Characterization of hollow BaTiO3 nanofibers and intense visible photoluminescence

Abstract

BaTiO3 hollow nanofibers were fabricated by electrospinning and then subsequent calcination of as-spun nanofibers with a heating rate of 2.5 °C/min. Scanning electron microscope and transmission electron microscope (TEM) results indicated that the heating rate had a significant effect on the morphology of the BaTiO3 hollow nanofibers. The X-ray diffraction, Raman spectroscopy, and TEM results indicate the prepared BaTiO3 hollow nanofibers have tetragonal phases. From the results of the X-ray photoelectron spectroscopy analysis, in the amorphous BaTiO3 nanofiber, peaks at 457.2 eV for Ti 2p3/2 were also found, which corresponded to the Ti3+ ions. However, in the crystalline BaTiO3 nanofibers, peaks of Ti 2p3/2 showed the Ti4+ ions. Intense visible photoluminescence was observed in the amorphous BaTiO3 nanofiber, which is calcined below a temperature of 500 °C. The observed intense photoluminescence was ascribed to a multiphonon process with localized states within the band gap of the highly disordered states. In the crystalline BaTiO3 hollow fiber, low intensity of photoluminescence showed at the visible region, which is originated from an intrinsic Ba defect.

Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

“…Peaks at 778 eV and 793.3 eV, respectively corresponding to the Ba 3d 5/2 and Ba 3d 3/2 , are assigned to the perovskite structure of BaTiO 3 . It is worth pointing out that the higher shoulders at 779.4 eV and 794.6 eV are usually associated with Ba vacancy point defects33. Note that the peak intensity at both 779.4 eV and 794.6 eV increases with the increase in Nd concentration, suggesting that Ba vacancy would boost with the introduction of Nd ions.…”

Magnetic and nonlinear optical properties of BaTiO3 nanoparticles

“…From the HRTEM images also clear that even at nanoparticle boundaries the particles is having clear lattice planes without any amorphous nature. In most of the chemical synthesis processes the crystallization temperature for BaTiO 3 is in the range of 600 o C-700 o C. 28,[37][38][39][40] Basically the higher temperatures are used for grain growth and densification in the sintering process.…”

Room Temperature Hydrogen Absorption of Mg/MgH2 Catalyzed by BaTiO3

“…The data plot for Ba 3d in the pure BaTiO 3 powder (Figure a) reveals its existence in two ferroelectric domains (F 1 and F 2 ) with characteristic binding energy peaks at ∼777.9 eV and ∼779.6 eV for 3d 5/2 . These ferroelectric domains describe the anomalous behavior of Ba 2+ and O 2– coordination (ranging from 12-fold in the bulk to <12-fold near the surface) in the layers of BaTiO 3 crystal during its synthesis. , The F 1 Ba ions in the bulk possess 12-fold oxygen coordination and are positioned at lower binding energy than the F 2 Ba ions lying near the surface with less oxygen coordination. Meanwhile, the Ba ions in BaCO 3 (a precursor in BaTiO 3 synthesis) possess 9-fold oxygen coordination at the same binding energy as with the F 2 domain Ba ions, hence, the binding energy at ∼779.6 eV could result from an overlap between the Ba ions in the F 2 domain and the adsorbed C–O species. , Previous studies have also shown that abrasive (grinding) and/or annealing processes could produce very reactive Ba ions near the surface of BaTiO 3 . − This may be the case in the observed spectra of the as-milled and dehydrogenated samples as shown in Figure b.…”