Edge defined crystal growth

Edge-defined film growth. A modification of the czochralski TECHNIQUE (q.v.) for growing single crystals. In the EFG technique a new die with a capillary hole is immersed in the melt, which is wicked to the top of the die by surface tension. A seed crystal is touched to its surface there, and slowly pulled away. A film of the melt spreads over the top of the die, and the growing crystal assumes the cross-sectional shape defined by the sharp edges of the die. Shapes similar to extruded cross-sections can be produced. 

A continuous monocrystalline sapphire (A1203) fibre has been prepared as single-crystal fibres by LaBelle and Mlavsky using a modified czochralski puller and radio frequency heating. The technique adopted in this method is called edge-defined film-fed growth (EFG) [18-22], Figure 3.4 shows a schematic of the EFG method. 

Edge defined, film-fed, growth process for making a single-crystal alumina fibre (reproduced by permission of Chapman Hall)56. 

Figure 6.11 Schematic of the edge-defined fihn-fed growth (EFG) method of making a single crystal alumina fiber.

Saphikon Saphikon 100% AI2O3 3.96 single-crystal a-Al203 125 mono filament edge defined film- fed growth 470 3.5 9 developmental fibers... 

Continuous single crystal fibers can be grown from inviscid melts by two relatively slow processes the edge defined film fed growth (EFG) process [13] and the laser heated float zone (LHFZ) or laser heated pedestal growth (LHPG) process [14]. Both offer growth rates of toO.3-0.7 mm/s [13-14]. 

Edge defined film fed growth (EFG) is a commercial process [13] that facilitates the fabrication of continuous void free single crystal oxide fibers (Figure 16) from tungsten or other growth orifices. 

Figure 16. Edge defined film fed growth process (schematic drawing). Redrawn from J. Monbleau, Single-crystal technology, Product Bulletin, Saphikon Inc., Milford, NH (1994).

Three processes are known to fabricate continuous yttrium aluminum garnet (YAG) fibers. Single crystal YAG fibers are obtained by the edge defined film fed growth process and by the laser heated float zone process (Chapter 4.5). Both are slow processes. Amorphous YAG glass fibers have recently been demonstrated by a containerless laser heated melt process (Chapter 4.4). Polycrystalllne YAG fibers can be obtained with sol-gel and related processes (this chapter). These are potentially fast processes. 

EFG Edge-defined Film-fed Growth technique Crystal "Ir crucible... 

LaBell, Jr., H.E., Growth of Controlled Profile Crystals from the Melt Part II - Edge-Defined, Film-Fed Growth [EFG]. Mat. Res. Bull. 6 581-590 (1971). 

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