Lithium ion conductivity, crystallization tendency, and microstructural evolution of LiZrxTi2-x(PO4)3 NASICON glass-ceramics (x = 0 - 0.4)

Abstract

In this research, NASICON type (LiZr_XTi_2-X(PO₄)₃) glass-ceramics were fabricated (x = 0.1, 0.2, 0.3, 0.4). Lithium-ion conductivity along with the crystallization tendency and microstructural features were examined in this regard. Parent glasses obtained through melt quenching were converted to the glass-ceramic specimens after one-step heat treatment procedure. The resultant glass-ceramics were deeply explored by means of different techniques including scanning electron microscope, differential thermal analysis, X-ray diffractometry, and ionic conductivity measurements. According to the obtained results, presence of Zr⁴⁺ ions in the glass network and its gradual increase caused the enhanced crystallization temperature as well as declined crystallinity and microstructure coarsening. In all studied glass-ceramics, LiT₂(PO₄)₃ solid solution was the dominant crystalline phase and Zr⁴⁺ ions partly substituted in the structure of this crystalline phase. Moreover, presence of Zr⁴⁺ ions in the glass composition resulted in diminished lithium-ion conductivity of corresponded glass-ceramics at ambient temperature. Consequently, total conductivity of specimen with the highest level of ZrO₂ (x = 0.4) was measured to be 0.78 x 10^-5 Scm^-1, being considerably less than ionic conductivity of the base (x = 0) glass-ceramic (3.04 x 10^-5 Scm^-1). It seems that less crystallinity of ZrO₂ containing glass-ceramics decreases required connectivity between the lithium-ion free paths and is responsible for the diminished ionic conductivity of these specimens.