The effect of hydrostatic pressure on the ionic conductivities in β -PbF2 /3-Pbi__xM™F₂+(_m_₂)_x (where M^m = Na⁺, Cd⁺², Tb⁺³, U⁺⁴), LaF3 and La₁__xCa_xF_3-x has been investigated in the temperature range between 300 K and 700 K for pressures up to 0.25 GPa (for β -PbF₂) and 0.8 GPa (for LaF₃). The activation volumes of defect formation and migration, impurity defect segregation and dissociation were determined from the effect of pressure on the conductivity. Keyes' treatment based on the strain energy Zener model in Griienisen approximation was used to estimate theoretical values of activation volumes.