Preparation and characterization of amorphous Cr2O3 nanoparticles obtained by solution plasma discharge

Abstract Amorphous chromium (III) oxide (Cr2O3) nanoparticles were synthesized by a solution plasma discharge procedure in CrCl3 aqueous solution. X–ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis were conducted to analyze the nanoparticles. Nanoscale Cr2O3 with good magnetic properties can be employed in information storage and spintronics. Therefore, the magnetic properties of the product were measured to assess their potential application. The results showed that the obtained Cr2O3 product was amorphous with a sheet-like morphology, in which small nanoparticles were attached to each other and wrapped by the water layer. Transmission electron microscopy results indicated that the covered particles produced in the CrCl3 solution were spherical with a mean diameter of 50 nm. The sheet-like morphology was converted into thinner slices when discharge electrolysis was conducted in the solution containing H2SO4. The amorphous phase could be transferred to nanocrystalline Cr2O3 with an average grain size of 100 nm after calcination at 600 °C. The Cr2O3 particles obtained in the H2SO4 solution became more uniform after heat treatment. The results of the magnetic property measurement showed that the Verwey transition and blocking temperatures of the produced Cr2O3 nanoparticles were 16 K and 66 K, respectively, and the separation of the zero-field-cooled curve and field-cooled curve occurred at 300 K. The magnetic properties of the nanoparticles were shown to be irreversible due to hysteresis. The formation process of amorphous Cr2O3 was proposed as 2Cr + 3H2O → Cr2O3 + 3H2 and 4Cr3+ + 6OH− + 6e– → 2Cr2O3 + 3H2.