Dielectric relaxation processes in Cd2Nb2O7 compound

This article reports a study on the dielectric relaxation processes of Cd2N b2O7 compound. Three dielectric relaxation modes I, II, and III were reexam ined. By using the Cole-Cole equation fitting of the frequency dependence o f dielectric constant and loss, we obtained more precise relaxation time da ta, compared to the data reported in the literature. The results indicate t hat the relaxation time for mode I follows the Arrhenius law with one slope rather than two slopes as reported in the literature in the frequency rang e of 10(2)-10(5) Hz. However, the parameters obtained from the Arrhenius la w fit are not physically reasonable. More physically reasonable parameters can be obtained by fitting the relaxation time to the empirical Vogel [Z. P hys. 22, 645 (1921)]-Fulcher [J. Am. Ceram. Soc. 8, 339 (1925)] relation wi th essentially the same fitting quality. A comparison of Cd2Nb2O7 with well known triglycine sulphate (TGS) is made. The similarity between the dielec tric response of Cd2Nb2O7 and TGS is emphasized. The physical mechanism of the relaxation modes is briefly discussed. With increasing dc bias, the thr ee relaxation modes were suppressed and eventually eliminated. This indicat es that the dielectric responses of Cd2Nb2O7 at zero dc bias are the sum ef fect of several dielectric modes with relaxation polarization superimposed on the ferroelectric-paraelectric phase transition. (C) 2000 American Insti tute of Physics.