Powder feeder for crystals of large diameter grown by the verneuil technique

Abstract

AbstractTo grow crystals of large diameter ( ≈ 50 mm) by the flame fusion process it is necessary to feed powder with a flow rate of ≈ 2 g/min into the gas stream, the grain size being as small as possible. The properties of vertically and horizontally excitated sieves are compared. A sieve arrangement with horizontal and vertical vibration is described, which at a mesh width of 90 μm has a powder flow of up to 5 g/min. The long range constancy was within ± 8%. Sieves with a mesh width < 90 μm can be used if an ultrasonic disintegrator is mounted above the feeder sieve. Sapphire and Mg–Al spinel crystals up to 65 mm in diameter could be grown.