[1] [1] X. Wu, C. Zou, W. Wei, F. Sun, G. Guo, and Z. Han, Chin. Opt. Lett. 8, 709 (2010).

[2] [2] Q. Wei, Z. Ren, Z. He, and Z. Niu, Chin. Opt. Lett. 7, 52 (2009).

[3] [3] X. Y. He, R. P. Jia, C. F. Ouyang, X. Wang, and J. H. Yang, Nano: Brife Reports and Reviews 2, 383 (2007).

[4] [4] J. C. Sancoski, L. S. Cavalcante, M. R. Joya, J. A.Varela, P. S. Pizani, and E. Longo, Chem. Eng. J. 140, 632 (2008).

[5] [5] L. S. Cavalcante, J. C. Sczancoski, V. C. Albarici, J. M. E. Matos, J. A. Varela, and E. Longo, Mater. Sci. Eng. B 150, 18 (2008).

[6] [6] M. Minowa, K. Itakura, S. Moriyama, and W. Ootani, Nuclear Instruments and Methods in Physics Research Section A 320, 500 (1992).

[7] [7] A. Phuruangrat, T. Thongtem, and S. Thongtem, J. Phys. Chem. Solids 70, 955 (2009).

[8] [8] I. Bavykina, G. Angloher, D. Hauff, M. Kiefer, F. Petricca, and F. Pr¨obst, Opt. Mater. 31, 1382 (2009).

[9] [9] V. B. Mikhailik, H. Kraus, D. Wahl, H. Ehrenberg, and M. S. Mykhaylyk, Nuclear Instruments and Methods in Physics Research Section A 562, 513 (2006).

[10] [10] Z. Li, J. Du, J. Zhang, T. Mu, Y. Gao, B. Han, and J. Chen, Mater. Lett. 59, 64 (2005).

[11] [11] D. A. Spassky, S. N. Ivanov, V. N. Kolobanov, V. V. Mikhailin, V. N. Zemskov, B. I. Zadneprovski, and L. I. Potkin, Radiat. Meas. 38, 607 (2004).

[12] [12] T. Thongtema, A. Phuruangrat, and S. Thongtem, J. Ceram. Process. Res. 9, 189 (2008).

[13] [13] L. S. Cavalcante, J. C. Sczancoski, R. L. Tranquilin, M. R. Joya, P. S. Pizani, J. A.Varela, and E. Longo, J. Phys. Chem. Solids 69, 2674 (2008).

[14] [14] P. Yang, G. Q. Yao, and J. H. Lin, Inorg. Chem. Commun. 7, 389 (2004).

[15] [15] J. H. Ryu, B. G. Choi, J. W. Yoon, K. B. Shim, K. Machi, and K. Hamada, J. Lumin. 124, 67 (2007).

[16] [16] Committee on Powder Diffraction Standard, “Powder diffraction File JCPDS Int. Centre Diffraction Data”, PA 19073-3273, USA (2001).

[17] [17] J. C. Sczancoski, M. D. R. Bomio, L. S. Cavalcante, M. R. Joya, P. S. Pizani, J. A. Varela, E. Longo, M. S. Li, and J. A. Andr′es, J. Phys. Chem. C 113, 5812 (2009).

[18] [18] G. M. Clark and W. P. Doyle, Spectrochimica Acta 22, 1441 (1966).

[19] [19] Z. C. Ling, H. R. Xia, D. R. Ran, F. Q. Liu, S. Q. Sun, J. D. Fan, H. J. Zhang, J. Y. Wang, and L. L. Yu, Chem. Phys. Lett. 426, 85 (2006).

[20] [20] J. A. Gadsden, IR Spectra of Minerals and Related Inorganic Compounds (Butterworths, London,1975).

[21] [21] X. Wu, J. Du, H. Li, M. Zhang, B. Xi, H. Fan, Y. Zhu, and Y. Qian, J. Solid State Chem. 180, 3288 (2007).

[22] [22] J. Yang, C. Lu, H. Su, J. Ma, H. Cheng, and L. Qi, Nanotechnology 19, 035608 (2008).

[23] [23] D. L. Wood and J. Tauc, Phys. Rev. B 5, 3144 (1972).

[24] [24] R. Lacomba-Perales, J. Ruiz-Fuertes, D. Errandonea, D. Martinez-Garcfa, and A. Segura, Eur. Phys. Lett. 83, 37002 (2008).

[25] [25] R. M. Hazen, L. W. Finger, and J. W. E. Mariathasan, J. Phys. Chem. Solids 46, 253 (1985).