Research On Glass-Ceramics With Negative Coefficient Of Thermal Expansion Used As Fiber Bragg Grating Substrate

This paper details the properties and characteristics of the β-eucryptite glass-ceramics with negative CTE (Coefficient of Thermal Expansion) that have been developed to bond to substrates for compensating the thermal variations in fiber Bragg gratings. And by mean of DTA, XRD, SEM techniques, the research work emphasized on the crystal phases structure, thermal expansion, and mechanics capability of the β-eucryptite glass-ceramics.Firstly, the preparation technology of the material was investigated, including the design composites, melting, and crystallization of the sampled glasses. Secondly, the phase transition and microstructure of glass-ceramics were investigated. The original glass had phase separation under 690℃. The metastable P-quartz s.s. (solid solution) first precipitated at 870 ℃. Crystallization from 1000℃ to 1050℃ comes into being the P-spodumene (Li2O-Al2O3-4SiO2) s.s. phase. When the temperature is up to 1050℃, the P-eucryptite s.s. is appeared and gradually increases. While the temperature is up to 1300℃, the crystalline grain grow greatly (5~10μm). This β-eucryptite phase begins to dissolve at 1320℃ or above where the tielite (Al2TiO5) is apparently unstable and decomposed to corundum (Al2O3) and rutile (TiO2). Thirdly, in this dissertation, the influence of composition, crystallization temperature, and time on CTE were investigated detailedly. Furthermore, the effect of nucleation reagent on crystallization capability were researched, and the mechanical performance, density, chemical stability of the samples were measured respectively. Finally, a reasonable composition and synthesis technology of β-eucryptite glass-ceramics have been put forward.