Synthesis and characterization of lithium-ion-conductive glass-ceramics of lithium chloroboracite Li_4+xB₇O_12+x/2Cl (x = 0–1)

Abstract

Nearly single-phase and almost fully-crystallized glass-ceramics of lithium chloroboracite Li_4+xB₇O_12+x/2Cl (x = 0–1) were prepared by crystallization of precursor glasses derived from the Li₂O–B₂O₃–LiCl ternary system. The crystal structure of Li₄B₇O₁₂Cl (x = 0) was refined by the Rietveld method in the space group F43c (no. 219). The precursor glass partially crystallized into Li₂B₄O₇ at ∼500°C and was subsequently converted to Li₄B₇O₁₂Cl at ∼600°C. The decomposition of Li₄B₇O₁₂Cl started at ∼700°C. The conductivity of Li₄B₇O₁₂Cl was much higher than that of Li₅B₇O_12.5Cl (x = 1). The glass-ceramic sample with the highest weight fraction of Li₄B₇O₁₂Cl (∼0.98 of crystalline part with a degree of crystallinity of ∼0.96) exhibited a conductivity of ∼4.6 × 10⁻⁴ S cm⁻¹ at 200°C and an activation energy of conductivity of ∼0.52 eV.