Cold sintered Ce3+:Lu3Al5O12-Mn4+:K2SiF6-Y3+:CaF2 transparent ceramic phosphors for high color rendering white LEDs/LDs

Abstract

Transparent ceramics with ultra-wide emission spectra are widely considered as the next-generation color converters for high color rendering white light emitting diodes (LEDs) and laser diodes (LDs). Herein, a novel Ce³⁺:Lu₃Al₅O₁₂-Mn⁴⁺:K₂SiF₆-Y³⁺:CaF₂ transparent ceramic phosphor was prepared by the cold sintering method. The samples sintered at 250 °C and 175 MPa exhibit considerable visible transmittance (about 43%) and uniform grain distribution with no interfacial reaction. When excited at 460 nm, the samples exhibit both broad green emission bands (Ce³⁺: 5d → 4 f) and sharp red peaks (Mn⁴⁺: ²E_g → ⁴A_2g), possessing over 90% internal quantum efficiencies and quite small thermal quenching. The assembled white LED exhibits luminous efficiency (LE) of 96.4 lm/W and color rendering index (CRI) of 94.5, while the reflection-type white LD shows LE of 207.4 lm/W and CRI of 85.0. It demonstrates that the Ce³⁺:Lu₃Al₅O₁₂-Mn⁴⁺:K₂SiF₆-Y³⁺:CaF₂ transparent ceramics exhibit great potential in the high-power LED/LD lighting.