Investigation of structural, electrical and dielctrical properties of Pr_0.67Ba_0.22Sr_0.11Mn_1−xFe_xO₃ (0 ≤ x ≤ 0.2) perovskite

In the present work, we have studied the structural, electrical and dielectrical properties of Pr_0.67Ba_0.22Sr_0.11Mn_1−xFe_xO₃ (0 ≤ x ≤ 0.2) materials prepared through the solid state reaction. This study has been performed using admittance spectroscopy technique over a wide range of temperatures (80–340 K) and frequencies (40 Hz–10 MHz). The variation of conductivity with temperature shows a metal–semiconductor transition for x = 0 and 0.05. A semiconductor behavior is noticed for the others compositions. The transition temperature T_MS was found to be about 220 and 90 K for samples with x = 0 and 0.05, respectively. It is also found that the conductivity decreases with Fe concentration, such behavior is related to a reduction of double exchange mechanism. The conduction mechanism is described by thermally activated hopping of small polaron. The activation energy of such process is sensitive to the iron concentration. This energy increases with increasing Fe content from E_a = 22 meV for x = 0 to E_a = 67 meV for x = 0.20. The dielectric permittivity as function of the temperature is characterized by the appearance of dielectric transition which is described by the Curie–Weiss law. The dielectric transition temperature T_d change with the iron concentration and it is found to be 100, 170, 140 and 180 K for x = 0.05, 0.10, 0.15 and 0.20, respectively.