Temperature- and Frequency-Dependent Dielectric Properties of La1.5Sr0.5NiO4−δ

We report the temperature-dependent resistivity and dielectric function (1 kHz ∼ 3 MHz) of a charge ordering system La1.5Sr0.5NiO4−δ. The primary data of ac impedance was measured by a four-terminal pair arrangement. Above 180 K, the resistivity is independent of frequency. At lower temperatures, the dielectric function could not be fitted by a Debye model with a single relaxation time, it should have a distribution. At T = 130 K, there is a sudden increase in the ρ – T relation, meanwhile an anomaly dielectric response occurs on the temperature dependant dielectric spectrum in the whole measured frequency range, in which the dielectric constant has a high value even at high frequency region. Our analysis suggests that the current system would be more consistent with the Zener polaron model. (condensed matter: electronic structure, electrical, magnetic, and optical properties)