Preparation, Characterization, and Photoluminescence Properties of Tb³⁺-, Ce³⁺-, and Ce³⁺/Tb³⁺-Activated RE₂Si₄N₆C (RE = Lu, Y, and Gd) Phosphors

Photoluminescence properties of Tb 3+ and Ce 3+ singly doped and Ce 3+ /Tb 3+ -codoped RE 2 Si 4 N 6 C (RE = Lu, Y, and Gd) phosphors were investigated. Tb 3+ shows similar luminescence properties in RE 2 Si 4 N 6 C (RE = Lu, Y, and Gd) host lattices and emits bright green light under UV excitation around 300 nm. The luminescence properties of Ce 3+ in RE 2 Si 4 N 6 C host lattices are influenced by the size of the RE 3+ ions (Lu 2 Si 4 N 6 C and Y 2 Si 4 N 6 C vs Gd 2 Si 4 N 6 C). Both Ce 3+ -activated Lu 2 Si 4 N 6 C and Y 2 Si 4 N 6 C phosphors exhibit a broad band emission in the wavelength range of 450−750 nm with peak center at about 540 nm, while Ce 3+ -activated Gd 2 Si 4 N 6 C shows a broad emission band in the wavelength range of 500−800 nm with peak center at about 610 nm. This difference is ascribed to the different site occupations of Ce 3+ on the two crystallographic sites in Gd 2 Si 4 N 6 C as compared to the Y and Lu compounds. In Ce 3+ /Tb 3+ -codoped RE 2 Si 4 N 6 C (RE = Lu, Y, and Gd) phosphors, it is observed that energy transfer takes place from Ce 3+ to Tb 3+ in Ce 3+ /Tb 3+ -codoped Lu 2 Si 4 N 6 C and Y 2 Si 4 N 6 C but in the reversed direction from Tb 3+ to Ce 3+ in Ce 3+ /Tb 3+ -codoped Gd 2 Si 4 N 6 C, depending on the position of the 5d level of Ce 3+ versus the 5 D 4 level of Tb 3+ . The potential applications of these phosphors are pointed out.