Structural and Photoluminescence Properties of Ce3+- and Tb3+-Activated Lu-α-Sialon

Abstract

The crystal structure and photoluminescence properties of undoped and Ce 3+ - or Tb 3+ -doped Lu-α-Sialon are reported. Lu-α-Sialon with the composition of Lu 0.367 Si 9.9 Al 2.1 ON 15 crystallizes in a trigonal system with a = 7.8013(1) A, c = 5.6827(1) A, in the space group P31c. The Lu 3+ ion is accommodated at the interstice site at 2b and directly connected by seven (N, O) atoms with an average bond length of 2.624 A. The incorporation of large Ce 3+ and Tb 3+ ions on small Lu 3+ site results in the expansion of the unit cell as expected but keeping the average Lu Ln -(N, O) (Ln = Ce, Tb) distances nearly constant with slight distortion in the lattices. The optical band gap of Lu-α-Sialon is about 5.25 eV determined by the diffused reflection spectrum. Lu-α-Sialon:Ce 3+ (2 mol%) exhibits efficiently greenish-blue emission at about 486 nm under near-ultraviolet (UV) excitation originating from the 5d→4f 1 5d 0 transition of Ce 3+ . Lu-α-Sialon:Ce 3+ is a potential candidate phosphor for white UV-LED applications due to its high quantum efficiency and excellent thermal stability. Lu-α-Sialon:Tb 3+ (2 mol%) emits strong mixed blue and green light in equivalent due to the transitions of 5 D 3 → 7 F J and 5 D 4 → 7 F J of Tb 3+ .