Electrical conductance and complex impedance analysis of La_0.6Pr_0.1Ba_0.3Mn_1-xNi_xO₃ nanocrystalline manganites

We have investigated the electrical properties of La_0.6Pr_0.1Ba_0.3Mn_1-xNi_xO₃ (x = 0 and x = 0.1) nanocrystalline manganites using complex impedance spectroscopy technique in 40Hz-10 kHz and 80-320 K, frequency and temperature ranges, respectively. The two samples exhibit a metal-semiconductor transition temperature T_MS which decreases from 160 to 120 K when increasing Ni content from x = 0 to x = 0.1. The total conductance curves for samples are found to obey Jonscher power law G(ω) = G_DC + Aω ⁿ. The Ni content affects the activation energy (E_a) which increases from 37 meV for x = 0 to 48 meV for x = 0.1. The obtained n exponent values for x = 0 are higher than those obtained for x = 0.1. This can be related to the decrease in grain size when Ni content increases. Nyquist plots of impedance show semicircle arcs for samples, and an electrical equivalent circuit has been proposed to explain the impedance results. (orig.)