Thermal-assisted cold sintering study of a lithium electrolyte: Li_13.9Sr_0.1Zn(GeO₄)₄

The Thermal-Assisted Cold Sintering Process (TA-CSP) was applied to Li_13.9Sr_0.1Zn(GeO₄)₄ (LSZG), a lithium ion conducting electrolyte. The powders were both decomposed and densified between 120 °C and 200 °C under a cold sintering process with an uniaxial pressure of 300 MPa for 1 h and a water transient liquid phase. Then these glassy phases can be recrystallized with a second thermal annealing process with temperatures at 800 °C under a 5-h hold in air. The annealed CSP sample has smaller grain size than those processed with much higher temperature conventional sintering. The electrical properties of the cold sintered LSZG were characterized after the recrystallization process with electrochemical impedance spectroscopy over a temperature range between 25 °C and 400 °C. The data suggests that the lithium ion conductivity is 3.0 × 10⁻² Scm⁻¹ at 400 °C; this property is competitive with the conventional sintered samples processed at 1150 °C, and also the best performance reported in the literature. So, the CSP process followed by a recrystallization shows much low temperature advantage over the conventional sintering of the LSZG system.