The effect of dc bias on dielectric properties of cadmium pyroniobate Cd2Nb
2O7 ceramics is studied in this article. Without dc bias, two obvious diele
ctric 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 rela
tion 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). Th
e fit parameters indicate that the polar cluster carries polarization P=sim
ilar to0.28-0.65 mC/m(2) with the cluster size of L=similar to 24-30 nm. (C
) 2001 American Institute of Physics.