The intent of this study was to determine the effects of lithium flux on the elastic moduli of the solid electrolyte lithium lanthanum zirconium oxide (LLZO), with a goal of using the elasticity measurements as a gauge of Li dendrite growth. Several LLZO billets were prepared and analyzed using resonant ultrasound spectroscopy (RUS). The specimens of LLZO had Young's modulus, E, ranging from 90.7 GPa to 129.0 GPa, and the range for shear modulus, G, was 33.62 GPa to 50.65 GPa. Published values for LLZO list E = 149.8 GPa and G = 59.6 GPa at 3% porosity [Ni 2012]. The cause for the difference in elastic moduli values is uncertain. Porosity alone was determined not to account for the difference in moduli among specimens. A microcrack damage model predicted that surface microcracks induced by sanding would result in changes that are too small to be measureable by RUS. In order to predict whether Li dendrite growth would be detectable by elasticity measurements, several models were considered for LLZO and Li forming a fiber/matrix composite. In addition to fibers (dendrites), Li solid solutions may also occur, so models based on Nordheim's rule were also considered.
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