Dear Niaz Ahmad . It is measured by impedance spectroscopy (AC technique), which applies a sinusoidal potential at various frequencies to an electrochemical cell with blocking electrodes and records its response. See the link: https://dspace.mit.edu/bitstream/handle/1721.1/109539/Inorganic%20Solid-State%20Electrolytes%20for%20Lithium%20Batteries_Mechanisms%20and%20Properties%20Governing%20Ion%20Conduction_SI.pdf?sequence=3&isAllowed=y