ИСТИНА

Single crystals of ruby with size up to 2.5 cm have been obtained from fluxed melts based on the systems Li2O - MoO3, Li2 O- WO3, Na2O - WO3, 2PbO - 3V2O5, PbO - V2O5 - WO3, PbF2 - Bi2O3 and Na3AlF6 by both the top-seeded solution growth method and spontaneous crystallization at temperatures 1330 - 900oC. Al2O3 solubility has been measured for the flux composition of 2Bi2O3 - 5PbF2 in the temperature range 1200-1000OC and dissolution enthalpy has been found as 29.4 KJ/Mol. The composition of grown crystals was studied by electron microprobe analysis. The synthetic ruby contains from 0.51 to 6.38 at % of chromium admixture depending on the crystal growth conditions. As a rule, chromium uniformly distributed over the entire volume of grown crystals. Mo, W, Pb and Bi concentration in grown crystals does not exceed 0.01 wt %. The amount of vanadium impurities varies from 0.02 to 0.06 at %. The crystallographic forms {0001}, {01-12}, {11-23}, {10-14}, {10-10} and {10-10} are distinguishing features of the crystals grown. Synthetic crystals obtained within 1150 - 900oC have a plate-like habit with a strongly developed pinacoid, except the crystallization of ruby from Li-enriched fluxed melts at elevated temperatures. Ruby crystals tend to grow with more equidimensional shape in the interval of 1330 - 1100oC. In this case, the {0001} faces are rarely developed. Increasing WO3 concentration in PbO - V2O5 - WO3 system also promotes more isometric ruby crystals.