Anion-Stabilized Incommensurate Modulation Enables Nonlinear Optical Response in Eu2SiO3.89N0.11

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Silicates possess high structure plasticity, but complex aperiodic states are typically limited to high temperatures.
• Stabilizing these aperiodic structures at ambient conditions is crucial for material applications.

Purpose of the Study:

• To synthesize and characterize a nitrogen-doped europium silicate (Eu2SiO4) phase.
• To investigate the effect of nitrogen incorporation on the silicate structure and its properties.
• To explore anion engineering as a strategy for stabilizing complex structures.

Main Methods:

• Synthesis of nitrogen-doped Eu2SiO4.
• Multimodal structure analysis to determine crystal structure and atomic arrangements.
• Analysis of bond valence, bond lengths, and local distortions.
• Characterization of optical properties, including second-harmonic generation and birefringence.

Main Results:

• Nitrogen incorporation stabilized an incommensurately modulated structure at ambient conditions (q = 0.284(3)a*).
• Nitrogen preferentially occupied oxygen sites, altering local coordination and stabilizing the modulated phase.
• Anion-induced polar displacements resulted in observable second-harmonic generation and birefringence.

Conclusions:

• Subtle anion engineering is an effective strategy for stabilizing complex aperiodic structures.
• Nitrogen doping provides a new pathway for designing functional mixed-anion materials.
• The stabilized modulated structure in Eu2SiO4 exhibits significant optical responses.