We present our achievement which is a ceramic plate phosphorable to produce white light when directly combined with commercially available blue light emitting diodes. The ceramic phase structure is that the Al₂O₃ particle is uniformly distributed in the Ce:YAG matrix. The Al₂O₃-Ce:YAG ceramic phosphor has a better luminous efficacy than the transparent Ce:YAG ceramic phosphor under the same test condition. The Al₂O₃ particle plays an important role in promoting the luminous efficacy. The Al₂O₃ particle changes the propagation of the light in ceramic, and it reduces the total internal reflection. That is why the composite phase ceramic phosphor improves extraction efficiency of light.

The Cr/Ce‐doped YAG transparent ceramic was fabricated by the solid‐state reaction in vacuum. The Cr/Ce‐doped YAG ceramic phosphor effectively complement the red spectral component and improve the color rendering performance when excited by blue light that is due to the effective energy transfer between Cr3+ ion and Ce3+ ion. However, the energy transfer from Ce3+ to Cr3+ ion leads to energy loss and therefore the luminous efficacy of the WLED which is composed of blue LED chip and the Cr/Ce‐doped YAG ceramic phosphor decreases. The composite phase structure of ceramic phosphor is designed for improving the extraction efficacy and increasing the luminous efficacy by breaking the total internal reflection (TIR) at the interface between air and ceramic.

No abstract