Preparation And Optical Properties Of Doped ZnO-MgO-Al₂O₃-SiO₂ System Glass-ceramics

In the present thesis,transparent glass-ceramics with spinel phase as the main crystalline phase were prepared through heat-treatment of ZnO-Mg O-Al₂O₃-SiO₂system matrix glass via melt quenching method,and the effects of heat treatment process parameters on the nucleation and growth of microcrystals,organization and optical properties of glass-ceramics were investigated.The results show that the heat treatment time affects the degree of crystallization of the spinel phase in the glass-ceramics,resulting in more dopant ions accumulating in the spinel phase,which in turn affects the optical properties of the glass-ceramics.Transparent glass-ceramics of the Co²⁺-doped ZMAS system were prepared,and the heat treatment regime of the basic glass was developed from the results of differential thermal analysis.Based on the X-ray diffraction results,it was determined that the main crystalline phase of glass-ceramics was ZnAl₂O₄/Mg Al₂O₄,and the composition of the glass-ceramics did not change significantly with the increase of the crystallization treatment time,and the crystallinity and the average grain size of spinel showed a trend of first increasing and then decreasing.The optical properties of glass-ceramics and the doping mode of Co²⁺ions in spinel were analyzed by testing the absorption spectra and emission spectra of the samples,and it was found that the broad absorption band of ⁴T₁（⁴F）→⁴A₂（⁴F）transitions and the emission peak of ⁴T₁（⁴P）→⁴A₂（⁴F）transitions of tetracoordinated Co²⁺,which are not present in the basic glass,appeared in both the absorption and emission spectra.This indicates that Co²⁺ions entered the spinel phase ZnAl₂O₄/Mg Al₂O₄ and replaced Zn²⁺or Mg²⁺in the tetrahedral（T_d）sites.With the increase of crystallization treatment time,the absorption spectral and emission spectral intensities of the samples showed a trend of increasing and then decreasing,and the sample with 4h crystallization treatment showed the best absorption and emission properties.A comparison of the glass-ceramics prepared using raw materials with different valence states of Co oxides shows that the element Co exists as divalent Co²⁺ions in the spinel phase of the final glass-ceramics,whether it is doped with Co O or Co₂O₃.Moreover,the prepared glass-ceramics material was compared with other Co-doped matrix materials in terms of the ground state absorption cross sectionσ_gas at 1540 nm,and it was found that it can be used as a saturable absorber in Q-switch lasers.Transparent glass-ceramics of the Nd³⁺-doped ZMAS system were prepared,and the heat treatment regime of the basic glass was developed from the results of differential thermal analysis.Based on the X-ray diffraction results,it was determined that the main crystalline phase of glass-ceramics was ZnAl₂O₄/Mg Al₂O₄,and the secondary crystalline phase is Mg₂Ti O₄/Zn₂Ti O₄.The composition of the glass-ceramics did not change with the increase of the crystallization treatment time,and the crystallinity and the average grain size of spinel showed a trend of first increasing and then decreasing.The absorption spectra of the samples indicate that Nd³⁺enters the spinel lattice and occupies the A-site of the tetrahedral site（T_d）.The fluorescence spectra of the samples showed that the luminescence intensity of ⁴F_3/2→⁴I_J（J=9/2,11/2and 13/2）of the glass-ceramics samples was significantly higher compared with that of the base glass,and showed an increasing and then decreasing trend with increasing heat treatment time,and the samples with 1.5h crystallization treatment showed the best fluorescence performance,indicating that the luminescence intensity of Nd³⁺ions was closely related to the degree of crystallization.In addition,it exhibits a high-intensity⁴F_3/2→⁴F_11/2 emission transition near 1064 nm,indicating that this material is a potential laser material.It is found that the crystallinity of glass-ceramics affects the concentration of dopant ions in the microcrystalline phase,and then the optical properties can be regulated by controlling the degree of crystallization of glass-ceramics,which is a guideline for the preparation of glass-ceramics materials with excellent performance.