Sm(2-x)Dy(x)Zr2O7 pyrochlores: probing order-disorder dynamics and multifunctionality

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• The synthesis and characterization of rare-earth zirconate pyrochlores are crucial for advanced material applications.
• Understanding structure-property relationships in Sm2Zr2O7 and Dy2Zr2O7 systems is key for optimizing their performance.

Purpose of the Study:

• To synthesize Sm(2-x)Dy(x)Zr(2)O(7) compounds using a gel combustion method.
• To investigate the structural, optical, and ionic conductivity properties of these doped zirconates.
• To explore their potential as photocatalysts for organic pollutant degradation.

Main Methods:

• Controlled gel combustion synthesis of Sm(2-x)Dy(x)Zr(2)O(7) powders.
• Characterization using powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-Vis spectroscopy.
• Ionic conductivity measurements and first-principles calculations.

Main Results:

• Single-phase pyrochlore structure observed up to 40 mol% Dy(3+), transitioning to a defect fluorite structure.
• Raman spectroscopy indicated pyrochlore ordering throughout the composition range, contradicting XRD findings for Dy2Zr2O7.
• Ionic conductivity increased with Dy(3+) content, accompanied by higher activation energy due to disorder.
• Tunable band gap observed, decreasing with increasing Dy(3+) concentration, supported by theoretical calculations.
• Demonstrated high photocatalytic activity for xylenol orange degradation, with efficiency increasing from Sm2Zr2O7 to Dy2Zr2O7.

Conclusions:

• The study successfully synthesized Sm(2-x)Dy(x)Zr(2)O(7) compounds with tunable properties.
• Structural analysis revealed a phase transition from pyrochlore to defect fluorite, with Raman spectroscopy offering complementary insights.
• The materials exhibit promising potential as efficient photocatalysts, particularly Dy-rich compositions.