Ailin Xia

Facile preparation of Mn-doped CeO2 Submicrorods by composite-hydroxide-salt-mediated approach and their magnetic property

Mn-CeO2 submicrorods have been obtained from anomalous CeO2 particles though a novel composite-hydroxide-salt-mediated (CHSM) approach. This method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide-salt eutectic at ~225 oC and normal atmosphere without using an organic dispersant or capping agent. The magnetic measurement of the Mn-CeO2 submicrorods exhibits an enhanced ferromagnetic property at room temperature with a remanence magnetization (Mr) of 1.4 × 10-3 emu.g-1 and coercivity (Hc) of 75 Oe. The UV-visible spectra reveal that the absorption peak of the CeO2 shifts from ultraviolet region to visible light region after being doped with Mn ions. The room temperature ferromagnetic properties and light absorption of the Mn-CeO2 submicrorods would have wide applications in spintroics and photocatalysis field.

Synthesis and magnetic properties of hydrothermal magnesium–zinc spinel ferrite powders

Mg–Zn ferrite powders with the nominal composition Mg0.5Zn0.5Fe2O4 were synthesized via hydrothermal method, and their synthesis, magnetic properties and microstructures were studied. It was found that the pH value affected the amount of impurity Fe2O3 and the purity of ferrites greatly. It was also found excess Zn content (5 at.%) in starting materials was not helpful to synthesize pure spinel ferrite, while the prolonged reaction time was harmful for the formation of pure spinel structure. The specimens presented small coercivityxa0lower than 10xa0Oe, which showed a typical magnetically soft behavior. With the increase of pH value, the saturation magnetization of specimensxa0with excess Zn ions (5xa0at.%) kept increasing from 23.90 to 41.82xa0emu/gxa0due to the decreasing amount of impurity Fe2O3. The study of microstructures showed that the large particles in powders were the aggregates of small nanoscale crystallites. The analysis of actual Zn and Mg content in synthesized ferritesxa0confirmedxa0that the best experimental conditions for synthesis of pure spinel Mg–Zn ferrite are the hydrothermal temperature is 200xa0°C, the reaction time is 8xa0h, the pH value is 12 and the excess amount of Zn(NO)3 in starting materialsxa0is 5 at.%.

Microstructure and magnetic transition in Cr-substituted Mg–Zn spinel ferrite powders prepared via hydrothermal method

Mg–Zn ferrite powder specimens with the nominal composition Mg0.5Zn0.5CrxFe2−xO4 (xxa0=xa00.0–1.0 with steps of 0.2) were synthesized via hydrothermal method. It is found that all the specimens exhibit a typical spinel structure, and the lattice parameter increases slightly with x, which confirms the substitution of Cr3+ for Fe3+. The average crystallite size first increases but then decreases with x, which is not the same as the results in previous reports on spinels. The particles in specimens are the aggregate of small nanoscale crystallites, and roughly aggregate more extensively with the increasing Cr content. With the increase of x, the saturation magnetization decreases rapidly, and it becomes more and more difficult for the specimens to magnetize to saturation. The increase of coercivity from 0.6 (xxa0=xa00.0) to 32.3xa0kAxa0m−1 (xxa0=xa01.0) shows a transition from a typical soft magnetic behavior to a hard magnetic behavior with the increase of Cr content, which was not reported before.

Structural and magnetic properties of spinel (Co,Cu)Fe2O4 ferrites prepared via a hydrothermal and sintering process

Spinel Co–Cu ferrites with the nominal composition Co1−xCuxFe2O4 ferrites (xxa0=xa00.0–0.4 with steps of 0.1) were prepared by a hydrothermal and sintering process, and the structural and magnetic properties of as-synthesized and sintered powder specimens were compared by using X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometry and vibrating sample magnetometer analyses. It is found that all the as-synthesized and sintered specimens are single phase, and only suitable amount of Cu2+ substitution (xxa0≤xa00.3) is favorable for the growth of grains at high sintering temperature. In addition, with the increase of x, the saturation magnetization of both the as-synthesized and sintered powders decreases continuously, while the coercivity exhibits a first increasing but then decreasing tendency.

Li-Cr substituted nickel-zinc-copper ferrite powders: structural and magnetic properties

Abstract Li–Cr substituted NiZnCu ferrite powder specimens with the nominal composition Ni0.25–2xLixCrxCu0.15Zn0.6Fe2O4 (x=0.00, 0.01, 0.02, 0.03, 0.04) were prepared primarily via chemical coprecipitation. X-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry were used to study their structural or magnetic properties. It is found that all the specimens exhibit a single phase after annealing. The variation tendency of saturation magnetization with x exhibts a strange variation tendency and can be attributed to the different site occupation of Li+ions. It is also found that suitable Li–Cr substitutions help decrease the annealing temperature.

Structural and magnetic properties of Li–Al-substituted Ni–Zn–Cu ferrite powders prepared via chemical coprecipitation method

Li–Al substituted Ni–Zn–Cu ferrite powder specimens with the nominal composition Ni0.25−2xLixAlxCu0.15Zn0.60Fe2O4 (xxa0=xa00.00, 0.01, 0.02, 0.03, 0.04) were prepared via an improved chemical coprecipitation method. An X-ray diffractometer, a scanning electron microscope and a vibrating sample magnetometer were used to study their structural and magnetic properties. It is found that all the specimens exhibit typical single-phase spinel structures after annealing, and the saturation magnetization decreases with increase of x. The initial susceptibility first increases but then decreases, and obtains the maximum when xxa0=xa00.02, which shows the proper content of Li–Al substitutions is favourable for the increase of initial susceptibility. It is also found that the Li–Al substitutions affect the grain growth slightly.