Highly efficient rare-earth free vanadate phosphors for WLEDs.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Vanadate phosphors are crucial for solid-state lighting.
• Tantalum doping can tune phosphor properties.

Purpose of the Study:

• Synthesize and characterize yellow-green emitting Ca5Mg4(VO4)6 (CMV) phosphors doped with Ta5+.
• Investigate the effect of Ta5+ concentration on luminescence properties.
• Evaluate the potential of these phosphors for white light-emitting diode (WLED) applications.

Main Methods:

• Solid-state reaction method for phosphor synthesis.
• X-ray diffraction (XRD) and Rietveld refinement for structural analysis.
• Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy for optical characterization.
• Measurement of luminescence lifetime, quantum efficiency, and color coordinates.

Main Results:

• Single-phase CMV:Ta5+ phosphors with a garnet structure were successfully synthesized.
• The phosphors exhibit bright yellow-green emission peaking at 544 nm, suitable for 365 nm LED chips.
• Optimized doping (0.5% Ta5+) enhanced luminescence intensity by 26.31% and quantum efficiency by 15.98%.
• WLED devices fabricated with CMV:0.5%Ta5+ showed excellent color temperature (4083 K) and CIE coordinates (0.3677, 0.3409).

Conclusions:

• Ta5+ doping effectively enhances the luminescence properties of CMV phosphors.
• The synthesized CMV:Ta5+ phosphor is a promising candidate for yellow-green emission in solid-state lighting.
• The improved performance is attributed to Ta5+ induced distortion of the [VO4]3- tetrahedron.