A thermodynamic calculation procedure was developed to describe the fundamental properties of plasmas and to predict possible products in thermal plasma processing. This procedure consists of two steps: One is to describe thermodynamic properties of monoatomic molecular species by statistical calculation, and the other is to calculate thermal equilibria among possible species in various phases. Any solution model, whether it is ideal or regular, can be adopted in this procedure. This procedure was applied to the synthesis of Y-Ba-Cu-O fine powder by the evaporation-condensation method in oxygen plasma. The calculated results have revealed that the high vapor pressure of BaO(g) suppresses the precipitation of Y2O3(s) and makes co-condensation of the liquid homogeneous ternary oxide mixture possible. While the addition of a small amount of metal has little effect on the enthalpy of plasma, it affects the electrical conductivity drastically in the region from 4000 to 11000 K.
(Received May 25, 1989)
Keywords: thermodynamics, thermal plasma, plasma evaporation, fine powder, yttrium-barium-copper-oxygen
*R&D Laboratories-I, Nippon Steel Corporation, Kawasaki 211, Japan.