Effect of composition on sinter-crystallization and properties of low temperature co-fired α-cordierite glass–ceramics

This article investigates effect of composition, including SiO2 and impurity defined to contain K2O, Na2O, Fe2O3, etc., from K-feldspar, on sinter-crystallization and properties of the low temperature co-fired α-cordierite glass–ceramics. Increasing impurity content from 5.72 wt% to 9.16 wt% leads to enhanced crystallinity, formation of leucite and more pores but the crystallinity and porosity decreased with a further increase to 10.8 wt%. The main impurity K2O is critical for formation of α-cordierite and leucite. Only α-cordierite was precipitated from the glasses with different SiO2 contents but an increase of SiO2 content slightly improves their densification. The impurity and SiO2 contents greatly affect the properties of glass–ceramics. Notably, some glass–ceramics from K-feldspar show high densification at low temperature, low dielectric constant (6–8), low loss (about 0.005), appropriate linear CTEs (4.32–5.87 × 10−6 K−1) and flexural strength (above 100 MPa), all of which meet the requirements of LTCC substrates.