Effect of disorder particles size of Nd on electrical transport on a bulk of Pr 2/3 Ba 1/3 MnO 3

Abstract

Polycrystalline samples of (Pr_{1– x} Nd _x )_0.67Ba_0.33MnO₃ with concentrations of x = 0.0, 0.167, 0.33, 0.5, 0.67, 0.833, and 1.0 have been prepared using solid-state reactions. The analysis of X-ray diffraction data revealed that all of the samples were found to crystallize in the orthorhombic structure. The electrical property, T_p, was determined by using standard four-point probe resistivity measurements in a temperature range of 30–300 K. A shift of the metal-insulator transition temperature, T_p, to a lower value was observed when Pr doping was increased. The electrical resistivity data was analyzed using various theoretical models, and it has been concluded that the resistivity of the samples in a low temperature regime (T < T_p) are well-fitted using the expression $\rho ={\rho }_0+{\rho }_2{T}^2+{\rho }_{4.5}{T}^{4.5}$ , implying the importance of grain/domain boundaries and electron–electron and two magnon scattering processes. In the high temperature regime (T > T_p), the resistivity data can be well described by small polaron hopping and variable range hopping mechanisms. In the semi-conducting portion, the activation energy (E_a) has been investigated. The E_a increased as the doping concentration increased. Scanning electron microscope micrographs showed that the substitution of Nd³⁺ ions for the Pr³⁺ site in LaBaMnO₃ leads to grain growth inhibition, disorder in the grain size, praseodymium segregation, and second phase formation.