Effect of ordering on the structure and heat capacity of cubic vanadium carbonitrides VCxNy

Experimental results are presented on measurements of the crystal structure and heat capacity of nonstoichiometric cubic vanadium carbonitrides VC_xN_y (x + y = 0.85) in the region of disorder-order phase transitions. It is found that ordered phases V₆(C,N)₅□ and V₈(C,N)₇□ with the structures of the V₆C₅ and V₈C₇ types form in vanadium carbonitrides at a temperature of ~1100 K through the first-order phase transition mechanism. The channels of disorder-order transitions are determined. It is found that, in the nonmetal sublattice of the detected ordered phases, C and N atoms form one sublattice and structural vacancies □ form another sublattice. C and N atoms are randomly distributed in their sublattice.