Effect of Ca-doping on the ionic conductivity of LiSi2N3 was studied. The compositions of Li1-2xCaxSi2N3 (x=0-0.2) were synthesized by the reaction of Li3N, Si3N4, and Ca3N2 at 1873 to 2073K. Ca was incorporated into the LiSi2N3 host lattice and formed the solid solution, Li1-2xCaxSi2N3. Activation energy for ionic conduction was decreased and ionic conductivity at room temperature was enhanced by Ca doping. At 298K, the ionic conductivity of densified Li1-2xCaxSi2N3 (x = 0.075) ceramics achieved 1.6 x 10−5Sm−1, almost 4 orders of magnitude higher than that of densified Li1-2xCaxSi2N3 (x = 0) ceramics (3.1 x 10−9Sm−1). The LiSi2N3 framework change by Ca doping decreased the interaction between the ions and increased the defects of the structure. Thus, mobile Li+ ion could migrate easier. Moreover, incorporation of aliovalent substitutional Ca2+ ions in the LiSi2N3 lattice might be expected to create a Li+ vacancy (VLi) for charge compensation (Li1-2xCaxVLiSi2N3), thereby increasing the number of mobile Li+ ions.

Effect of Ca-Doping on the Ionic Conductivity of LiSi2N3. E.Narimatsu, Y.Yamamoto, T.Takeda, T.Nishimura, N.Hirosaki: IOP Conference Series - Materials Science and Engineering, 2011, 18[9A], 122001