Thermodynamic properties and electrical conductivity of Ta3N5 and TaON

TaON and Ta3N5 powders and thin films were prepared from Ta2O5 powders and tantalum thin films by equilibrating specimens with ammonia-bearing gas mixtures at 1100°K. TaON was found to be nonstoichiometric and to have semiconducting properties. The free energy of formation of TaO1.05N0.95, which is the composition in equilibrium with Ta2O5, is -94.1± 5 kcal per mole. The range of electrical conductivity observed at room temperature was 10-3 to 5 (ohm-cm)-1. Ta3N5 has a free energy of formation of -65 ± 10 kcal per mole, and its electrical conductivity is 1.3 x 10-4 (ohm-cm)-1.