| 摘要 |
In the present invention, there is disclosed a process for preparing single crystals of laser grade, of large diameters up to 500 mm, based on aluminates of garnet with yttrium and/or lutetium with doping of rare earth metal oxides and some transient metals of the general composition Yi3Ali5Oi12, Lui3Ali5Oi12, Yi(3-x)(RE)ixAli5Oi12, optionally Lui(3-x)(RE)ixAli5Oi12, wherein (RE) are rare earth metals Nd, Sm, Eu, Ho, Er, Tm, Yb and x is 0 to 3 in a crucible situated within a furnace. The invention is characterized in that a single crystal seed with a cross section of at least 100 mme2 is oriented such that the geometrical axis thereof is perpendicular to a crystallographic surface of an ideal crystal with the largest surface and with maximally possible crystal symmetry from the surfaces being available. The single crystal seed rotates at a rate of 0.1 to 20 revolutions per minute and is drawn at a rate of 0.08 to 5 mm/hour at maintaining of the crystal bottom surface, optionally convex or concave shape of a flat interface with the vertex angle within the range of 175 degrees to 185 degrees by adjusting the crystal drawing rate, rotation rate and temperature control at the crystal/melt interface based on optical, weight or visual monitoring. After the crystal cone diameter expansion of up to at least 80 percent of the crucible diameter is achieved, the rotation rate is increased at least by 50 percent under simultaneous maintenance of the crystal bottom surface with the vertex angle within the range of 175 degrees to 185 degrees by adjusting the crystal drawing rate, rotation speed and temperature control at the crystal/melt interface based on optical, weight or visual monitoring. After the crystal required weight is achieved, the electric input up to by 10 percent is increased at simultaneous maintenance of the crystal rotation rate and at the same time, the crystal is drawn at a rate of 5 to 10 mm per minute above the rest of melt. Subsequently the crystal is in that position programmable tempered for s period of at least two hours at a temperature of at least 100 degC below the crystal melting point, then it is further cooled down to a room temperature with an average temperature gradient 100 degC/hour within the growth zone in the crucible underneath the lid. |
