Temperature and emissivity measurements at the sapphire single crystal fiber growth process

We present a new method for evaluation the absorption coefficient of the crystal melt around the phase transition zone for the spectral range of semitransparency. The emissivity distribution across the crystallization front of the sapphire crystal fiber was measured at the quasi-stationary laser heated pedestal growth (LHPG) process (Fejer et al., 1984; Feigelson, 1986) and the data for solid state, melt and phase transition zone (melt-solid interface) were obtained. The sapphire melt absorption coefficient was estimated to be 14 ± 2 cm−1 in the spectral range 1-1.4 μm around the melt point. It is consistent with data, obtained by different other methods. This method can be applied to determine the absorption coefficient for other materials.