Thermodynamic analysis of reactions in the Al-N-Ta and Al-N-V systems

The Al-N-Ta and Al-N-V ternary phase diagrams are calculated from the thermodynamic parameters of the corresponding binary systems. For the Al-N-Ta system, the direct extrapolation from the binary edges can describe the experimental information on the isothermal sections at 1000, 1250 and 1500 °C from the literature. In the case of the Al-N-V system, it is shown that the direct extrapolation from the binary edges can describe the experimental isothermal section at 1300 °C from the literature. For the isothermal section at 1000 °C, however, the extrapolation does not reproduce the reported AlN + (V) + VNx phase equilibrium. The calculated Al-N-Ta and Al-N-V phase diagrams are also compared with the phase assemblage resulting from our own thin film diffusion couples Ta/AlN and V/AlN. It is plausible that these assemblage data are associated with intermediate states approaching true equilibrium states.