Eu³⁺ doped CaWO₄ nanophosphor for high sensitivity optical thermometry

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Calcium tungstate (CaWO4) phosphors are widely studied for luminescence applications.
• Europium (Eu3+) doping is a common strategy to achieve specific emission properties.
• Developing efficient and stable phosphors for temperature sensing remains an active research area.

Purpose of the Study:

• To synthesize Eu3+ doped CaWO4 nanophosphors using a hydrothermal method.
• To investigate the structural, morphological, and luminescent properties of the synthesized materials.
• To evaluate their potential for optical thermometry applications.

Main Methods:

• Hydrothermal synthesis with varying sodium citrate concentrations.
• X-ray Diffraction (XRD) for structural analysis.
• Field Emission Scanning Electron Microscopy (FE-SEM) for morphology.
• Luminescence spectroscopy to study temperature-dependent properties.

Main Results:

• Scheelite structure CaWO4: Eu3+ nanophosphors were successfully synthesized.
• Particle size decreased to nanoscale (average 90 nm) with increasing sodium citrate.
• Distinct thermal quenching behaviors of Eu3+ and WO4(2-) luminescence were observed.
• Maximum relative sensitivity of 4.3% K-1 was achieved at 303 K for 90 nm particles.
• Luminescence color shifted from blue to pink-red with increasing temperature.

Conclusions:

• CaWO4: Eu3+ nanophosphors exhibit temperature-dependent luminescence suitable for optical thermometry.
• Particle size significantly influences sensitivity, with smaller nanoparticles showing enhanced performance.
• The observed color change and fluorescence intensity ratio (FIR) provide dual mechanisms for temperature sensing.