Temperature and Frequency Dependence of Negative Capacitance, Dielectric and Electric Properties in La_0.57Nd_0.1Sr_0.13Ag_0.2MnO₃ Ceramic

A detailed study of electrical and dielectric properties of the La_0.57Nd_0.1Sr_0.13Ag_0.2MnO₃ ceramic prepared by conventional solid-state reaction has been presented in this work. The frequency and temperature dependencies of capacitance (C–f–T) and conductance (G–f–T) of the sample were investigated in the frequency and temperature ranges of 40 Hz-110 MHz and 80 to 400 K, respectively. The C–f–T plot shows a phenomenon of negative capacitance (NC) which has been attributed to the blocking of charge carriers at the electrodes and the injection of minority carriers. Frequency and temperature dependencies of C and G show that these parameters are responsible for understanding conduction mechanism and charge transfer in materials. The frequency and temperature dependencies of dielectric properties such as the real and imaginary parts of permittivity (ε’, ε”), electrical modulus (M’, M”) and the real part of impedance (Z’) were obtained from the measurement of capacitance (C) and conductance (G) data. Negative dielectric constant is calculated from NC measurement, and it was attributed to the polarization effect. The ac conductivity versus frequency curve obeys to the Drude model. The ε’, ε”, tan δ and σ_ac show a dispersion at lower frequencies. From the electrical and dielectric measurements, the metal–semiconductor behavior was observed for the sample at a transition temperature of the order of 280 K.