Zinc oxide (ZnO) ceramics was coupled and reacted with alpha aluminum oxide (α-Al2O3) ceramics at 1200oC for 24 h. SEM observation and energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of diffusion layer of 10 μm thickness on the α-Al2O3 side of interface between ZnO and α-Al2O3. The diffusion layer is considered to consist of a ZnAl2O4, from the result of XRD. The cathodoluminescence of the diffusion layer was compared with that of zinc aluminate (ZnAl2O4) ceramics synthesized by conventional solid state reaction method. The single phase ZnAl2O4 showed weak emission peaked at 4.6 eV. On the other hand, the diffusion layer showed intense emission peaked at 3.75 eV. The ZnAl2O4 on the α-Al2O3 side of the interface synthesized by coupling of ZnO and α-Al2O3 is considered to be a excellent material as an ultraviolet light emitter.