The structure of the ordered phase in rocksalt type titanium carbide, carbidenitride, and carbidehydride

It is shown that on the basis of the disordered delta-phase (space group Fm3m) two ordered equilibrium phases with cubic (delta'-phase, space group Fd3m) and trigonal (delta ''-phase, space group R3m or P3(1)21) unit cells can be formed in titanium carbide TiC0.62 and carbidenitrides TiCxNy (a + y approximate to 0.63), whereas only a cubic delta'-phase has been observed in TiC0.62Hy. With increasing temperature the low temperature trigonal delta ''-phase transforms at about 1053 K to the cubic delta'-phase which experiences disordering. The formation of the cubic delta'-phase at temperatures lower than 1053 K is explained by the difference between the order of delta-->delta' and delta-->delta '' phase transitions.