Layered Ceramic Phosphors Based on CaAlSiN₃:Eu and YAG:Ce for White Light‐Emitting Diodes

Abstract

To develop warm‐white light‐emitting diodes via conversion phosphors, blue light‐emitting diodes are generally combined with mixtures of green and red‐emitting phosphor powders. Generally, the phosphors are provided by resin embedded particle dispersions. Such resin‐based solutions cause several drawbacks with respect to LED lifetime and quality. Therefore, it has been investigated whether the red‐emitting nitride phosphor CaAlSiN3:Eu and the green‐emitting oxidic phosphor YAG:Ce can be cofired to layered ceramic composites. The shrinkage behavior and the composition of the interface in dependence of sintering temperature and the effect of interdiffusion processes at the interface on the luminescence properties were investigated. The formation of secondary phases at the interface in the cofired structures was found to limit the phosphor functionality for the nitride‐based CaAlSiN3:Eu in such composite ceramics. To counteract this, sacrificial interlayers were introduced to produce multilayered ceramics comprising CaAlSiN3:Eu and YAG:Ce for LED lighting applications. It is shown for the first time, that it is possible to sinter layered CaAlSiN3:Eu and YAG:Ce composite ceramics in a pressureless process at moderate sintering temperatures if one uses thin‐film passivated interfaces to reduce luminescence‐disturbing diffusion phenomena. These results demonstrate that diffusion barriers can be suitable means to obtain layered ceramic composites comprising CaAlSiN3:Eu and YAG:Ce in a pressureless sintering process with good optical properties.

A Thermally Robust La3Si6N11:Ce‐in‐Glass Film for High‐Brightness Blue‐Laser‐Driven Solid State Lighting

“…prepared a white‐emitting AlN:Ce ceramic with a high thermal conductivity, which is suitable for UV laser–driven high‐power lighting . Despite these efforts, most nitride phosphors can hardly be sintered to dense ceramics with acceptable optical properties due to their intrinsic low diffusion rate . By contrast, PiGs possess competitive advantages in easy fabrication and great versatility for various phosphors, and they have been widely utilized in white LEDs .…”

Improvement of self‐activated luminescence from introduced cation disorder in Sr6V2O11

“…Rare earth ion (RE)‐ or self‐activated phosphors have been widely investigated in engineering applications and basic sciences . Self‐activated phosphors present some advantages such as broad emission band, RE free, low sintering temperature, environment‐friendly (sintering in air), low cost, etc.…”

Dual color tuning in Ce3+‐doped oxyfluoride ceramic phosphor plate for white LED application

“…Nowadays, several works on the fabrication of ceramic phosphor such as LuAG/YAG:Ce 3+ and CASN:Eu 2+ have been reported, which use blue light as excitation source . To our knowledge, UV excitation in oxyfluoride ceramic phosphor plate has not been investigated yet.…”