Determination of standard gibbs energies of formation of Cr2N and CrN

Abstract

The standard Gibbs energies of formation of Cr2N and CrN have been measured by an equilibration technique and by using thermogravimetry and differential thermal analysis (TG-DTA) at temperatures ranging from 1232 to 1523 K. The results are expressed as follows: $$\begin{gathered} 2Cr(s) + \frac{1}{2}N_2 (g) = Cr_2 N(s) \hfill \\ \Delta G^ \circ = - 104,000( \pm 1300) + 47.7( \pm 5.9)T({J \mathord{\left/ {\vphantom {J {mol}}} \right. \kern-\nulldelimiterspace} {mol}}) (1362 to 1523 K) \hfill \\ Cr(s) + \frac{1}{2}N_2 (g) = CrN (s) \hfill \\ \Delta G^ \circ = - 117,000( \pm 1000) + 71.9( \pm 4.9) T({J \mathord{\left/ {\vphantom {J {mol}}} \right. \kern-\nulldelimiterspace} {mol}}) (1232 to 1354 K) \hfill \\ \end{gathered} $$ The standard Gibbs energies of formation of Cr2N and CrN determined by the present work are more negative than the values in the JANAF Tables by about 14 and 5 kJ/mol, respectively, in the measured temperature range.