Dense and high flexural strength cordierite ceramics doped with Li2O

High-strength cordierite ceramics with Li2O were fabricated by non-pressure sintering. The results showed that the addition of Li2O significantly reduced the sintering temperature and expanded the sintering range. Additionally, the mechanical strength of the samples clearly increased after Li2O doping. In particular, the sample with 0.5 wt% Li2O sintered at 1250 degrees C showed the best properties, with a flexural strength of 178.6 MPa and a thermal expansion coefficient of 2.1 x 10-6 degrees C- 1. Its flexural strength is much higher than samples without Li2O and the cordierite ceramics prepared by non-pressure sintering reported in the literature. The high density of the sample (2.52 g cm-3) is the main reason for its excellent mechanical properties. Furthermore, first-principles calculations verify that Li+ dopants insert at the vacant channel of alpha-cordierite crystal with six-fold coordination, which may reduce the anisotropy of the thermal expansion coefficient of alpha-cordierite, thus improving the strength of ceramics.