Fig. 5 presents the room temperatur

Fig. 5 presents the room temperature dielectric constant (ε’) and dielectric loss (tanδ) properties of ZnO-BT composites over a frequency range from 10 Hz to 1 MHz. The dielectric constant and dielectric loss decreased quickly with the increase of BT content at low frequencies. This behavior became evident for 80ZnO-20BT and 50ZnO-50BT. The presence of high capacitance associated with high dielectric loss at low frequencies is related to Maxwell-Wagner polarization 28. In particular, dielectrics loss peaks are resolved for 80ZnO-20BT and 50ZnO-50BT. These loss peaks should not be associated with any phase transition and reinforce the statement of the Maxwell-Wagner polarization 29. We presented the dielectric loss also on a logarithmic scale for better visualization (insert in Fig. 5b). It is interesting to observe that the low densities composites of 10ZnO-90BT presented the lowest dielectric loss and permittivity. Besides, the pure ZnO showed, together with the 90ZnO-10BT, the highest values of permittivity and dielectric loss.