CsI crystal growth by continuous feed method
Temperature distribution in the crystallization zone, flow pattern
in the melt and gas region, and temperature gradient in
Due to very high diathermancy of the alkali-halide single crystals (AHC),
thermal field analysis should be made accounting for the radiative heat
transfer in both the crystal and the melt, together with convective and
conductive heat transfer modes. Besides, the sublimate layer precipitating
on the crystal and the furnace inner surfaces noticeably contributes
to the heat transfer in the setup, affecting, in particular, the temperature
field in the crystal. A numerical model was suggested for the conjugated
analysis of heat exchange, melt and gas flows in the growth setup with
the account of radiative heat transport in the semitransparent crystal and
melt media. The crystal was assumed to be
covered by an opaque deposit layer of 1 mm in thickness.
Exposed regions had an area of only about 20 mm around
the seed and another 10 mm area at the melt/crystal
interface, as is typical for the experiment.
CsI crystal growth.
Physical characteristics of CsI
λ = 1.1 W/m*K
Cp = 200 J/kg*K
ε = 0.91
transparency band is 0 - 3.2 μm
α = 0.05 m-1
refractive index is 1.75
λ = 5 W/m*K
Cp = 100 J/kg*K
μ = 0.05 kg/m*sec
ε = 0.9
transparency band is 0 - 2 μm
α = 2.5 m-1
refractive index is 1.7
λ = 0.2 W/m*K
ε = 0.5
The results were verifyed using detailed measurements of the thermal
field evolution inside an industrial setup for the growth of 300-315 mm CsI(Na)
Being in close
quantitative agreement with the experimental data, the
simulation results illustrate a detailed temperature
distribution in the crystal together with non-linear changes
in the temperature gradient.
Fig. 3. The distribution
of temperature and axial temperature gradient along the crystal side
at different growth stages (a). The temperature distribution along
the crystal top at different growth stages. The solid red line stands for
the computation (b).
1. "Thermal conditions for large alkali-halide crystal growth by the continuous
V. V. Vasilyev, V. I. Goriletsky, O. Ts. Sidletskiy, E. N. Bystrova, V. V. Kalaev,
Submitted to Elsevier Science.