Preparation And Characterization Of Rare Earth Doped-ZnO-Al₂O₃-SiO₂ System Transparent Glass-Ceramics

This dissertation presented that the origin and development.The compositions, structure and processes of glass-ceramics were discussed.The synthetic methods and applications of glass-ceramics were outlined,and the developing trend of ZnO-Al₂O₃-SiO₂(ZAS) was forecasted.Transparent ZnO-Al₂O₃-SiO₂(ZAS) system glass-ceramics using TiO₂ as nucleating agent were prepared by the melting method and crystal technique.The crystallization heat-treated schedules were based on DTA results.The compositions and structure of crystal phases were determined on the base of XRD results.The transparent ZAS glass-ceramics with main crystal phase- ZnAl₂O₄ and minor crystal phase- SiO₂ solid solutions,Zn₂SiO₄,SiO₂ were obtained after ZAS system glasses with good crystallization ability were nucleated at 670℃and crystallized at 740～810℃.It was shown that the little change to the compositions influenced the crystal phases unmarkedly.The element composition of the sample were analyzed by determining the nature by EDX.The optical transmittances of the ZAS glass-ceramics were measured by spectrophotometer.The influences of crystallization heat-treated schedules to the optical transmittance were discussed.Transparent ZnO-Al₂O₃-SiO₂(ZAS) system glass-ceramics Nd₂O₃-doped using TiO₂ as nucleating agent were prepared by the melting method and crystal technique. The crystallization heat-treated schedules were based on DTA results.The compositions and structure of crystal phases were determined on the base of XRD results.The transparent ZAS glass-ceramics with main crystal phase- cubic gahnite ZnAl₂O₄ and minor crystal phase-tetrahedronβ-SiO₂ solid solutions were obtained after ZAS system glasses with good crystallization ability were nucleated at 660℃and crystallized at 740～880℃.The unique crystal phase-gahnite was precipitated below 1050℃,tetrahedronβ-SiO₂ solid solutions begin to precipitate at1050℃and become to the main crystal phase at 1050℃,and at the same time,gahnite became to the minor crystal phase and minor crystal phases-Zn₂SiO₄ was precipitated The lattice parameter of cubic gahnite calculated by XRD results isα=0.8087nm(±0.0012).The optical transmittances of the glass-ceramics were measured by spectrophotometer. The influences of crystallization heat-treated schedules to the optical transmittance were discussed.The microstructure of the transparent ZAS system glass-ceramics was analyzed by SEM,The element composition of the sample were analyzed by determining the nature by EDX.The fluorescence spectra of the base glass and glass-ceramic heat-treated at different schedules were measured.The influences of crystal phase compositions and microstructure were discussed.Phase compositions and grain size of glass-ceramics were found to affect their fluorescent characteristics considerably.Three main fluorescence bands centering at about 885nm,1064nm and 1337nm were observed,which were correspondent to the transitions of ⁴F_3/2→⁴I_9/2, ⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_13/2,respectively.The optical transmittances of the ZAS glass-ceramics decreased with the Nd³⁺doped after comparing sample 1-1# without Nd³⁺- doped and 2-2# with Nd³⁺- doped. Transparent ZnO-Al₂O₃-SiO₂(ZAS) system glass-ceramics NdF₃-doped using TiO₂ as nucleating agent were prepared by the melting method and crystal technique. The crystallization heat-treated schedules were based on DTA results.The compositions and structure of crystal phases were determined on the base of XRD results.The transparent ZAS glass-ceramics with main crystal phase- cubic gahnite ZnAl₂O₄ and minor crystal phase-tetrahedronβ-SiO₂ solid solutions and Zn₂SiO₄ were obtained after ZAS system glasses with good crystallization ability were nucleated at 670℃for 1h and crystallized at 730℃for 1h.The crystal phase- ZnF₂ was precipitated with time of crystallization and nucleation increasing.The unique main crystal phase-tetrahedronβ-SiO₂ solid solutions were precipitated and gahnite became to the minor crystal phase in the transparent glass-ceramics when nucleation temperature reached 1040℃.The element composition of the sample were analyzed by determining the nature by EDX.The short-range structure of the transparent glass-ceramics samples was researched by XPS.The fluorescence spectra of the base glass and glass-ceramic heat-treated at different schedules were measured.Three main fluorescence bands centering at about 881nm,1063nm and 1334nm were observed, which were correspondent to the transitions of ⁴F_3/2→⁴I_9/2,⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_13/2, respectively.The effectively induced cross sectionσ_in of Nd³⁺ ions locating in crystal phase-ZnF₂ of the transparent glass-ceramics sample at 1065nm advanced than in base glass.The fluorescence spectra and the optical transmittances of the Nd₂O₃-doped 2-2# ZAS transparent glass-ceramics and NdF₃-doped 3-3# ZAS transparent glass-ceramics respectively with the same nucleating agent were compared.The optical transmittances decreased and the illuminant intensity improved when the minor crystal phase-ZnF₂ was precipitated in NdF₃-doped 3-3# ZAS transparent glass-ceramics.Transparent ZnO-Al₂O₃-SiO₂(ZAS) system glass-ceramics NdF₃-doped using CaF₂ as nucleating agent were prepared by the melting method and crystal technique. The crystallization heat-treated schedules were based on DTA results.The compositions and structure of crystal phases were determined on the base of XRD results.The transparent ZAS glass-ceramics with main crystal phase- SiO₂ solid solutions and minor crystal phase-Zn₂SiO₄,CaF₂ and the transparent ZAS glass-ceramics with main crystal phase- SiO₂ solid solutions minor crystal phaseZn₂SiO₄, ZnAl₂O₄ and CaF₂ were obtained after ZAS system base glasses were nucleated at 670℃and crystallized at 740℃-800℃.The element composition of the sample were analyzed by determining the nature by EDX.The short-range structure of the transparent glass-ceramics samples was researched by XPS.The fluorescence spectra of the base glass and glass-ceramic heat-treated at different schedules were measured.Three main fluorescence bands centering at about 896nm,1064nm and 1329nm were observed,which were correspondent to the transitions of ⁴F_3/2→⁴I_9/2, ⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_13/2,respectively.The effectively induced cross sectionσ_in of Nd³⁺ ions locating in crystal phase-CaF₂ of the transparent glass-ceramics sample at 1064nm advanced than in base glass.The fluorescence spectra and the optical transmittances of the NdF₃-doped 3-3# ZAS transparent glass-ceramics NdF₃-doped using TiO₂ as nucleating agent and NdF₃-doped 4-3# ZAS transparent glass-ceramics NdF₃-doped using CaF₂ as nucleating agent respectively with the same nucleating agent were compared.The optical transmittances and the illuminant intensity improved of 4-3# ZAS transparent glass-ceramics NdF₃-doped using CaF₂ as nucleating agent.The microstructure of the transparent ZAS glass-ceramic samples NdF₃-doped using CaF₂ as nucleating agentwas analyzed by SEM,and the microstructure parameters were obtained by means of automatic image analysis technique.The microstructure was studied by stereology principles and method,and the relationship between the microstructure and the optical properties was explored.The optical transmittance decreased with the increasing of the three-dimensional sphere diameters and the mean specific area of grains per volume.The optical transmittance increased with the enhancing of the mean three-dimensional free distance of grain boundaries and the mean specific area of single grain.The microstructure of ZAS transparent glass-ceramics was described by using fractal theory,it was proved that transparent ZnO-Al₂O₃-SiO₂(ZAS) system glass-ceramics are of fractal characterizations.