NaGaPO₄F - a KTiOPO₄-structured solid sodium-ion conductor

Area of Science:

• Materials Science
• Solid-State Chemistry
• Energy Storage

Background:

• Advanced ionic conductors are essential for technologies like solid-state ion batteries and fuel cells.
• The KTiOPO4 structural family is known for its potential in ionic conductivity.

Purpose of the Study:

• To synthesize and characterize a novel sodium-ion conducting material, NaGaPO4F.
• To investigate the sodium-ion mobility and structural properties of NaGaPO4F.

Main Methods:

• Facile two-step synthesis involving hydrothermal preparation and ion exchange.
• Crystal structure refinement using synchrotron X-ray powder diffraction and electron diffraction tomography.
• Investigation of Na-ion mobility via solid-state nuclear magnetic resonance (NMR) and density functional theory (DFT) calculations.

Main Results:

• NaGaPO4F was synthesized for the first time and its crystal structure determined.
• The material exhibits excellent thermal stability up to 450 °C with minimal cell volume expansion.
• DFT and NMR studies revealed 3D sodium diffusion with low migration barriers (0.22-0.5 eV) and a bandgap of ~4.25 eV.

Conclusions:

• NaGaPO4F is a thermally stable, novel sodium-ion conductor.
• The 3D diffusion pathways and low migration barriers indicate its potential for fast sodium-ion conduction.
• This discovery opens avenues for developing new materials for sodium-ion based energy storage devices.