Synthesis And Characterization Of Eu~(3+)-Doped Transparent Glass-Ceramics Containing Nanocrystalline Sr~(Ⅱ)Nb~(Ⅳ)O_3

摘要

The glass-ceramics containing a rarely achievable nanocrystalline Sr~(Ⅱ)Nb~(Ⅳ)O_3 phase in the 53.75SiO_2-18.25K_2O-9Bi_2O_3-9SrO-9Nb_2O_5-0.5CeO_2-0.5Eu_2O_3 (mol%) glass system were prepared by the melt-quench technique followed by a two-stage controlled heat treatment. The unusual oxidation state of Nb in Sr~(Ⅱ)Nb~(Ⅳ)O_3 crystal is 4+ and upon heat treatment of the samples at lower temperature of 500℃ for several hours, the glass composition and chemical environment around Nb ions played a key role for the formation of Sr~(Ⅱ)Nb~(Ⅳ)O_3 in the glass-ceramics. The microstructure of the glass-ceramics was studied using TEM and FESEM. The TEM images advocate 10-40 nm crystallite size of Sr~(Ⅱ)Nb~(Ⅳ)O_3. FTIR study confirms that all the samples consist of SiO_4, BiO_3, BiO_6, and NbO_6 structural units. The refractive index at different wavelengths was found to vary in the range 1.7105-1.7905 and increase with increase in heat-treatment time. The luminescence spectra of Eu~(3+)-doped glass and glass-ceramics were recorded at 465 nm excitation wavelength and the luminescence intensity is found to be increased with heat-treatment time due to increase in crystal-Unity. The high intensity ratio of ~5D_0→~7F_2 to ~5D_0 →~7F_1, indicates that the Eu -doped nanocrystalline Sr_(Ⅱ)Nb_(Ⅳ)O_3 glass-ceramics are promising candidate materials as red-light source.