Antiferroelectric $PbYb_\frac{1}{2}Nb_\frac{1}{2}O_{3}$[PYN] which has the first order phase transition has a complete solid solution with ferroelectric $PbTiO_3$[PT]. It was reported that there is a diffuse phase transition [DPT] region (0.10 ＜ x ＜ 0.25 ) in the (1-x)PYN-xPT solid solution. Dielectric constant and P-E hysteresis loop were measured in the DPT region. Also, we can measure accurately a low frequency dielectric constant by using Lock-In Amplifier(EG＆G DSP 7260) from 0.1Hz to 100kHz. It can be confirmed that orthorhombic antiferroelectric phase is changed into pseudocubic DPT at x = 0.09 by the XRD analysis and the already mentioned dielectric analysis.
The increase of broadness and frequency dependency of $ε_{max}$ and also the change from double loop to slim loop give evidence for increasing relaxor behavior tendency with PT content. From the experiment by Lock-In Amplifier, we obtained that an anomaly of the dielectric loss in the logarithmic frequency domain is increasing with PT concentration. It can be inferred that there is an important relationship between relaxor and anomaly tendency which is thought to originate from the increase of polar cluster's concentration. We also try to obtain the relaxation time distribution g(τ) from the complex dielectric constant by using Tikchonov regularization method.
Double loop obtained by P-E hysteresis measurement is interpreted by the viewpoint of B-site ordering and related to the relaxor behavior.
