Papers by Author: Yan Hua Fan

Abstract: Theoretical study on the geometric structures and magnetic properties of small (FeAl)n (n=1-4) clusters has been carried out at the BPW91 level. In all the (FeAl)n clusters, the iron atoms are brought together, yielding a maximum of Fe-Fe bonds, and the aluminum atoms are located around a Fe core with a maximum of Fe-Al bonds which is different the bulk ordered FeAl alloy dominated by the Fe-Al bonds. As opposed to the bulk FeAl with non-magnetic, the small nano-clusters are highly magnetic moment dominated by Fe-Fe clustering.

Abstract: Ba0.7Sr0.3TiO3 (BST) thin films have been prepared on copper foils via sol-gel method in almost inert atmosphere containing different level of oxygen which was achieved by flowing high purified argon with the varied rate from 0.3 L/min to 2.0 L/min. X-ray diffraction pattern of the BST thin film exhibits dominant perovskite phase. SEM images reveal good crystallization and much dense structure of the thin film. The BST thin film annealed at almost inert atmosphere by flowing the high purified argon at the rate of 0.5 L/min, exhibits highest dielectric constants which are 1549.65 and 1350.86 at the frequency of 10 kHz and 1 MHz, respectively. Additionally, the film also shows optimized ferroelectric behavior and low leakage current density. The mechanism of the annealing atmosphere on properties of BST thin films was investigated.

Abstract: Ba0.7Sr0.3TiO3 thin films with a thickness of 300~900 nm were prepared with sol-gel method directly on the copper foils. The films have been processed in almost inert atmosphere such that the oxidation of Cu foil was avoided while allowing the film to crystallize. The crystal structure, morphology and dielectric properties of the films were measured and analyzed. The effects of annealing temperatures and film thickness on the electrical properties were discussed.