Also, the results revealed that the value of ε′ obtained for Al doped sample was much higher than that of pure ZnO ceramics, and it increases with the increase of Al content. As shown in Fig. 5(b), at frequency below 103 Hz, the dielectric loss is very high and it decreases sharply with the increase of frequency, it remains at low values (∼0.4) in 103∼105 Hz, and then increases greatly with the further increase of frequency. On the other hand, it is also noticeable that dielectric loss increases slightly when Al is incorporated into ZnO lattice.