Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO₃

Abstract

In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La 0.1 Sr 0.9 TiO 3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material's surface. In addition, a high concentration of O − defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics.

Photocatalytic Deacon Reaction over SrTiO3

“…Two different Sr species were distinguished, assigned to bulk Sr (Figure 5, left, red) and surface Sr (Figure 5, left, blue). The presence of a surface Sr species was reported before by Mascotto et al, [23,24] who describe the intrinsic segregation of Sr to the surface of SrTiO 3 which is supported by the Sr/Ti ratios > 1 (Table ST1) derived for all samples. From the chemical point of view, bulk Sr corresponds to SrTiO 3 , whereas surface Sr may be present as SrO, Sr(OH) 2 or undercoordinated Sr. [23] It is likely that these less coordinated and more easily accessible Sr surface species are converted to SrCl 2 more easily than SrTiO 3 .…”

Understanding Oxygen Release from Nanoporous Perovskite Oxides and Its Effect on the Catalytic Oxidation of CH4 and CO

“…The signals at 529 eV and 531 eV belong to the lattice oxygen and to hydroxides/chemisorbed oxygen, respectively 29 . A contribution at 533 eV is characteristic for physically adsorbed oxygenated species 36,37 (e.g. water) and was detected only in GLY-STF35.…”

Flash Sintering of YSZ/Al2O3 Composites: Effect of Processing and Testing Conditions

“…Such amazing effect, which changes the sintering time form 10 4 s to 10 1 s range, has attracted a relevant scientific interest aiming at unraveling the physical and chemical mechanisms behind the phenomenon [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Although definitive conclusions cannot be drawn yet, the mainstream is that the process is predominantly driven by the Joule effect coupled with side field/current-induced athermal phenomena [ 23 ] which can be possibly use to develop ceramics with new functional [ 24 , 25 , 26 , 27 ] and mechanical [ 28 ] properties. On the other hand, several researchers focused on the application of the process to different class of ceramics employing commercially-available spark plasma sintering [ 26 , 29 , 30 , 31 , 32 ] and microwave sintering [ 33 , 34 ] equipment.…”