[1] Schubert E. F. and Kim J. K., Sci. 308, 1274 (2005).
[2] SONG Guo-hua, MIAO Jian-wen, XU Shu-wu and JI Xiangming,Journal of Optoelectronics Laser 21, 1785 (2010).(in Chinese)
[3] Kuo T. W., Liu W. R. and Chen T. M., Opt. Express 18, 8187(2010).
[4] Xia Y. J., Huang F. Q., Wang W. D., Wang Y. M., Yuan K.D., Liu M. L. and Shi J. L., Opt. Mater. 31, 311 (2008).
[5] QIU Kun, XU Suo-cheng, TIAN Hua, ZHENG Xi, LV Tianshuai,LU Qi-fei and WANG Da-jian, Optoelectronics Letters 7, 350 (2011).
[6] Zeuner M., Schmidt P. J. and Schnick W., Chem. Mater. 21,2467 (2009).
[7] Wei X. D., Cai L. Y., Lu F. C., Chen X. L., Chen X. Y. and Liu Q. L., Chin. Phys. B 18, 3555 (2009).
[8] Li Y. Q., Hirosaki N., Xie R. J., Takeda T. and Mitomo M.,Chem. Mater. 20, 6704 (2008).
[9] Meijerink A., Bachmann V., Ronda C., Oeckler O. and Schnick W., Chem. Mater. 21, 316 (2009).
[10] Toda K., Kawakami Y., Kousaka S., Ito Y., Komeno A.,Uematsu K. and Sato M., Ieice T. Electron. E89c, 1406(2006).
[11] Nakanishi T. and Tanabe S., Phys. Status Solidi. A 206, 919(2009).
[12] Yoon D. H., Park W. J., Jung M. K., Kang S. M. and Masaki T., J. Phys. Chem. Solids 69, 1505 (2008).
[13] Zhuang W. D., Deng C. Y., He D. W., Wang Y. S., Kang K.and Huang X. W., J. Rare Earths 22, 108 (2004).
[14] Lee G. H., Yoon C. and Kang S., J. Mater. Sci. 43, 6109(2008).
[15] Zhang X. Y., Cheng G., Liu Q. S., Cheng L. Q., Lu L. P., Sun H. Y., Wu Y. Q., Bai Z. H. and Qiu G. M., J. Rare Earths 28,526 (2010).
[16] Ma L., Wang D. J., Zhang H. M., Gu T. C. and Yuan Z. H.,Electrochem. Solid State Lett. 11, E1 (2008).