Features of Zr-rich corner of the Zr-N-O ternary system by controlled low-pressure oxidation and thermodynamic analysis

In order to clarify the Zr-rich corner of the Zr-N-O ternary system, a series of nitridation and controlled low-pressure oxidation heatings were made on zirconium metal plates. The experiments were made in separated reaction sequences, which were (1) oxidation of pre-nitrided zirconium, and (2) simultaneous nitridation and oxidation of zirconium. Low-partial pressures of oxygen were obtained by using a redox couple of either Mo/MoO2 or Cu2O/CuO. The samples were characterized by X-ray diffraction, optical microscopy, and electron probe micro analysis. Experimental results were coupled with a preliminary thermodynamic analysis with a sublattice formalism to draw a provisional ternary isotherm at 1373K.