CRYSTAL PERFECTION OF ALPHA-AL203 AS A FUNCTION OF GROWTH METHOD.

Synthetic ruby and sapphire crystals grown by flame-fusion and flux methods are described and discussed in terms of growth method and growth techniques. Dislocation densities are given for all samples, and comparisons are made in an attempt to obtain correlation between the growth method used and the resulting lattice defect structure. Data are presented for crystals grown by various methods, namely, Verneuil, flux, hydrothermal, electron-beam zone refining, Czochralski, vapor deposition, and plasma torch methods. Dislocation density evaluation is based on chemical etchpit analysis, which produced average dislocation density values varying from about 1,000,000sq cm for crystals grown by the plasma torch method to about 1000sq cm for crystals grown by the electron-beam method. Crystals grown by the other methods mentioned about show dislocation densities lying between these values. A brief description is presented of the chemical etching techniques and apparatus used at AFCRL. Author