Structure, small polaron hopping conduction and relaxor behavior of Gd2NiMnO6 double perovskite

In this study, double perovskite Gd2NiMnO6 is prepared via auto-ignition method. Rietveld refinement of the XRD profile confirms the single phase monoclinic structure with space group P21/n. The cation Ni exhibits mixed valence state (+2/+4) and Mn exhibits +4 valence state. Grain, grain boundary and dc conductivity increase with temperature indicating the semi-conductive nature of the material. The grain conductivity is much higher and activation energy for grain conductivity is much lower than the grain boundary. The activation energy for dc conduction and hopping energy are almost identical at different temperature regions. The charge conduction mechanism follows non-overlapping small polaron tunnelling (NSPT) model. Different Mott's parameters confirm small polaron hopping. The polaron hopping mechanism is non-adiabatic in nature. Time-temperature superposition principle confirms the temperature independent nature of hopping mechanism. The value of electron photon coupling constant is 8.27 which confirms the strong electron-phonon coupling in this material. The dielectric relaxor behavior is found to follow modified Curie-Weiss law which becomes more conform with frequency. The value of co-efficient of diffuseness lies in the range 1.69-1.96 which confirms the diffuse behavior of the material.

Automated summary

In this study, double perovskite Gd2NiMnO6 was prepared via auto-ignition method, demonstrating semiconductor properties with higher grain conductivity compared to grain boundary conductivity. The charge conduction mechanism was found to follow the non-overlapping small polaron tunnelling model.