| Transparent glass-ceramics comprise nano-crystals embedded in a glass matrix. Due to the ultra-fine microstructure, the glass-ceramics have some excellent properties, such as high transparency, high temperature capability etc. In this paper, the MgO-Al2O3-Si02 glass-ceramics was investigated by DTA, XRD, SEM and UV-VIS-NIR scanning spectrophotometer. The colorless transparent MAS glass-ceramics using TiO2 and ZrO2 as nucleation agents, were prepared by two-step heat-treatments. The 0-4% content of ZnO adding to the MAS glass to reduce the viscosity in glass melting and keep the spinel as the main crystalline phase unchanged. Meanwhile, the crystallization behavior and microstructure of the transparent MAS glass-ceramics with different content of nucleating agents were investigated. It has deep research on the composition, heat-treatment, microstructure and the performance for transparency of glass-ceramics, and the concrete relationship between them would be studied. The results show as follows:The MAS glass-ceramic (without ZnO) crystallized at 950℃is transparent, and the transmittance in visible spectra region reaches 83%, in near infrared spectra region over 90%, but in UV region 0%. As the crystallization temperature increased, the mean particle size becomes bigger and the transmittance in visible light spectra decreases. Meanwhile, the crystalline phases in glass-ceramics become complicated, the spinel (MgAlO4), sapphirine (Mg3.5Al9Si1.5O20), ZrTi2O4 and SiO2 would precipitate successively.By experienced the heat-treatment 830℃/4h+950℃/1.5h, the MAS glass-ceramics (containing ZnO) with spinel(MgAl2O4) and gahnite(ZnAl2O4) as the main crystal phase are transparent, and the transmittance is over 85% in visible light wavelength. When adding 2% ZnO, the mean particle size of the glass-ceramic significantly decreases to 27nm. As the increasing of ZnO, the ultraviolet cut-off wavelength move to the shorter wave.The composition with 5%TiO2+3%ZrO2 (I# glass) as nucleating agents is the proper for preparing colorless transparent glass-ceramics. The I# glass crystallized at 900-950℃can obtain colorless transparent glass-ceramics only containing spinel (MgAlO4) crystal phase. The nucleating temperature changed from 740 to 800℃has little influence on the species and quantities of the crystal phase. Therefore, the heat-treated temperature range of preparing transparent glass-ceramic is relatively wide. After heat-treated at 770℃/4h+950/1.5h, the I# glass has mean crystal size 18.4nm, and the crystal distributes uniformly with standard deviation value 2.0.
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