Why do ionic conductors usually become less electrically conductive under high pressure?

Ionic conductors generally experience a decrease in electrical conductivity under high pressure because the applied force causes the collapse of the pathways required for ion migration.1

In crystalline solids, ionic conduction occurs through a process of ion hopping, where ions move from their lattice sites into adjacent vacancies or interstitial spaces. For this movement to occur, the crystal structure must provide sufficient space for the ions to migrate. Under high pressure, materials typically undergo structural transformations to denser, more closely packed atomic arrangements. This increased packing efficiency reduces the available volume and effectively closes the pathways that ions use to hop through the lattice, thereby inhibiting their mobility and reducing the material's overall conductivity.231