[3] Li X, Li Q, Wang J Y. J. Lumin., 2007, 124: 351.

[4] Wang C N, Zhao J B, Li Y, et al. J. Rare Earth, 2009, 27(6): 879.

[5] Kang Y C, Roh H S, Park S B, et al. J. Eur. Ceram. Soc., 2002, 22: 1661.

[6] Cho J Y, Ko K Y, Do Y R. Thin Solid Films, 2007, 515: 3373.

[7] Sung J M, Lin S E, Wei W C J. J. Eur. Ceram. Soc., 2007, 27: 2605.

[8] Dikovska A O G, Atanasov P A, Dimitrov I G, et al. Appl. Surf. Sci., 2006, 252: 4569.

[9] Dikovska A O G, Atanasov P A, Castro M J D, et al. Thin Solid Films, 2006, 500: 336.

[10] Zhang J, Wang S W, An L Q, et al. J. Lumin., 2007, 122-123: 8.

[11] Li Y H, Zhang Y M, Hong G Y, et al. J. Rare Earth, 2008, 26(3): 450.

[12] Guo H, Qiao Y M. Opt. Mater., 2009, 31: 583.

[13] Qiao Y M, Guo H. J. Rare Earth, 2009, 27(3): 406.

[14] De G J H, Qin W P, Zhang J S. J. Lumin., 2006, 119-120: 258.