Sm³⁺ doped calcium orthovanadate Ca₃(VO₄)₂ - A spectral study

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Development of efficient phosphors is crucial for advanced lighting technologies, particularly for phosphor-converted white light-emitting diodes (wLEDs).
• Vanadate-based materials doped with rare-earth ions are actively researched for their luminescent properties.

Purpose of the Study:

• To synthesize and characterize Sm³⁺-doped calcium vanadate (Ca_3-x(VO₄)₂:Sm_x) phosphors.
• To evaluate their potential as orange-emitting components for wLED applications.

Main Methods:

• Citrate-based sol-gel method for phosphor synthesis.
• Characterization using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), diffuse reflectance, and photoluminescence spectroscopy.
• Band gap energy calculation using the Kubelka-Munk function.

Main Results:

• Successful synthesis of Sm³⁺-doped Ca₃(VO₄)₂ phosphors with varying Sm³⁺ concentrations (x = 0.005–0.095).
• Band gap energy determined to be 3.28 eV for Ca_2.95(VO₄)₂:Sm_0.05.
• Broadband excitation from VO₄ tetrahedra and narrow peaks from Sm³⁺ 4f-4f transitions observed.
• Characteristic orange emission peaks (564, 601, 648, 701 nm) upon 404 nm excitation.
• Optimal Sm³⁺ concentration found to be 0.05 mol, with a critical distance (R_c) of 19.1 Å.
• Emission quenching attributed to dipole-dipole interactions and cross-relaxation processes.
• CIE coordinates place the emission in the orange region, with pure orange color observed under 365 nm UV light.

Conclusions:

• Ca₃(VO₄)₂:Sm³⁺ phosphors demonstrate efficient orange luminescence.
• The synthesized phosphors are suitable candidates for the orange-emitting component in phosphor-converted wLEDs.
• Further investigation into optimizing synthesis and performance for wLED applications is warranted.