Preparation, characterization, and photoluminescence properties of Tb 3+-, Ce3+-, and Ce3+/Tb3+-activated RE2Si4N6C (RE = Lu, Y, and Gd) phosphors

Photoluminescence properties of Tb3+ and Ce3+ singly doped and Ce3+/Tb3+-codoped RE2Si4N6C (RE = Lu, Y, and Gd) phosphors were investigated. Tb3+ shows similar luminescence properties in RE2Si4N6C (RE = Lu, Y, and Gd) host lattices and emits bright green light under UV excitation around 300 nrn. The luminescence properties of Ce3+ in RE2Si4N6C host lattices are influenced by the size of the RE3+ ions (Lu2Si4N6C and Y2Si4N6C vs Gd2Si4N6C). Both Ce3+-activated Lu2Si4N6C and Y2Si4N6C phosphors exhibit a broad band emission in the wavelength range of 450-750 nm with peak center at about 540 am, while Ce3+-activated Gd2Si4N6C 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 Ce3+ on the two crystallographic sites in Gd2S4N6C as compared to the Y and Lu compounds. In Ce3+/Tb3+-codoped RE2Si4N6C (RE = Lu,Y, and Gd) phosphors, it is observed that energy transfer takes place from Ce3+ to Tb3+ in Ce3+/Tb3+-codoped Lu2Si4N6C and Y2Si4N6C but in the reversed direction from Tb3+ to Ce3+ in Ce3+/Tb3+-codoped Gd2Si4N6C, depending on the position of the 5d level of Ce3+ versus the 5D(4) level of Tb3+. The potential applications of these phosphors are pointed out.