The effect of persistent photoconductivity is observed in zinc oxide (ZnO) ceramics together with persistence of the electron paramagnetic resonance (EPR) spectra of defects and impurity centers in the samples. The spectral and time dependences of the EPR signals and microwave photoconductivity are investigated under excitation by light with different quantum energies below the ZnO band gap. The mechanisms of the persistent photoconductivity and coexistence of pnotoconductivity and optically induced EPR spectra after switching off the light are discussed. Based on the experimental results it is concluded that surface and intergranular conductivities dominate in ZnO ceramics.
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