[1] M.J.Weber: J. Non-Cryst. Solids., 1990, 123, 208. [2] J.S.Wang, E.M.Vogel and E.Snitzer: Opt. Mater., 1994, 3,187. [3] J.McDougall, D.B.Hollis and J.P.Payne: Phys. Chem. Glasses,1996, 37, 254. [4] T.Komautsu and K.Shioya: J. Non-Cryst. Solids., 1997, 209,305. [5] Y.Ohishi, A.Mori, M.Yamada, H.Ono. Y.Nishida andK.Oikawa: Opt. Lett., 1998, 23, 274. [6] Z.Pan, S.H.Morgan, K.Dyer, A.Ueda and H.Liu: J. Appl. Pbys., 1996, 79, 8906. [7] A.A.Bahgat, E.E.Shaisha and A.I.Sabry: J. Mater. Sci., 1987. 22, 1323. [8] H.Jong, L.David, H.George, J.Sigel, M.A.Edgar andH.A.David: J. Am. Ceram. Soc., 1992, 75, 277. [9] M.Tatsumisago, T.Minami, Y.Kowada and H.Adachi: Phys.Chem. Glasses, 1994, 35, 89. [10] S.Neov, I.Gerasimova, V.Kozhukharov and M.Marinov: J.Mater. Sci., 1980, 15, 1153. [11] J.McDougall, D.Hollis and M.J.P. Payne: Phys. Chem.Glasses, 1996 37, 254. [12] R.N.Sinclair, A.C.Wright, B.Bachra, Y.B.Dimitriev,V.V.Dimitrov and M.G.Arnaudov: J. Non-Cryst. Solids.,1998, 232, 38. [13] R.Goring, H.Burger, H.Nass and B.Schnabel: Phys. Stat. So-lidi (a)., 1981, 68, 29. [14] K.Muruganandam and M.Seshasayee: J. Non-Cryst. Solids.,1997, 222, 131. [15] L.Hu and Z.Jiang: Phys. Chem. Glasses, 1996, 37, 19. [16] Y.Dimitriev and V.Dimitrov: J. Mater. Sci., 1979, 14, 723. [17] A.A.Bahgat, E.E.Shaisha and A.I.Sabry: J. Mater. Sci., 1987,22, 1323. [18] K.Shioya, T.Komatsu, H.G. Kim, R.Sato and K.Matusita: J.Non-Cryst. Solids., 1995, 189, 16. [19] T.Kosuge, Y.Benino, V.Dimitrov, R.Sato and T.Komatsu: J.Non-Cryst. Solids., 1998, 242, 154. [20] J.C.Sabadel, P.Armand, P.E.Lippens, D.C.Herreillat andE.Philippot: J. Non-Cryst. Solids., 1999, 244, 143. [21] Z.Pan and S.H.Morgan: J. Non-Cryst. Solids., 1997, 210, 130. [22] N.S.Hussain, K.Annapurna and S.Buddhudu: Phys. Chem.Glasses, 1997, 38, 51. [23] K.Annapurna, R.N.Dwivedi and S.Buddhudu: Opt. Mater.,2000, 13, 381. [24] Y.Ding, S.Jiang, B.C.Hwang, T.Luo, N.Peygharnbarian,Y.Himei, T.Ito and Y.Miura: Opt. Mater., 2000, 15, 381. [25] A.Hruby and Czech: J. Phys., 1972, B22, 1187. [26] A.Feltz: Amorphous Inorganic Materials and Glasses, NewYork, 1993, 54. [27] M.Imaoka and T.Yamazaki: J. Ceram. Soc. Jpn., 1968, 76,160. [28] J.S.Wang, E.M.Vogel and E.Snitzer: Opt. Mater., 1994, 3,187. [29] Z.Pan and S.H.Morgan: J. Non-Cryst. Solids., 1997, 210, 130. [30] T.Komatsu, H.Tawarayama. H.Mohri and K.Matusita: J. Non-Cryst. Solids, 1991, 135, 105. [31] Y.Himei, A.Osaka, T.Nanba and Y.Miura: J. Non-Cryst.Solids, 1994, 177, 164. [32] T.Yoko, K.Kamiya, K.Tanaka, H.Yamada and S.Sakka: Yogyo-Kyokai-Shi., 1989, 97(3) , 289.l |