The system boron-carbon-hafnium-zirconium is of interest in the aeronautical and nuclear industries due to the widely applied ultra-high temperature ceramics compounds found in this combination of elements. These materials have extremely high melting temperatures, and maintain strength even at very high temperatures. For these applications, it is necessary to have a good understanding of the phase stability of the material as a function of temperature, composition, and even pressure.
Using the CALPHAD approach, the B-C-Hf-Zr system is examined, with the aim of developing a consistent quaternary thermodynamic database. This is done by taking into account all experimental and accurately modelled data of the physical and thermodynamic properties related to the phase stability of this system. Particular attention is paid to fully anharmonic first principles calculations of the thermodynamic properties of the binary carbides and borides, and the use of crystallographic experimental investigations in the sublattice modelling of phases.