Synthesis and Properties of Bulk Mg₃WN₄ in a Wurtzite-Derived Structure

Area of Science:

• Materials Science
• Solid-State Chemistry
• Inorganic Synthesis

Background:

• Ternary nitrides are promising materials for applications requiring specific properties like ion transport.
• The Mg-W-N system has theoretical predictions and recent syntheses of various compounds.
• Controlled synthesis of novel materials is key to unlocking their potential.

Purpose of the Study:

• To report the first bulk synthesis of Mg3WN4.
• To investigate the synthesis mechanism and crystal structure.
• To explore methods for achieving phase-pure ternary nitrides.

Main Methods:

• Solid-state metathesis reaction using Li6WN4 and MgCl2 precursors.
• In situ synchrotron powder X-ray diffraction to monitor reaction progress.
• Ex situ synthesis with controlled thermal budget and excess MgCl2.
• Second-harmonic generation, optical absorption, chemical analysis, and electron microscopy for characterization.

Main Results:

• Successful bulk synthesis of Mg3WN4 in a wurtzite-derived structure.
• Identified reaction temperatures and competing phase formation (disordered rocksalt-derived (Mg,W)N).
• Confirmed cation-ordered structure and polar symmetry of Mg3WN4.
• Observed defect formation in metathesis-synthesized bulk material.

Conclusions:

• Selective ex situ synthesis of phase-pure Mg3WN4 is achievable.
• In situ monitoring is crucial for optimizing synthesis conditions.
• Controlled thermal budget is essential for targeted phase formation.
• This work enables further property characterization of Mg3WN4.