Relaxation peaks can be explained on the basis of the effect of other parameters (i.e. temperature/frequency) on the dielectric properties of the insulating material. If the dielectric response of the insulating material is measured with changes in the frequency, so at different frequency region the response will be differ. So according to the frequency region we can explain the relaxation peaks. I tried to explain in the attached paper, which may be helpful for you.
The dielectric peaks are affected by factors as: ionic species, impurezas, temperature and frequency. At low frequency is possible to observe a Maxwell-Wagner polarization.