Spinel-Based ZnAl₂O₄: 0.5%Cr³⁺ Red Phosphor Ceramics for WLED

To address the issue of the lack of red light in traditional Ce³⁺: YAG-encapsulated blue LED white light systems, we utilized spark plasma sintering (SPS) to prepare spinel-based Cr³⁺-doped red phosphor ceramics. Through phase and spectral analysis, the SPS-sintered ZnAl₂O₄: 0.5%Cr³⁺ phosphor ceramic exhibits good density, and Cr³⁺ is incorporated into [AlO₆] octahedra as a red emitting center. We analyzed the reasons behind the narrow-band emission and millisecond-level lifetime of ZAO: 0.5%Cr³⁺, attributing it to the four-quadrupole interaction mechanism as determined through concentration quenching modeling. Additionally, we evaluated the thermal conductivity and thermal quenching performance of the ceramic. The weak electron-phonon coupling (EPC) effects and emission from antisite defects at 699 nm provide positive assistance in thermal quenching. At a high temperature of 150 °C, the thermal conductivity reaches up to 14 W·m^-1·K^-1, and the 687 nm PL intensity is maintained at around 70% of room temperature. Furthermore, the internal quantum efficiency (IQE) of ZAO: 0.5%Cr³⁺ phosphor ceramic can reach 78%. When encapsulated with Ce³⁺: YAG for a 450 nm blue LED, it compensates for the lack of red light, adjusts the color temperature, and improves the color rendering index (R9). This provides valuable insights for the study of white light emitting diodes (WLEDs).