Role of Al2O3 in modulating the electrical transport behaviour of Pr0.67Sr0.33MnO3

Incorporating a secondary insulating phase into manganite compounds was anticipated to enhance their performance by modifying their magneto-transport properties. In this study, Pr0.67Sr0.33MnO3 (PSMO) was synthesised using the sol-gel approach, by varying the Al2O3 ratios to investigate their effect on structural and electrical transport behaviour. X-ray diffraction (XRD) analysis revealed that Al2O3 peak only appears at x = 0.10, indicating that Al2O3 segregate at grain boundaries rather than diffusing into the parent phase. The insulating nature of Al2O3 induce higher resistivity and lowers the metal-insulator transition temperature (TMI) in composite samples. Theoretical modelling reveals that grain boundaries effects dominate conduction at the metallic region, while small polaron hopping (SPH) and variable range hopping (VRH) models elucidate the transport mechanism in the insulating region. It was found that higher activation energy (EA) is needed for electron hopping in composite samples, resulting in a lower density of states at Fermi level (N(EF)). Furthermore, the resistivity data throughout the temperature range closely conform to the percolation model. Overall, this work highlights the influence of Al2O3 on the electrical transport behaviour of manganite composites and offers crucial insights into the interplay between structural and electrical properties in these manganite systems.

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