Enhancing lithium-ion conductivity in NASICON glass-ceramics by adding yttria†
We demonstrate that the ionic conductivity of Li1+xAlxGe2−x(PO4)3 glass-ceramic electrolytes can be tailored by adding Y2O3 to Li2O–Al2O3–GeO2–P2O5 melts. We found that the addition of 5 vol% Y2O3 causes noticeable changes in further glass crystallization process as the key parameters (glass crystallization temperature, viscosity and others) are affected. Small-angle neutron scattering data suggest that Y-containing glasses are suddenly crystallized upon heat treatment producing uniform Li1+xAlxGe2−x(PO4)3 ceramics. Due to the lower resistance of intergrain interfaces, such samples demonstrate a specific ionic conductivity of 0.5 mS cm−1, which is nearly 5 times higher in comparison to Y-free ceramics, prepared under similar conditions. We speculate that such an effect is caused primarily by better intergrain contact in Y-containing ceramics, along with better ionic transport in the grain bulk as evidenced by 7Li NMR.