Certain characteristic features of phase transition observed in many ferroelectric and antiferroelectric compounds and solid solution have attracted special attention. These features include especially the frequently observed broadening of the phase transition and several concomitant phenomena.
In this paper, dielectric properties of $(1-x)Pb(Fe_{1/2}Nb_{1/2})O_3ㆍxPb(Mg_{1/2}W_{1/2})O_3$ system are dealt with. Specimen were prepared by the conventional mixed oxide technique.
The work described in this paper falls naturally into three parts. The first part describes the identification of composition of x=0.55. The specimen of this composition shows the first order phase transition from the paraelectric phase to the ferroelectric one at -70℃ under atmospheric pressure with decreasing temperature. The next part deals with the effect of thermal shock on diffused phase transition (DPT) behavior of the specimen of x=0.885, 0.890, 0.895. The critical composition between DPT and sharp transition is proved to be at 0.885 < x < 0.890. Specimen of x=0.890 is found to change the transition behavior from sharp to DPT by the thermal shock, while x=0.885, x=0.895 do not change their original dielectric properties by the thermal shock. At the third part the critical stability factor, $ξ_{3c}$ defined by Fritzberg's polarization fluctuation model between the sharp and DPT is determined to be about 2.01x$10^7$ (V/m). The sharp transition occurs for the stability factor $ξ_3>ξ_{3c}$, where the DPT occurs for $ξ_3≥ξ_{3c}$.
