Structural, dielectric, and magnetic properties of transition metals substituted strontium aluminates for energy storage applications

Group-II aluminates have a spinel structure widely used for energy storage purposes due to high thermal, chemical, and dielectric properties. These applications can be enhanced by the substitution of a small content of magnetic transition metals. In this study, M_xSr_1-xAl₂O₄ (where M = Mn, Fe, and Co and x = 0.1) compositions were successfully synthesized via a well-known hydrothermal technique. The uniform nano-sized sheets with the monoclinic structure without any impurity phase were confirmed by X-ray diffraction and field emission electron microscopy analysis. The qualitative and quantitative analysis studies reveal the presence of expected elements with their respective wt.% ratio observed through energy dispersive spectroscopy analysis. A clear non-magnetic and paramagnetic behavior with high saturation and remnant magnetization was observed from the M-H loop at room temperature for pure and transition metal (Mn, Fe, and Co) substituted Sr-aluminate samples. The highest values M_s, M_r, and H_c, i.e., 0.020 emu·g⁻¹, 0.005 emu·g⁻¹, and 0.026Oe are recorded for Co-doped SrAl₂O₄ composition. The dielectric studies reveal an increase in the value of the dielectric constant and a decrease in energy loss factor from 0.27 to 0.18 confirming the stability of the structure, and enhancement in ferroelectric parameters making these suitable candidates for energy storage applications.