It can be seen from Fig. 7(a)–(d), that the ɛ values of all the samples are higher at low frequencies (1 kHz) and are found to decrease with increasing frequency exhibiting dielectric dispersion. It is interesting to note from the figure that the sharp antiferromagnetic peak broadens and also shifts to high temperature side with increasing frequency, which is a typical characteristic behavior of a relaxor material. The relaxor behavior of the sample can be explained on the basis of soft phonons modes [28]. In normal ferroelectrics, displacement of ions over a long range generates Lorentz field. In the case of ABO3-type perovskites, Lorentz field is in a direction which promotes displacement of ions. Therefore, soft phonon mode freezes at a certain temperature, which creates normal phase transition [29]. On the other hand, in relaxor ferroelectrics, the soft mode phonons cannot spread in one particular direction and the behavior is responsible for the observed broadness of the peak with increasing frequency.