Research On The Powder Preparation, Sintering Behavior And Dielectric Properties Of Lithium Metasilicate

In recent years, Li2SiO3has attracted significant attention due to its good tritium solubility, physical and chemical stability at high temperature and its good mechanical stability. This paper focused on the preparation of Li2SiO3powder, the low temperature sintering behavior and dielectric properties of Li2SiO3ceramic and Ca-Li-Si composite have also been investigated.First, Li2SiO3powder was obtained via solid state reaction process. By using Li2CO3and SiO2as raw materials, pure Li2SiO3powder has been successfully synthesized after calcined at800℃for4h. Both the Li2SiO3ceramics and Ca-Li-Si composite could be sintered at about800℃by doping with appropriate sintering additives and presented good dielectric properties. Typically, when1%B2O3+2%MgO added, the Li2Si03could reach a high density (2.46g/cm3) and presented good dielectric properties (ε=6.47, tanδ=5.07×10-4at2MHz). For Ca-Li-Si composite, when the CaSiO3/Li2SiO3ratio was2/1, the sample doped with1%B2O3+1%MgO presented high density (2.64g/cm3) and good dielectric properties (ε=7.1, tanδ=7.86×10-4at2MHz).Then, hydrothermal process was applied to synthesize the Li2SiO3powder. The results show that pure lithium metasilicate(Li2Si03) powder with the grain size of about100-200nm and stable structure could be synthesized at100℃. Higher temperature, longer hydrothermal time and pH value (13.7) were beneficial for the forming of Li2SiO3powder.Finally, Li2SiO3powder was prepared via mechanical milling process by using LiOH·H2O and TEOS as raw materials. By adjusting the concentration of LiOH·H2O to as high as5.00M, pure Li2SiO3powder with small grain size of about100nm and high thermal stability has been successfully synthesized at-20℃after milling for120h. This nano Li2SiO3powder could be sintered at800-900℃by adding some B2O3or ZnO. The ε of this Li2SiO3ceramics were lower that those obtained via solid state reaction. Ca-Li-Si composite which using this nano Li2Si03powder as raw material was also sintered at800-900℃by adding some ZnO as additive. This Ca-Li-Si composite presented very low dielectric constant (the lowest ε was only1.47), and might become a promising super-low dielectric constant material.