Structural, electrical properties and complex impedance analysis of Pr_0.67Ba_0.22Sr_0.11Mn_1−xTi_xO₃ perovskites

The Pr_0.67Ba_0.22Sr_0.11Mn_1−xTi_xO₃ (x = 0.05 and 0.075) manganites are synthesized using solid-state reaction route. All XRD patterns with narrow and intense diffraction peaks reveal that the samples are well crystallized. For electrical properties we measure the conductivity versus temperature (80–400 K) and frequencies (40 Hz–10 MHz). These measurements were made by admittance spectroscopy technique. The effect of titanium doping on the electrical properties of our compounds appears by semiconductor behavior. The variation of DC-conductivity with temperature presents two metal–semiconductor transitions. The first transition T_MS bound by Mn³⁺/Mn⁴⁺ ratio but the second transition T_SM depends to an extrinsic effect of grain boundaries. It was observed also that the conductivity decreases with titanium concentration, such behavior is associated to a reduction of double-exchange mechanism. The conduction mechanism is explained by thermally activated hopping of small polaron at high temperature range. The activation energy was evaluated of about E_a = 30 m eV for x = 0.05 and E_a = 61 meV for x = 0.075. The total conductance spectrum of Pr_0.67Ba_0.22Sr_0.11Mn_0.925Ti_0.075O₃ compound is well described by the Jonscher power law: \(G\left(w\right)={G}_{dc }+A{\omega }^{n}\). Impedance study for the sample with x = 0.075 indicates the presence tow metal–semiconductor transitions and a non-Debye relaxation phenomenon related to a grain and grain boundary medium. Also, the modulation of the material by an electrical equivalent circuit show high values of grain boundary medium capacity.