Study of CeI3 evaporation in the presence of group 13 metal-iodides

The influences of GaI3, InI, and TlI on the evaporation characteristics of CeI3 have been studied over the temperature range 900 K to 1400 K using x-ray induced fluorescence. The total vapor densities, summed over all atomic and molecular species, of Ce, I, In, and Tl were obtained. Measurements of Ce were limited to temperatures above 1033 K, the melting temperature of CeI3. This is the highest temperature range for which measurements of the vapor pressure of CeI3 have been made. The vapor pressure of the CeI3 monomer above the pure CeI3 salt for temperatures exceeding its melting point can be approximated by log10p/Pa=11.24(±0.03)−10,690(±40) (T/K)−1 where the numbers in parentheses are standard uncertainties. InI and TlI were shown to modestly enhance the presence of Ce in the vapor phase, up to a factor of 5. GaI3 produced no enhancement in this temperature range. Numerical simulations of the thermochemical equilibrium suggest the importance of both liquid-phase and vapor-phase complexes. Significant improvement to the method of absolute calibration is discussed.