Effect of sintering temperature and sintering additives on ionic conductivity of LiSi₂N₃

Abstract

The effect of sintering temperature and sintering additives on the ionic conductivity of LiSi₂N₃ was studied by performing complex impedance measurements. LiSi₂N₃ materials were fabricated by the reaction of Li₃N, Si₃N₄, and sintering additives at temperatures of 1873–2073 K. Dense hot-pressed bodies were obtained at 1973–2073 K in the case of undoped LiSi₂N₃ and at 1873 K in the case of Y₂O₃, CaF₂, and B₂O₃ addition. The ionic conductivity increased greatly with increasing sintering temperature and exhibited a strong dependence on the type of sintering additive. When the sintering temperature was constant at 1873 K, although the conductivities of Y₂O₃-doped LiSi₂N₃ and CaF₂-doped LiSi₂N₃ were lower than that of undoped LiSi₂N₃, the conductivity of B₂O₃-doped LiSi₂N₃ was higher than that of undoped LiSi₂N₃. The enhanced conductivity of B₂O₃-doped LiSi₂N₃ can be attributed to the increase in the density of the sintered material without the formation of a phase of significant resistance at the grain boundaries.