Structural Ordering and Charge Variation Induced by Cation Substitution in (Sr,Ca)AlSiN3:Eu Phosphor

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Nitride phosphors are crucial for white light-emitting diode (LED) applications.
• Optimizing phosphor performance requires structural modifications to enhance luminescent properties.

Purpose of the Study:

• To investigate the effects of cation substitution (Sr2+ for Ca2+) on the structure and luminescence of nitride phosphors.
• To understand how structural changes influence charge variation, lattice distortion, and thermal stability.

Main Methods:

• Cation substitution (Sr2+ for Ca2+) in SrxCa0.993-xAlSiN3:Eu(2+)0.007 phosphors.
• X-ray absorption near-edge structure (XANES) spectroscopy to detect activator charge variation.
• High-resolution transmission electron microscopy (HRTEM) for microstructure analysis.
• Solid-state Raman spectroscopy and nuclear magnetic resonance (NMR) spectroscopy to analyze structural changes and cluster ordering.

Main Results:

• Strontium substitution expanded the lattice and altered inter-layer distances, inducing lattice distortion.
• XANES confirmed charge variation of activators, facilitating enhanced photoluminescent intensity (>10%) and a blue shift.
• HRTEM, Raman, and NMR revealed changes in anion environment, ordering of SiN4 and AlN4 clusters, and neighbor sequences.
• Improved thermal stability was observed, with a 10% enhancement at 473 K for specific compositions.

Conclusions:

• Cation substitution effectively modifies nitride phosphor structure, leading to enhanced luminescence and improved thermal stability.
• The study highlights the importance of controlling neighbor sequences and local coordination environments for optimizing phosphor performance.
• These findings advance the development of advanced materials for solid-state lighting.