Pure and Mn-doped barium titanate nanofibers were synthesized by the electrospinning method. The morphology, microstructure and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy and transmission electron microscopy. After annealing at 850°C, we obtain nanofibers a few μm long, formed by nanoparticles of irregular shape with sizes around 100 nm. X-ray diffraction and Raman spectroscopy show that a partial phase transition from tetragonal to hexagonal takes place for BaTi 0.90 Mn 0.10 O 3 . Vibrational phonon modes were calculated for BaTiO 3 within the density functional theory (DFT) framework. Ferroelectricity has been probed on pure and Mn-doped BaTiO 3 nanofibers, by means of piezoresponse force microscopy in an atomic force microscope, confirming the polar domain switching behavior of the fibers. The measured piezoelectric coefficient d 33 were 31 and 22 pm/V for BaTiO 3 and BaTi 0.90 Mn 0.10 O 3 . Magnetic properties of the samples were probed in a superconducting quantum interference device. Diamagnetic and paramagnetic behaviors were found in pure and Mn-doped samples, respectively. K E Y W O R D S atomic force microscopy, barium titanate, electrospinning, ferroelectricity/ferroelectric materials, perovskites

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Over the last few decades, one dimensional nanomaterials such as nanotubes and nanofibers, have attracted great attention due to their unique structure and properties, i.e. large specific surface area and chemical/mechanical stabilities. Thus nanofibers can be used as building blocks in nanotechnology [1,2]. Previously, several ceramic nanofibers have been synthesized by various processes, e.g. solution method, laser ablation, chemical vapor deposition (CVD), sol-gel, hydrothermal method and mechanochemical activation. On the other hand, electrospinning has been recognized as an efficient technique to make polymeric nanofibers [3]. Recently, there has been an intense research effort on electrospinning of ceramics since it is a straightforward way to synthesize nanostructures.Barium titanate, BaTiO3 (BT) is widely used as dielectric material in ceramic capacitors [4], it is also one of the extensively studied ferroelectric material with wide range of applications in non-volatile ferroelectric random access memories, as transducers, sensors and actuators, etc [5].The synthesis of pure and Mn-doped BaTiO3 nanofibers, were synthesized by the electro-spinning technique. A detailed description of the procedure can be found in the literature [6]. In this work, the precursor solution was composed by poly(vinylpyrrolidone) (PVP), barium acetate Ba(C2H3O2)2, titanium isopropoxide Ti[OCH(CH3)2]4 and manganese acetate Mn(C2H3O2)2 dissolved in ethanol/acetic acid. The solution was heated at 25°C with stirring for 5 hours and then delivered into a metallic needle at a constant flow rate of 0.3 mL/h by a syringe pump. The metallic needle was connected to a high-voltage power supply and a grounded aluminum foil was placed 15 cm from the needle tip.With an applied high-voltage of 15 kV, the precursor solution jet was accelerated toward the aluminum foil, leading to the formation of Ba(C2H3O2)2/Ti[OCH(CH3)2]4/Mn(C2H3O2)2/PVP fiber composite, together with a rapid evaporation of the ethanol. The composite nanofibers were then annealed 2 h at 850 °C, with a heating rate of 3°C/min, at the end of the thermal cycle, BaTiO3 and BaTi1-xMnxO3 nanofibers were obtained.The presence of a pure phase is confirmed by XRD analysis, as shown in Fig. 1, for calcined fibers, showing the formation of crystalline BaTiO3. Figs. 2 and 3 show the XRD patterns from BaTi0.95Mn0.05O3 and BaTi0.95Mn0.05O3, respectively. In these patterns was observed the presence of additional signal from (103) and (203) planes, it is expected that they are from a Mn compound. Fig. 4 shows a SEM micrograph of as-spun fibers. Cylindrical and randomly oriented fibers with diameter about 30-250 nm were obtained. Fig. 5 shows a TEM micrograph from isolated and calcined BaTiO3 nanofibers. In this Figure, it can be observed fibers with few µm in length and an irregular morphology. Fig. 6 shows TEM micrograph from doped sample, different surface morphology is evident. Deeper characterization by TEM on fiber with different concentration are carried-out References:1920

Pure and Mn-doped lithium tantalate nanofibers, with Mn concentrations of 1%, 2.5%, and 5%, were synthesized by the electrospinning method. The morphology, microstructure, and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Raman spectroscopy has shown to be a powerful tool to detect either local variations or changes of the whole structure. Position and width of one Raman line can be used as markers of a structural change. Some vibrational modes are especially associated with the site of Li or Ta ions and so, they can be affected by the introduction of dopant ions. Any damages or local changes in the microstructure can be detected by a line broadening.With the use of Raman spectroscopy, the sites where Mn ions enter the doped structures were established by recording the shift and broadening of peaks in Mndoped structures with respect to pure lithium tantalate. Thus it was proven that Mn ions enter the Li sites for low Mn concentration and, on the other hand, for higher concentrations, the dopant substitutes Li and Ta sites. First-principles calculations were performed within the density functional theory, including latticedynamic calculations of the phonon modes at the zone center (Γ point), for the pure structure, to find the irreducible representation of the modes.