Pressure- and Temperature-Dependent Ionic Transport in Ag₄Zr₃S₈ Nanocrystal Pellets

Nanocrystal (NC)–derived solid electrolytes provide access to compositionally complex and metastable ion conductors, yet their measured transport properties are often dominated by extrinsic contact effects. We probe the coupled roles of temperature, uniaxial pressure, pellet microstructure, and electrode material on the electrochemical impedance response of Ag₄Zr₃S₈ NC pellets. Ag₄Zr₃S₈ NCs were synthesized via colloidal routes using distinct sulfur sources and consolidated into pellets with controlled surface chemistry. EIS was performed over 298–393 K and 0.43–8.67 MPa using blocking and non-blocking electrodes. Pressure-dependent Nyquist analysis shows impedance is overwhelmingly dominated by interfacial and constriction resistances, with pressure primarily reducing contact limitations rather than altering intrinsic ion transport. Temperature–pressure heat maps of the high-frequency resistance reveal thermally activated transport strongly modulated by mechanical contact and electrode compatibility. These results establish pressure-resolved impedance spectroscopy as a diagnostic framework for separating intrinsic and extrinsic transport contributions in NC-based solid electrolytes.