Cold sintering for Li1.5Al0.5Ge1.5(PO4)3 using LiNO3-LiOH as a transient solvent

• Published in: Japanese Journal of Applied Physics Vol. 60; no. 12
• Main Authors: Takashima, Kenji, Iwazaki, Yoshiki, Randall, Clive A.
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 01.12.2021; Japanese Journal of Applied Physics
• Subjects: Ceramic powders; Ceramics; Cold pressing; Cold sintering; Cold sintering process; Dissolution; Grain boundaries; Inorganic materials; Ion currents; lithium aluminium germanium phosphate; low-temperature sintering; Sintering (powder metallurgy); solid electrolyte; solid-state batteries; Solvents
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/ac33cf

The cold sintering process (CSP) is an innovative technique to densify ceramic powders at ultralow temperatures by applying uniaxial pressure and using a transient solvent. However, obtaining dense Li1.5Al0.5Ge1.5(PO4)3 (LAGP) ceramics, which have high ionic conductivity, by CSP has been a challenging subject, because incongruent dissolution from the powder to a solvent can happen during CSP, and that deteriorates the grain boundary. In this study, LiNO3-LiOH salt is used as the transient solvent to suppress the incongruent dissolution. LAGP ceramics densified by the CSP at 220 °C and 400 MPa for 5 h have no damage at the grain boundary. As the result, the total ionic conductivity reaches 1.9 נ10−5 S cm−1, which is the highest value ever reported among LAGP ceramics prepared by CSP only using inorganic materials.