Impact of trivalent Yttrium on the structural and optical properties of CaAl₂O₄: New frontier in supercapacitor positive electrode

In this work, trivalent Yttrium doped calcium aluminate (CaAl₂O₄:x% Y³⁺) were synthesized for the first time. Through Photoluminescence (PL) spectroscopy and Commission Internationale de l'Eclairage (CIE), CaAl₂O₄:0.1 % Y³⁺ has demonstrated to be a potential high emitting phosphor material amongst other high concentration Y³⁺ doped samples, emitting a vibrant blue – pink hue where others are emitting a transiting hue from blue to green within a white vertex region. FTIR and UV–Vis have confirmed the prepared material and the presence of Y dopant. The SEM showed insignificant morphological change and the presence of pores, which were quantified using BJH and DFT methods to be micro – and meso–pores. Moreover, CaAl₂O₄ is also being reported as a positive electrode in supercapacitors for the first time. The analysis shows that it has superior performance within 1 M KOH electrolyte, with a specific capacity of 47.71 mA h g⁻¹ at 1 A g⁻¹ and a maximum power of 39.68 kW kg⁻¹. Trasatti's method showed a surface (138 Fg^-1) and diffusion (695 Fg^-1) contribution ratio of 17:83 (%) of the total stored energy. It has a capacity retention and columbic efficiency of 100 % at the end of 10 000 cycles, which was achieved via utilization of all micropores reaction sites. The EIS showed a small solution resistance of 0.75 Ω, indicating high ionic conductivity and a phase angle of – 50 °. Thus, these results show that CaAl₂O₄ is a potential candidate for photoluminescence and energy storage application.