Giant dielectric permittivity caused by carrier hopping in a layered cuprate Bi2Ba2Nd1.6Ce0.4Cu2O10+δ

The ceramic sample of a layered cuprate Bi2Ba2Nd1.6Ce0.4Cu2O10+δ, so-called Ba-based Bi-2222 compound was studied by the measurement of the temperature (80-300 K) and the frequency (20-106 Hz) dependence of the complex dielectric permittivity. The dielectric constant was measured as high as ∼1000 at 1 kHz and 300 K with relatively low dissipation factor. However, it decreases systematically with decreasing temperature or with increasing frequency due to the dipolar relaxation process. This thermally activated relaxation process plays a dominant role for the low frequency dielectric response. Furthermore, the frequency-dependent ac conductivity was found to obey the power law σ=Aωs. The results were interpreted in terms of Pike's model of hopping transport of localized charge carriers which yields explicitly the ωs behavior and the temperature dependence of s. And we calculated the ionization energy of localized carriers Wm=0.35 eV for the present sample