Nitrogen content-dependent densification behavior and ablation resistance of ZrC_xN_y solid solutions

Zirconium carbonitride (ZrC_xN_y) solid solutions with designed nitrogen contents (y = 0.25, 0.5 and 0.75) were synthesized via ball milling of ZrC and ZrN powders, followed by reactive spark plasma sintering. The effects of nitrogen doping on phase formation, densification, and ultra-high-temperature ablation resistance were systematically investigated. XRD and XPS results supported the formation of a predominant ZrC_xN_y solid-solution phase, as evidenced by systematic lattice parameter contraction and composition-dependent binding energy shifts. Microstructural analyses showed that nitrogen-containing compositions achieved relative densities above 96%, suggesting improved densification under the present SPS conditions. This improvement is tentatively associated with nitrogen-related changes in lattice distortion, defect chemistry, and anion-sublattice mass transport. Ablation tests using a supersonic plasma torch at 2200 °C revealed a composition-dependent performance trade-off: among ZrC_xN_y solid-solution samples, ZrC_0.5N_0.5 exhibited the lowest mass ablation rate (0.56 mg (Formula presented)), whereas ZrC_0.75N_0.25 demonstrated the lowest linear ablation (0.46 μm (Formula presented)) and linear degradation (2.17 μm (Formula presented)) rates, benefiting from a denser and more adherent ablation layer. These findings highlight that tailored nitrogen doping is an effective strategy for optimizing the microstructural and thermo-structural properties of zirconium carbide for extreme environment applications.