Effects of Al2O3 addition on the sintering behavior and microwave dielectric properties of CaSiO3 ceramics

The effects of Al2O3 addition on the densification, structure and microwave dielectric properties of CaSiO3 ceramics have been investigated. The Al2O3 addition results in the presence of two distinct phases, e.g. Ca2Al2SiO7 and CaAl2Si2O8, which can restrict the growth of CaSiO3 grains by surrounding their boundaries and also improve the bulk density of CaSiO3–Al2O3 ceramics. However, excessive addition (≥2 wt%) of Al2O3 undermines the microwave dielectric properties of the title ceramics since the derived phases of Ca2Al2SiO7 and CaAl2Si2O8 have poor quality factor. The optimum amount of Al2O3 addition is found to be 1 wt%, and the derived CaSiO3–Al2O3 ceramic sintered at 1250 °C presents improved microwave dielectric properties of ɛr = 6.66 and Q × f = 24,626 GHz, which is much better than those of pure CaSiO3 ceramic sintered at 1340 °C (Q × f = 13,109 GHz).