Numerical Simulation Analysis Of Czochralski Growth Processes For Langasite Crystal

Crystalline La₃Ga₅SiO₁₄ (langasite, LGS) was first reported as a laser crystal in early eighties, Crystalline LGS was widely studied as a promising piezoelectic material later. Many papers have reported its crystal growth peculiarities and piezoelectic properties. The EO properties of LGS have been measured by some experiments and the results showed LGS possessed workable EO coefficients, it was also used as EO crystal and make new EO Q-switch.Among crystal growth methods, the Czochralski single crystal growth method is a good commercial one for growing the high-optical-quality LGS crystal. The defects and their affection on the crystal's properties such as cracks and growth core in the crystal have been discussed. The resolvents acoording to the defects are presented. Some key factors having influence on crystal growth are summed up and they are the composing of raw materials, technics, temperature and time of treating with melt of the raw materials, etc. The dimension of the as-grown LGS crystal with flat shoulder is approximatelyΦ50mm×100mm. The crystal is transparent and in dark orange. Obvious cracks or inclusions are not observed.The finite element software CGSim (Crystal Growth Simulation) Multiphysics is employed to simulate the melt temperature and velocity distribution during an inductively heated of LGS crystal growth process using CZ. The simulation is planar in whole system.The TDL-L50 single crystal growth furnace designed by Xian university was the prototype to simulate the different crystal growth stage in the quasi-steady state, by physical simplifying assumption, building a geometric model used CGSim and selecting appropriate parameters. Moreover, the change of temperature and velocity field and variety of the shape of solid-liquid interface in the crystal stage were discussed. In addition, we analyzed the relationship that between the rotation speed of the crystal and crucible and the crystal growth. Also we found that different kinds of the crystal, the diameter of the crucible and after heater had effect on the temperature field. The factors effected the temperature and velocity field have been analyzed. It is showed that the whole crystal growth stage by simulate.It is concluded that the heat loss from the increasing the length of the crystal results in the similarity of solid-liquid interface to the melts; Diameter of 45mm of crystal with plane inter face was got at revolution of 9-12r, in platinum crucible with special size; After heater could decrease temperature gradient of crystal apparently. Axial temperature gradient of crystal is about 7.5 K /cm by using platinic after heater, whereas that of crystal is about 13.9 K/cm without after heater; Temperature gradient in shoulder is larger for crystal growth in inclined shoulder.These results could be important parameters to control the Czochralski single crystal growth, and act a foundation of the theory of single crystal growth.