Effect of Li2CO3–Bi2O3 doping on the low-temperature sintering, structure, and dielectric and mechanical properties of MgO–TiO2(w) ceramics

Dense MgO–12% TiO2(w) ceramics containing 12 wt% TiO2, which were doped with Li2CO3–Bi2O3 composite sintering aids, were prepared at a low sintering temperature of 950 °C in this study. The effects of sintering additives on the sintering characteristics, phase composition, microstructure, and dielectric and mechanical properties of the ceramic samples were systematically investigated, and the influences of their phase composition and microstructure on the dielectric and mechanical properties were examined. The introduction of sintering aids produced a new Bi4Ti3O12 phase in the sample structure, while the residual Bi2O3 mixed with the newly formed Mg2TiO4 and Bi4Ti3O12 phases distributed at MgO grain boundaries formed a structure surrounding MgO grains. This structure filled the pores in the ceramic sample, which increased its density and enhanced the mechanical properties. At a Li2CO3–Bi2O3 content of 15 wt%, the density, flexural strength, and Vickers hardness of the ceramic samples reached their maximum values of 3.4 g/cm3, 218.9 MPa, and 778.7 HV, respectively. However, the further increase in the Li2CO3–Bi2O3 content deteriorated their dielectric properties although the dielectric constant and dielectric loss remained below 13.4 and 2.1 × 10−3, respectively. The findings of this work indicate that Li2CO3–Bi2O3 sintering aids can significantly lower the sintering temperature of MgO–12% TiO2(w) ceramics and control their dielectric and mechanical properties through microstructural changes.