Wen-Chang Su

Effects of the MnO additives on the properties of Pb(Fe2/3W1/3)-PbTiO3 relaxors : Comparison of empirical law and experimental results

In this paper, pure and 0.15wt%MnO additives of (1−x)Pb(Fe2∕3W1∕3)O3–xPbTiO3 [(1−x)PFW−xPT] with x=0.1, 0.2, 0.3, and 0.4 were synthesized by the conventional solid state reaction method. The dielectric diffusion properties were investigated with the empirical law. The lattice structure was found to transfer from tetragonal to pseudocubic and the diffusion phase characteristic is more notable as decreasing PbTiO3 compositions or adding MnO additives. Moreover, the dielectric loss is improved and the space charge polarization effect is vanished as adding MnO additives in 0.7PFW-0.3PT compounds. We suggested it was probably due to the lead vacancy which is substituted by the manganese ions or the interstitial manganese ions intervene into the interstice between the positive and negative ions.

Dielectric behaviors of Pb(Fe2∕3W1∕3)-PbTiO3 relaxors: Models comparison and numerical calculations

Regarding the dielectric characteristics of the diffusion phase transition (DPT) in ferroelectric relaxor materials, several researchers have provided similar but different laws to explain these phenomenon. These laws, presented by Burfoot et al. and Eiras et al., have been proven to provide a better explanation, especially the dielectric diffusion phenomenon, of the incomplete DPT materials if compared with the models presented by Smolensky, and Isupov. However, the differences in fitting adaptability and the physical and mathematical meanings between these two laws have never been discussed. In this paper, we analyze these two laws in the (1−x)Pb(Fe2∕3W1∕3)-xPbTiO3 [(1−x)PFW-xPT] relaxor system using the statistical regression theory. We find that the laws of both Burfoot and Eiras demonstrate the same adaptability and provide smaller estimation bias on the samples than the models of Smolensky and Isupov, despite the complete or incomplete DPT characteristics. When x is smaller, the samples tend to be c...

Effects of synthesized method on glassy behavior and freezing process of 0.75PFW–0.25PT ceramics

Two different methods, the conventional direct oxide synthesized method and the two-step indirect synthesized (IS) method, were employed to synthesize the 0.75Pb(Fe2/3W1/3)O3–0.25PbTiO3 ceramics. The low-field dielectric responses were investigated using the empirical law and the Curie–Weiss law. The temperature-dependent local ordering parameters were derived from the experimental results using the spin-glass model and the modified-Landau theory separately. According to the experimental data and the fitting results, it is concluded that the temperature-dependent local order parameters are changed from a short-range-ordered relaxor to a long-range-ordered ferroelectric state using the IS method. On the basis of the physical concepts of the spin-glass model, the modified-Landau theory and the ordering models, it is suggested that local polarizations are affected not only by degree of ordering but also by space charge polarization. In contrast, the glassy behavior of local polarization is affected only by d...

Dielectric Behavior of PFW-PT Relaxors: Model-Parameters Extraction

In this paper, we systematically present the physical and mathematical meanings of the parameters used in Burfoot et al.s and Eiras et al.s model. Based on our experimental results in (l-x)PFW-xPT relaxor system and the theoretically modelling results, it is shown that the parameter values in Burfoot et al.s model and Eiras et al.s model have not any variations after normalizing the maximum dielectric constant and shifting the temperature of the maximum dielectric constant Tm. It is also shown that the parameters in Eiras et al.s model have better physical and mathematical meanings.