High Thermal Stability and Color Purity of Y₂SrAl₄SiO₁₂: Eu³⁺ Garnet-Variant-Structured Phosphor for Warm White Light LED-Lamp

Abstract

Red LEDs with a high color purity and high color rendering index are often used to compensate for the lack of red-light components in current white LEDs. Therefore, the new type of garnet-structured high color purity red phosphor Y2−xSrAl4SiO12: xEu3+ was synthesized by the solid-state method. The band gap structure of the host matrix was studied through the DFT calculation and found that the matrix belongs to a direct band gap structure with a band gap size of 4.535 ev. The phosphor exhibits a wide excitation spectrum under the monitoring of 710 nm. The strongest excitation wavelength is 393 nm, and it exhibits bright red light under the excitation of 393 nm, and the emission peak positions are located at 570 nm, 597 nm, 613 nm, 650 nm, 710 nm and 748 nm, respectively, which are attributed to the 5D0→7Fj of Eu3+ (j = 0–5) electronic transitions. In the crystal structure of Y2SrAl4SiO12, Eu3+ occupies a symmetry site. The compositional changes and thermal studies found favorable at 20% mol. At this concentration, the luminescence intensity gradually weakened due to the Eu3+ electric multi-level interaction. It is worth noting that the emission intensity of Y2SrAl4SiO12: 20%Eu3+ at 433 K can be maintained to 92% of that at 293 K. Finally, we combined it with the NUV chip and packaged it into a red LED with a color purity of up to 90% and a correlated color temperature of 1492 K. The high purity, low color temperature and thermal stability indicate that it has a place in LED applications.

Keywords

• garnet structure
• phosphors
• thermal stability
• high color purity