The effect of Al-O substitution for Si-N on the luminescence properties of YAG:Ce phosphor

The present paper describes the effect of various Si-N substitution degree on the crystal structure and optical properties of yellow YAG:Ce phosphor commonly used with combination of InGaN in white LEDs. It has been found that the course of silicon/nitrogen YAG:Ce garnet doping as well as formation of the liquid phase and its chemical composition controlled formation of the side phase besides YAG:Ce. Substitution of Al-O for Si-N chemical bonds according to the general formula Y _2.94Ce _0.06Al _(5-x)Si _xO _(12-x)N _x was confirmed by changes of the unit cell parameter and formation of the Si-N bonds as detected by FT-IR studies. Formation of the nitrogen ligand in cerium arrangement resulted in a red shift in emission spectrum of trivalent cerium if nominal x value was in the range of 0.2-0.3. Above x=0.3 only decrease of emission intensity was observed because of the secondary phase precipitation but further solution of Si-N in YAG:Ce crystal lattice cannot be excluded.