Synthesis of hexagonal Ni(3)N using high pressures and temperatures

Area of Science:

• Materials Science
• Solid-State Chemistry
• High-Pressure Synthesis

Background:

• The hexagonal Ni3N phase is the sole known bulk nickel nitride stable at ambient pressure.
• Understanding the formation and stability of nickel nitride under extreme conditions is crucial for materials science.

Purpose of the Study:

• To synthesize and characterize the hexagonal Ni3N phase under high-pressure and high-temperature conditions.
• To investigate the factors influencing nickel nitride formation and stability.
• To explore potential new nitride phases formed during high-pressure experiments.

Main Methods:

• Multianvil press experiments were conducted at 20 GPa and 2000 K.
• Starting materials included nickel (Ni) and sodium azide (NaN3).
• Ex situ analysis utilized transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Main Results:

• Hexagonal Ni3N (space group P6(3)22) was successfully synthesized and recovered at ambient pressure.
• The formation of Ni3N is linked to repulsive nitrogen-nitrogen interactions and thermal stability.
• A novel sodium rhenium nitride phase was also observed.

Conclusions:

• High-pressure synthesis provides a viable route to recover ambient-stable Ni3N.
• Repulsive nitrogen ion interactions and thermal stability are key factors in nickel nitride formation.
• This study contributes to the understanding of interstitial nitrides under extreme conditions.