Experimental and computational study on the phase stability of Al-containing cubic transition metal nitrides

The phase stability of Al-containing cubic transition metal (TM) nitrides, where Al substitutes for TM (i.e. TM_1−xAl_xN), is studied as a function of the TM valence electron concentration (VEC). X-ray diffraction and thermal analyses data of magnetron sputtered Ti_1−xAl_xN, V_1−xAl_xN and Cr_1−xAl_xN films indicate increasing phase stability of cubic TM_1−xAl_xN at larger Al contents and higher temperatures with increasing TM VEC. These experimental findings can be understood based on first principle investigations of ternary cubic TM_1−xAl_xN with TM = Sc, Ti, V, Cr, Y, Zr and Nb where the TM VEC and the lattice strain are systematically varied.

However, our experimental data indicate that, in addition to the decomposition energetics (cubic TM_1−xAl_xN → cubic TMN + hexagonal AlN), future stability models have to include nitrogen release as one of the mechanisms that critically determine the overall phase stability of TM_1−xAl_xN.