Abstract: Li₂O-Al₂O₃-SiO₂ system ultra-low expansion glass-ceramics is a kind of low expansion optical material with excellent performance, it has low thermal expansion coefficient and good transparency. Domestic high quality ultra-low expansion glass-ceramics has been subject to technical constraints and it is difficult to achieve mass production. In this study, high quality ultra-low expansion transparent glass-ceramics with near-zero thermal expansion coefficient were successfully manufactured by melting method, stirring process and suitable heat treatment system, the appearance of the product were complete, there were basically no bubbles, stripes and other defects inside the product. The thermal expansion coefficient, stress birefringence and flexural strength of the superior product were tested. The results show that the coefficient of thermal expansion of the superior product is 1.6×10^-8 K^-1, the stress birefringence is less than 2 nm/cm, the flexural strength is 171 MPa, and the quality has reachedZERODUR zero grade. The phase composition, surface morphology and microstructure of the product were analyzed through XRD, SEM and TEM. The main crystalline phase of the product is β-quartz solid solution, the content of the crystalline phase is high and the distribution is uniform, the grain size is tens of nanometers, which ensures the extremely low coefficient of thermal expansion and high transparency.

Key words: Li₂O-Al₂O₃-SiO₂, ultra-low expansion transparent glass-ceramics, β-quartz solid solution, heat treatment