Preparation And Characteration Of Multiferroic YMnO₃ Nanofibers By Electrospinning

Multiferroic materials have been formally defined as single phase materials which simultaneously possess two or more primary ferroic properties (ferroelectricity, ferromagnetism, ferroelasticity et al). Multiferroics not only possess one primary ferroic properties, but also have a number of new features by the coupling of the primary ferroic properties, which greatly develope its applied range. YMnO₃ exhibits simultaneously ferroelectricity and magnetism, which is a candidate for Metal- Ferroelectric- insulator-Semiconductor devices for its low electric conductivity, single polaxis, and nonvolatile elements. Studing on the synthesis and properties of the YMnO₃ thin films are one of the hot spot of researchers these days. However, there is quite a few reported on the one-dimensional nanostructures YMnO₃.For the intriguing properties, one-dimensional materials have broad application prospects in optical, composite, sensor, catalyst. Recently, various techniques have been developed to synthesize one-dimensional nanostructures. Among all these techniques, electrospinning is considered as a simple way to produce nanofibers, which are ultralong, aligned, the morphology and size controllable, since it price cheap, effect and simple operation. The multi-componets system nanofibers can be easy produced by electrospinning. The porous nanowire or nanotube which is a nonwoven porous material with large specific surface can be obtained via removal a component of the multi-componets nanofibers, and it has broader applications.In this study, YMnO₃ and Y_1-xCe_xMnO₃ inorganic nanofibers were synthesized by sol-gel preparation via electrospinning. The electrospun setup combined with four single crystal copper threads and a rotatable cylinder collector has been assembled to prepare the YMnO₃/PVP and Y_1-xCe_xMnO₃/PVP composite nanofibers. The main factors that affects electrospinning were researched through this experiment. Under the experimental conditions, the optimum nanofiber morphologies were observed for a 26 wt% concentration solution, a 15 kV electric field, a 10 cm distance between the spinneret tip and grounded collector and a 1000 rpm rotation speed of collector. The composite nanofibers which were prepared under the optimum electrospinning conditions, are smooth surface, arranged orderly and a rather uniform diameter around 150²00 nm over a length of several meters. The inorganic nanofibers which exhibited lotus-root-like morphology and surface-smooth, and have a reduced diameter ranging from70 to 100 nm over its length, can be obtained by different calcination temperature.The magnetism and ferroelectric properties of YMnO₃ and Y_1-xCe_xMnO₃ nanofibers were investigated by Vibrating sample magnetometer (VSM) and ferroelectric measurement system. The results showed that the hysteresis property was found at T=300 K, which indicated that H-YMnO3 nanofibers exhibited weak ferromagnetism. Perhaps this magnetic properties originated from the small size effect of H-YMnO₃ nanofibers, because normally the weak ferromagnetism is presented if the antiferromagnetic materials are nanoscale, the P–E curve revealed that the H-YMnO3 nanofibers possessed obvious ferroelectric properties. The remanent polarization, Pr of 9.83μC/cm²and the coercive electric field, Ec , of 30.42 kV/cm are obtained at 1000 Hz. Y_1-xCe_xMnO₃ nanofibers were also presented weak ferromagnetism and ferroelectric properties at room temperature.