Influence of bismuth additives on the dielectric properties of Pb(Fe sub(2/3)W sub(1/3)) sub(0.7)Ti sub(0.3)O sub(3) ceramics

In this study, the effects of bismuth additives are investigated based on the dielectric properties by the empirical law and the order-disorder model for the Pb(Fe sub(2/3)W sub(1/3)) sub(0.7)Ti sub(0.3)O sub(3)-x wt.% Bi sub(2)O sub(3) ceramics. The grain size initially increased and the diffused phase transition property initially decreased at x = 0.25 wt% and then these properties reversed. In addition, the space charge polarization is weakened and then reinforced when the amount of bismuth additives increases. According to these experimental results and the model fitting results, it is concluded that bismuth additives can induce the random-site 1:1 order and change the dielectric properties from relaxor ferroelectric to normal ferroelectric by substituting bismuth ions for the lead vacancies. Furthermore, excess amounts of bismuth additives impede the grain growth and change the dielectric properties from normal ferroelectric to relaxor ferroelectric.