Novel Garnet-Structure Ca2GdZr2(AlO4)3:Ce3+ Phosphor and Its Structural Tuning of Optical Properties

Aluminate garnet phosphors Ca2GdZr2(AlO4)(3):Ce3+ (CGZA:Ce3+) for solid-state white lighting sources are reported. The crystal structure and Mulliken bonding population of the CGZA:Ce3+ have been analyzed. The larger 5d (D-2) barycenter shift epsilon(c) and smaller phenomenological parameter 10D(q) of Ce3+ in CGZA are related to the larger covalent character of Ce-O. The tuning spectral properties of the Ce3+-doped CGZA-based isostructural phosphors are presented. The splitting of cubic crystal field energy level E-2(g) in Ca2REZr2(AlO4)(3):Ce3+ (CREZA:Ce3+) (RE = Lu, Y, and Gd) increases as the radius of RE3+ increases, and the splitting of E-2(g) may dominate the difference of spectroscopic red-shift D(A) in CREZA:Ce3+. The splitting of the E-2(8) in CaGd2ZrSc(AlO4)(3):Ce3+ (CGZSA:Ce3+) phosphors increases seemly due to the decreasing of the covalent character of Ce-O. Thermal quenching properties of Ce3+-doped CGZA-based isostructural phosphors are also presented and analyzed. For CREZA:Ce3+ phosphors, the increasing of the radius of RE3+ results in an enhancement of thermal quenching. The quenching of CGZSA:Ce3+ is obviously stronger mainly due to the smaller energy difference between the lowest Sd excited state and 4f ground state.