Effect of annealing on crystallinity and electrical properties of Bi1.5MgNb1.5O7 thin films

Abstract

Tunable dielectric materials have extensive applications in various fields; however, existing materials incorporate toxic elements or exhibit poor performance. Bi1.5MgNb1.5O7 (BMN), a Bi-based pyrochlore material, can potentially overcome these obstacles; however, it has not yet been fully characterized. In this study, the influence of annealing temperature on crystallinity and electrical properties of BMN thin films was investigated, and X-ray diffraction (XRD) results indicated that the BMN films exhibited a cubic pyrochlore structure. The surface roughness of the thin films significantly decreased and uniform grain growth was achieved after annealing at 600 °C. Interestingly, energy-level peaks corresponding to metallic Bi were found in the XPS spectra of the as-deposited BMN film. As the annealing temperature was increased to 300 °C, the metallic peak completely disappeared, providing crucial evidence for the improvement of the electrical properties of BMN after annealing. The BMN films prepared in this study exhibited significant dielectric relaxation, which is closely related to the occurrence of displacement disorder. The (442) plane identified via XRD serves as a characteristic feature of displacement disorder. The film annealed at 600 °C exhibited outstanding electrical properties, with an obtained dielectric constant, energy storage density, and tunability of 204, 1.44 J/cm3, 13.1 %, respectively. These results indicate that BMN has a strong potential for application in dielectric and energy storage devices.