Abstract
Electric conductivity relaxation times τ were obtained from impedance measurements of Pb(Mn 1/3 Nb 2/3 )O 3 ceramics. Two relaxation processes were discerned with use of derivative ∂ ε ′ /∂ (logf) and electric modulus M” approaches. The applied axial pressure X decreases the relaxation times above threshold pressure X thresh ≈ 50 MPa. In case of a hydrostatic pressure, the rate of ∂ τ /∂ p changes at p cr ≈ 0.9 GPa. The pressure effects and bi-vacancies role are described in framework of the Gate Model.