Abstract:
In this investigation, nanoparticles of B-site disordered Y2FeCrO6 (YFCO), Y2NiCrO6 (YNCO), and Y2CoCrO6 (YCCO) double perovskites were synthesized using a facile sol-gel technique to explore their structural, magnetic, and optical properties. YFCO and YCCO exhibited an orthorhombic structure within the pbnm space group, while YNCO displayed a monoclinic structure with a P21/n space group. The average nanoparticle sizes were 67 nm for YFCO and approximately 80 nm for YNCO and YCCO double perovskites. X-ray photoelectron spectroscopy revealed mixed valence states and oxygen vacancies, indicating antisite disorder (ASD) in all these three double perovskites. This disorder in YNCO and YCCO led to unconventional magnetic behaviors, such as a Griffiths-like phase observed through inverse susceptibility measurements, spanning from the ferromagnetic- like transition temperature to the Griffiths temperature. Additionally, YFCO exhibited negative magnetization with a compensation temperature around 170 K. The presence of a negative Curie-Weiss temperature and unsaturated magnetic hysteresis loops (up to 7 T) confirmed the coexistence of antiferromagnetic and weak ferromagnetic behavior in these materials. An exchange bias effect was observed in YFCO below its N´eel temperature, which could be tuned by applying a cooling magnetic field. Notably, both YFCO and YCCO exhibited a spontaneous exchange bias effect. The UV-visible spectra analysis indicated a semiconducting nature for YFCO, YNCO, and YCCO, with band gaps of 1.90 eV, 2.34 eV, and 1.35 eV, respectively. Moreover, YNCO was found to demonstrate potential as an electrode material for electrochemical supercapacitors, displaying a specific capacitance of 270 F g−1 at a current density of 0.5 A g−1 in a three-electrode system, and 180 F g−1 at 0.5 A g−1 in a symmetric two-electrode system. In the latter, an energy density of 6.25 Wh kg−1 was achieved at a power density of 250 W kg−1, using a mild 0.5 M neutral aqueous Na2SO4 solution as the electrolyte—an environmentally friendly alternative to the typically employed corrosive and concentrated alkaline solutions. The intriguing magnetic and charge storage properties of the B-site disordered YNCO double perovskite highlight its potential for use in spintronic devices and as efficient electrodes in symmetric hybrid supercapacitors.