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The impendence spectroscopy properties of polycrystalline Nd0.67Pb0.33Mn0.9Al0.1O3 perovskites prepared by sol–gel method at two different sintering temperatures (900°C and 1100°C), have been inves...

We have investigated the correlation between magnetocaloric and electrical properties of La0.47Pr0.2Pb0.33MnO3 perovskite prepared using the sol–gel method. Rietveld analysis of X-ray diffr...

The effect of Fe-doping at Mn-site on the structural and electrical properties of Nd0.67Ba0.33Mn1−xFexO3 (0 ≤ x ≤ 0.05) perovskites has been investigated. X-ray diffraction patterns show that the structural parameters change slightly due to the fact that the Fe3+ ions replacing the Mn3+ have similar ionic radius. The electrical properties of these samples have been investigated using complex impedance spectroscopy technique. a function of the frequency at different temperatures. When increasing the Fe-content, a decrease of dc conductivity was observed throughout the whole explored temperature range and the deduced activation energy values are found to increase from 128 meV for x = 0 to 166 meV for x = 0.05. The curves of the imaginary part of impedance (Z″) show the presence of relaxation phenomenon in our samples. The complex impedance spectra show semicircle arcs at different temperatures and an equivalent circuit of the type of Rg + (Rgb//Cgb) has been proposed to explain the impedance results.

We have investigated the effects of barium deficiency on structural, magnetic and magnetocaloric properties of La0.6Nd0.1Ba0.3−xMn0.9Cr0.1O3 (x = 0, 0.05 and 0.1) manganites prepared using the solid-state reaction. All the studied samples crystallize in the orthorhombic structure phase with Pnma space group. Magnetization versus temperature showed that the samples exhibit a second-order paramagnetic to ferromagnetic transition with a decrease of the Curie temperature (TC) from 275 K for x = 0–235 K for x = 0.1. The increase of barium deficiency leads to the decrease of the maximum magnetic entropy change ΔSMmax and relative cooling power values from (4.40 J.kg−1 K−1 and 262.94 J.kg−1, for x = 0) to (2.78 J.kg−1 K−1 and 159.41 J.kg−1, for x = 0.1) for an applied magnetic field μ0H = 5 T. These values are compared favorably with those of some other reported manganites, making our samples promising candidates for the magnetic refrigeration technology.

La0.33Sr0.67Mn0.33Ti0.67O3±δ perovskite was prepared by the standard solid state reaction at 1773 K. The sample crystallizes in the cubic Pm3-m structure. The electrical properties of the sample have been investigated above room temperature in 293–373 K range with varying frequency between 102 and 106 Hz using complex impedance analysis. The sample exhibit a metal–semiconductor transition temperature at TMS = 303 K. The conductance curves were well fitted by Jonscher power law G(ω) = Gdc + Aωn, which shows that with increasing temperature, the exponent (n) decreases below TMS, and increases above TMS. The activation energy deduced from the analysis of the conductance curves matches very well with the value estimated from the relaxation time indicating that relaxation process and electrical conductivity are attributed to the same defect. Nyquist plots of impedance show semicircle arcs for sample and an electrical equivalent circuit has been proposed to explain the impedance results.