INVESTIGATION OF REACTION BONDING OF A LITHIUM SOLID ELECTROLYTE AND ITS APPLICATION TO LITHIUM-ALUMINUM ALLOYS

Abstract

The goals ofthis study were to unravel the mechanism ofthe liquid phase joining reaction between the LiYO2 electrolyte and the Y2O3-MgO lid used in the fabrication ofan EMF cell and second, to investigate the Li-Al binary alloy system by the EMF method. The joining occurs between the electrolyte tube and the inert lid when they are rap idly heated to 1325°C. It wasfound that the tube and the lid werejoined by reaction bonding in which Li2CO3 served a key role as the bonding agent and a sintering additive. When sufficient liquid phase fraction is present, the melt at the base ofthe tube reacts with the Y2O3 lid and forms a solid LiYO2 joint. This triggers a rapid densification process that propagates upward to the top ofthe tube. XRD, DTA and SEM were used to analyze the properties of LiYO2and the microstructure ofthe tube and the joint. The cell fabricated in this way worked steadily for several months in contact with liquid lithium or lithium alloy. The thermodynamic properties ofLi-Al alloys, including the liquid phase, the a-solution region, and the a + p two-phase region were investigated in the temperature range of370 to 750°C. The liquidus curve could be directly obtained from the EMF versus temperature plot. The solid-liquid phase boundary was consistent with data from the literature. The AG, AS and AH ofthe molten alloys up to 30% Li were derived from the measurements. The cell elaborated in this study can be used not only for phase diagram analysis, but also as a sensor for Li in molten alloys or possibly in high temperature batteries.