Structural chemistry of M2Si5N8:Eu2+ (M = Ca, Sr, Ba) phosphor via structural refinement

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Nitrides doped with divalent europium (Eu2+) are crucial for red-emitting phosphors.
• Understanding ion distribution in the host lattice is key to optimizing luminescence properties.

Purpose of the Study:

• To determine the preferential substitution sites and occupancy of Eu2+ ions in alkaline earth co-doped M2Si5N8:Eu2+ (M = Ca, Sr, Ba).
• To elucidate the structural and electronic factors governing the red emission in these nitride phosphors.

Main Methods:

• X-ray powder diffraction (XRD) for structural refinement.
• Quantum mechanics-based geometry energy calculations (density-functional theory) to confirm preferential sites.
• Carbothermal reaction method for phosphor synthesis.

Main Results:

• Eu2+ ions preferentially occupy nine-coordinated sites within the M2Si5N8 host lattice.
• Refined structural model in space group Pmn2, with specific lattice parameters.
• Quantified Eu2+ occupancy at M(1) (0.10(2)) and M(2) (0.04(2)) sites.

Conclusions:

• The study confirms the nine-coordinated nitrogen site as the preferential location for Eu2+ substitution.
• The findings provide critical insights into the structure-property relationships of M2Si5N8:Eu2+ red-emitting phosphors.
• This work aids in the rational design of efficient nitride-based luminescent materials.