AC electrical behaviour of a Pb2CrO5 ceramic sample with surface electrodes

ac measurements (1 Hz–10 kHz) have been carried out on a Pb₂CrO₅ ceramic sample (with surface electrodes) at room temperature as a function of voltage and intensity of visible light illuminating the sample. Cole-Cole complex impedance plots show that the electrical behaviour of Pb₂CrO₅ is strongly modified when the sample is illuminated. The bulk conductance of the sample is found to increase with increasing light intensity indicating that this dielectric material becomes semiconducting due to the photogeneration of free charge carriers in the conduction band. The dielectric constant of the sample is enhanced by illumination probably due to light-dependent space charge effects in a manner where the dielectric's relaxation time (=RC=0.7 ms) remains constant with light intensity. On the other hand, both the bulk conductance and geometrical capacitance of the sample have been found to be almost independent of the applied voltage.