Enhanced densification and conductivity of LAMGPB glass-ceramic electrolyte through ultra-fast high-temperature sintering

The promising use of NASICON-type ceramics electrolytes highlights the need for rapid, energy-efficient and scalable ceramic processing. Ultra-fast high-temperature sintering (UHS) overcomes the limitations of conventional sintering including prolonged times, high energy demand and lithium volatilization, which can adversely affect ionic conductivity and structural stability. Here, UHS is investigated for the sintering of a modified Li1.5Al0.3Mg0.1Ge1.6(PO4)3 + 0.5 wt% B2O3 composition (namely, LAMGPB) obtained through melt-casting, in comparison with a commercial LAGP counterpart. The densification, crystallization behavior and microstructural evolution of the two amorphous systems are investigated across increasing currents. Results demonstrate that the high heating rates achieved through UHS promote rapid densification and enable the formation of a fully crystalline and pure LAGP ion-conducting phase in both systems. Electrochemical impedance spectroscopy reveals an enhanced total ionic conductivity for LAMGPB compared to commercial LAGP. A reduced grain boundary resistance is indeed observed for this system, attributed to the improved grain size and cohesion induced by the segregation of amorphous B2O3 at the grain boundary. Overall, this study sheds light on the correlations between the crystal phase evolutions, microstructural features and electrochemical performances of NASICON-type systems, unravelling the effect of UHS sintering and oxide doping on these aspects.