Structural and optical characterization of Er-doped CaMoO₄ down-converting phosphors

Area of Science:

• Materials Science
• Solid-State Chemistry
• Nanotechnology

Background:

• Calcium molybdate (CaMoO4) is a known phosphor with intrinsic luminescence properties.
• Rare-earth element doping is a common strategy to tune the optical properties of host materials.
• Erbium oxide (Er2O3) is frequently used for its characteristic emission spectra.

Purpose of the Study:

• To synthesize Er2O3-doped CaMoO4 nanoparticles.
• To investigate the structural and optical properties of these doped nanoparticles.
• To evaluate their potential for optical device applications.

Main Methods:

• Solid-state sintering at 800°C to synthesize Er2O3-CaMoO4 nanoparticles.
• X-ray diffraction (XRD) for crystal structure and phase analysis.
• Rietveld refinement for detailed structural parameters.
• Raman spectroscopy to study vibrational modes.
• Photoluminescence spectroscopy to analyze emission properties under UV excitation.

Main Results:

• Tetragonal CaMoO4 structure confirmed, with co-existing cubic Er2O3 in doped samples.
• Rietveld refinement provided unit-cell dimensions, phase concentrations, and atomic coordinates.
• Raman spectra indicated masking of Er2O3 peaks by CaMoO4 vibrational modes.
• Er-doped CaMoO4 showed strong green emission under UV excitation.
• The 1 mol% Er2O3-CaMoO4 sample exhibited efficient down-conversion green emission at 531 nm and 552 nm with good color purity.

Conclusions:

• Solid-state synthesis is effective for producing Er2O3-CaMoO4 nanoparticles.
• The doping does not alter the primary crystal structure of CaMoO4 but introduces Er2O3 as a separate phase.
• Er-doping significantly enhances the luminescence properties of CaMoO4, particularly green emission.
• The 1 mol% Er2O3-CaMoO4 composition shows promise for applications in optical devices due to its efficient down-conversion luminescence.