Antiperovskite 1 Electrochemical impedance spectroscopy 1 Electrochemical-impedance spectroscopies 1 Grain boundaries 1 Grain boundary resistance 1 Grain interface Grain-grain boundaries 1 Interfacial resistances 1 Ions 1 Li ion conductivities 1 Lithium compounds 1 Solid electrolytes 1 Structural defect 1 Thermal expansion 1 Thermal expansion coefficients 1 X ray photoelectron spectroscopy 1 X-ray techniques 1