Study of the structural, electric and dielectric proprieties of Bi1-xNdxMn2O5 (x=0, x=0.1 and x=0.2)

Abstract

Bi1-xNdxMn2O5 with (x = 0, 0.1 and 0.2) samples prepared by sol gel method, have been investigated for its structural and dielectrics properties. Crystallographic studies using X-ray diffraction and Rietveld Refinement techniques showed the formation of single-phase samples for all compositions, crystallizing in a mullite-type orthorhombic perovskite structure, space group Pbam (Z = 4). The SEM techniques confirmed the formation of single-phase materials with excellent mapping distribution. Scanning electron microscopy (SEM) revealed that the grains are irregularly spherical-like shaped confirmed the formation of single-phase materials with excellent mapping distribution, with mean sizes of 107, 103 and 92 for (x = 0, 0.1 and 0.2) respectively. The Dc conductivity expresses a semi-conductor dependence on temperature for the three samples all over the explored range of temperature. In addition to that, the substitution of Bi by Nd enhances the conductivity. The evolution of Dc conductivity versus temperature obeys to Mott and Davis law, which proves that the thermally activated small polaron hopping is the appropriate model of conduction at high temperature. Then it switches to variable range hopping at low temperature for BiMn2O5 and Bi0.9Nd0.1Mn2O5. The Ac conductivity is governed by the Jonsher law and its analysis shows that the correlated barrier hopping is the appropriate model of conduction for the two doped samples (Bi0.9Nd0.1Mn2O5and Bi0.8Nd0.2Mn2O5) while the overlapping large polaron tunneling is the suitable model for the undoped one. The impedance analysis is in good coherence with the conductivity analysis and emphasizes the undoubtedly contribution of grain boundaries in the transfer properties. Dielectric analysis allows to notice the heavy increase ofε’ with the increase of the mount of Nd. Besides, the evolution ofε’ with temperature suggest a relaxor behavior and is distinguished by the occurrence of peaks attributed to the existence of polar nanoregions.