C-axis (0001)
• Automatically driven process, including seed placement
• TV cameras, pyrometers or thermocouples are not required
• Highly qualified operators are not required
• The furnace requires just maintenance: removal of the crystal, furnace cleaning, loading of raw material

Property	Meaning
Crystal diameter, mm, not to exceed	160
Crystal length, mm	250
Crystal mass, mm	24
Internal chamber diameter, mm	800
Chamber height, mm	1100
Ultimate vacuum inside chamber, torr	5*10-5
Internal gas over pressure (Ar, N2, CO2), kg/cm2	1.0
Travelspeed (melting sensor), mm/min	50
Stroke (melting sensor), mm	720
Crucible. Travel speed (operating), mm/h	0.1…10(±1%)
Crucible. Travel speed (accelerated), mm/min	50
Crucible. Stroke, mm	400
Crucible. Rotation speed, rpm	1…30(±1%)
Crucible. Max load to the rod, kg	300
Heater temperature (operating), ºС	2200
Heater material	tungsten
Internal operating vacuum, torr	1.0*10-5
Vacuum. ТМН pumping speed (nitrogen), l/s	700
Vacuum. Fore pumping speed, m3/h	1.0*10-5
Internal gas over pressure (Ar, N2, СО2), not to exceed kg/cm2	1.0
Gas flow rate (Ar, N2, СО2), nl/min	1...100
Cooling. Inlet water pressure, kg/cm2	2...3
Cooling. Water flow rate (overall), m3/h	4...6
Power circuit and control cabinet power supply	3*(380±38)
Power network frequency, Hz	50/60
Fixed power, kW	63
Nominal heater power, kW	45
Heater power voltage, V	0-14
Control. Constant power accuracy, %	±0.1
Control cabinet power, kW not to exceed	7
Height, mm	5000
Length, mm	3000
Width, mm	2000
Mass, not to exceed, kg	3000
Mass, not to exceed, kg	500