One-step synthesis of yttrium orthoferrite nanocrystals via sol-gel auto-combustion and their structural and magnetic characteristics

Single phase yttrium orthoferrite (YFeO3) nanocrystals have been one-step synthesized by a sal gel auto-combustion method using nitrates of iron and yttrium as raw materials, citrate acid (CA) and ethylene glycol (EG) as chelating agents and nitrate ammonium as oxidant. The effects of CA/M and the pH value of the solutions on the concentrations of yttrium and iron citrate complex species were quantitatively studied to ensure the formation of chemically homogenous gels. The auto-combustion of the dried gels and the microstructural features and magnetic properties of as-synthesized YFeO3 nanocrystals were characterized and investigated by using XRD, FT-IR, TG-DTA, FESEM and VSM. It has been shown that a hexagonal YFeO3 can be formed during the auto-combustion of gels with CA/M = 1.5, EG/CA = 1.5, pH = 6.0 and Q = 35%, the molar ratio of the oxygen available from nitrates (NO3-) to the oxygen required for complete oxidation of fuels to CO2, H2O and N-2, while single phase orthorhombic YFeO3 nanocrystals of similar to 90 nm in average diameter may be one-step synthesized from the gels with Q = 80%, and show an enhanced weak ferromagnetism characterized with a RT magnetization of 0.45 emu g(-1) at the magnetic field 0.35T, a paramagnetism with the susceptibility chi = 2.27 x 10(-5) emu g(-1) Oe(-1), and an extremely low coercive field of 245 Oe. (C) 2012 Elsevier B.V. All rights reserved.