Mechanical properties of NaSICON: a brief review

A variety of rechargeable Na batteries are under development for use in energy storage systems. For these batteries, a Na-ion conducting solid electrolyte is desired. One such electrolyte under consideration is NaSICON (Na Super Ionic Conductor). One important aspect of the NaSICON electrolytes that has been overlooked is their mechanical properties. Such information is required if NaSICON has to be used as a solid electrolyte in rechargeable Na batteries that exhibit long life cycle and high power. This paper reviews the elastic, plastic, and fracture properties of NaSICON electrolytes. Young’s modulus values for NaSICON range from ~ 56 to 97 GPa with Poisson’s ratio ~ 0.26. Hardness values determined by micro-indentation for NaSiCON are 4.4–4.9 GPa. The value of the Gilman-Chin parameter suggests the bonding in NaSICON is covalent. As a result of its covalent bonding, NaSICON exhibits a high Peierls which leads to low fracture toughness, with KIC values ~ 1–1.5 MPa m0.5. The fracture strength of NaSICON is between 50 and 110 MPa and is controlled by the amount and size of the second-phase ZrO2 particles.