Abstract: Two dimensional equation describing heat conduction-radiation of Al₂O₃ single crystal was
established by light-guide model. The temperature field was calculated by finite-element method and its features were also discussed. Finally, the
theoretical result was compared with the experimental result. The convection coefficient has little effect on the temperature of crystal near the
solid-liquid interface, while it affects the temperature of crystal significantly which is far from the interface. The temperature gradient
near the solid-liquid interface increases with the growth rate increasing. The temperature curves of crystals with different length show that the
temperature changes little when the crystal is long, and the temperature field of crystal can be regarded as a quasistatic one.

Key words: Al₂O₃ crystal, temperature field, multiple heat exchange, finite-element method