This study elucidates the roles of strain gradients in enhancing both electronic and ionic conductivity of Nb doped lead zirconate titanate (PNZT) films. Increasing the applied strain in bent PNZT films from 0 to 0.5% reduced the energy barrier for vacancy diffusion from 0.75 ± 0.1 to 0.5 ± 0.1 eV, resulting in an increase in mobile \(\:\left[{\text{V}}_{\text{O}}^{\cdot \cdot}\right]\) from 2.1 ± 0.2 × 1018/cm3 to 1.6 ± 0.4 × 1019/cm3. Notably, \(\:{V}_{O}^{\cdot \cdot}\) migration was detected even in bent samples not subjected to prior electrical degradation. The enhancement of migration is attributed to the electric field induced by coupled flexoelectric and piezoelectric effects. The increasing population of mobile \(\:{\text{V}}_{\text{O}}^{\cdot \cdot}\) due to bending strain enhances electron trapping by Ti4+ ions, raising the electronic conductivity. Concurrently, hole hopping between Pb2+ and Pb3+ decreases with increasing bending strain, indicating a decline in hole concentration and a shift in the n-p transition to higher \(\:{p(O}_{2})\) and temperature ranges. In pristine films on Ni metal foils, increasing the bending strain from 0 to 0.5% increased the volume fraction of a-domains from 15 to 64% due to ferroelastic domain reorientation. Consequently, the reversible Rayleigh coefficient \(\:{\epsilon\:}_{init}\) rose from 540 ± 6 to 790 ± 8, as the permittivity of a-domains is higher than that of c-domains. Furthermore, ferroelastic domain reorientation increased the concentration of non-180° domain walls, amplifying the irreversible Rayleigh parameter, α from 28 ± 4 to 47 ± 5 cm/kV. In the electrically degraded state, both \(\:{\epsilon\:}_{init}\:\) and α decreased, due to (1) loss of switchable units from localized dielectric breakdowns, (2) changes in domain configurations, and (3) the internal bias field. These results will influence the vast majority of piezoelectric microelectromechanical systems which utilize bending to enhance displacements.
