METHOD OF PREPARING COLORED MONOCRYSTALS (VERSIONS) Russian patent published in 1999 - IPC

FIELD: crystal growing. SUBSTANCE: charge is composed, wt.%: Y₂O₃, 10-40; Nd₂O, 3-8; CeO₂, 2-4; and ZrO₂, the balance, is placed in container with cooled walls. Charge is then heated to form melt in wall accretion layer. Oriented crystallization of melt is accomplished when container is displaced relative to heating zone, after which container is withdrawn from heating zone and monocrystals are cooled. Further, monocrystals are annealed in inert or reduced atmosphere at pressure from 10^-4 to 10^-3 mm Hg and temperature 500 to 1600 C for 1-2 h, whereupon temperature is lowered with the rate 400 to 1000 C/h. In another version, charge contains, wt.%: Y₂O₃, 10-40; Nd₂O₃, 1-4; P₂O₃, 2-8; and ZrO₂, the balance. To achieve red color with alexandrite effect, monocrystals are annealed in inert or reduced atmosphere at temperatures 1200 to 1400 C for 1-2 h, after which temperature is lowered with the rate 400 to 1000 C/h. EFFECT: achieved precious red color. 6 cl, 1 dwg