Layered Structure Produced Nonconcentration Quenching in a Novel Eu³⁺-Doped Phosphor

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence and Phosphor Technology

Background:

• Energy migration is typically linked to concentration quenching in luminescence materials.
• The established understanding suggests that increasing dopant concentration can lead to luminescence quenching.
• Exceptions to this rule are crucial for developing advanced luminescent materials.

Purpose of the Study:

• To investigate the luminescence properties of novel Europium-doped Barium Gadolinium Titanium Oxide (Ba₆Gd₂Ti₄O₁₇:Eu³⁺) phosphors.
• To explore the phenomenon of concentration quenching in these phosphors.
• To evaluate the potential of these phosphors for lighting applications, including red light emission and warm white light generation.

Main Methods:

• Synthesis of a series of Ba₆Gd_{2(1- x)}Ti₄O₁₇: xEu³⁺ phosphors with varying Europium concentrations (x = 0.1–0.9).
• Detailed investigation of crystal structure and luminescence properties.
• Fabrication of a near-UV light-emitting diode (LED) chip incorporating the synthesized phosphors with other phosphors (YGAB:Tb³⁺ and BAM:Eu²⁺) to generate warm white light.

Main Results:

• No concentration quenching was observed in the synthesized Ba₆Gd_{2(1- x)}Ti₄O₁₇: xEu³⁺ phosphors, even at high Europium doping levels.
• The absence of concentration quenching is attributed to the dimensional restriction of energy migration within the crystal lattice.
• The highly Eu³⁺-doped sample (x=0.9) efficiently converts near-UV excitation to red light with high color purity (94.4%) and Commission Internationale de l'Eclairage (CIE) coordinates (0.64, 0.36).
• Warm white light with CIE coordinates (0.39, 0.39), a correlated color temperature of 3756 K, and a color rendering index of 82.2 was successfully generated in an LED device.

Conclusions:

• The Ba₆Gd₂Ti₄O₁₇:Eu³⁺ phosphor system represents an exception to the typical concentration quenching phenomenon.
• The dimensional restriction of energy migration is key to achieving high brightness at high Eu³⁺ concentrations.
• These phosphors show significant promise for applications in solid-state lighting, particularly for generating efficient red light and high-quality warm white light.