Phase change, optical, and magnetic study of ball milled Cr-doped Al2O3 nanoparticles

Aluminium oxide's (Al 2 O 3 ) exceptional physical qualities make it an indispensable component of several technological systems. This work used the simple and very efficient mechanical ball-milling technique (MBMM) to manufacture γ-Al 2 O 3 powders doped with transition metal Cr (Al 2-x Cr x O 3 , x = 0.05 and 0.10). The impacts of these powders were compared and studied. Synthesizing metal oxide composites using MBMM is easy, cheap, and environmentally safe. A variety of characterization methods, including XRD, HRTEM with EDX, UV–vis–DRS, and VSM, were used to investigate the optical, structural, morphological, and magnetic properties of chromium (Cr) doped aluminium (Al 2 O 3 ) nanoparticles. The crystalline nature and proven hexagonal structure of the Cr-doped samples at 1100°C were validated by X-ray diffraction (XRD) patterns. In addition, the crystallite size decreased from 38.863 nm to 32.343 nm, and no sign of a secondary phase or phases was observed as the doping concentration increased. Results from morphological analyses in the 200 nm scanning range indicate that some of the nanoparticles are agglomerated, spherical, or hexagonal in shape. Results from energy-dispersive X-ray spectroscopy (EDX) show that the synthesised materials have the desired atomic ratios and that the elements Al, O, and Cr are present. A study using ultraviolet-visible-diffuse reflectance spectroscopy (UV-Vis-DRS) was conducted to examine the reflectance and optical band gap (Eg). A decrease in the optical band gap (Eg) from 4.303 eV to 4.210 eV was observed as the dopant concentration increased. At long last, the ferromagnetism and paramagnetism nature are shown by the behaviour of the magnetic hysteresis (M-H) curve for pure γ-Al 2 O 3 , pure Al 2 O 3 (1100°C), and Cr-doped samples. In addition, throughout the field range of ±3 T, the saturation magnetization increased from 0.0578 emu/g to 0.0794 emu/g. The stable phase of metal oxides (Al 2 O 3 ) was seen at γ-Al 2 O 3 (below 500°C) and α-Al 2 O 3 (1050°C-1100°C), in particular, because of temperature variation.