Effect of dc bias on dielectric properties of Cd2Nb2O7 ceramics

The effect of dc bias on dielectric properties of cadmium pyroniobate Cd2Nb2O7 ceramics is studied in this article. Without dc bias, two obvious dielectric peaks around 80 and 180 K are observed; by applying dc bias, the two peaks are greatly suppressed and finally eliminated at 15 kV/cm, however, a peak with no frequency dispersion shows up at 192 K. The results show high electric-field tunability of the dielectric constant with a low dielectric loss at radio frequencies. The electric-field dependence of the dielectric constant around 80 K can be well described by the modified Devonshire relation including the Langevin-type cluster term, i.e., epsilon (E)=epsilon (1)-epsilon E-2(2)+epsilon E-3(4)+(P(j)x(j)/epsilon (0))[cosh(Ex(j))](-2). The fit parameters indicate that the polar cluster carries polarization P=similar to0.28-0.65 mC/m(2) with the cluster size of L=similar to 24-30 nm. (C) 2001 American Institute of Physics.