Stabilization of the ferroelectric phase in Hf-based oxides by oxygen scavenging

2021 ◽  
Author(s):  
Mingji Su ◽  
Jirong Liu ◽  
Zeping Weng ◽  
Xiang Ding ◽  
Zhengyang Chen ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Crystallization Process ◽  
Ferroelectric Phase ◽  
Vacancy Concentration ◽  
Ferroelectric Properties ◽  
Ferroelectric Materials ◽  
Oxygen Vacancy Concentration ◽  
Vital Importance ◽  
Oxygen Scavenging

Abstract We propose an oxygen scavenging technique based on thermodynamic considerations of metal and oxygen systems to stabilize the ferroelectric phase and enhance the ferroelectricity in Hf-based oxides. By using an oxygen scavenging metal to control the oxygen vacancy concentration in Hf-based oxides, the effect of this oxygen scavenging technique in ferroelectric Hf-based oxides was systematically investigated. It was revealed that controlling the oxygen vacancies during the crystallization process is of vital importance to stabilizing the ferroelectric properties. This oxygen scavenging technique is an effective method of improving the performance of Hf-based ferroelectric materials without employing any dopant in HfO2.

MECHANISM STUDY ON OXYGEN VACANCY INDUCED RESISTANCE SWITCHING IN Au/LaMnO3/SrNb0.01Ti0.99O3

2013 ◽  
Vol 27 (11) ◽  
pp. 1350074 ◽  
Author(s):  
YU-LING JIN ◽  
ZHONG-TANG XU ◽  
KUI-JUAN JIN ◽  
CHEN GE ◽  
HUI-BIN LU ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Resistance Switching ◽  
Switching Behavior ◽  
Oxygen Vacancy Concentration ◽  
Mechanism Study ◽  
Switching Performance ◽  
Switching Characteristics

Mechanism of resistance switching in heterostructure Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 was investigated. In Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 devices the LaMnO 3 films were fabricated under various oxygen pressures. The content of the oxygen vacancies has a significant impact on the resistance switching performance. We propose that the resistance switching characteristics of Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 arise from the modulation of the Au / LaMnO 3 Schottky barrier due to the change of the oxygen vacancy concentration at Au / LaMnO 3 interface under the external electric field. The effect of the oxygen vacancy concentration on the resistance switching is explained based on the self-consistent calculation. Both the experimental and numerical results confirm the important role of the oxygen vacancies in the resistance switching behavior.

scholarly journals Evoked Methane Photocatalytic Conversion to C2 Oxygenates over Ceria with Oxygen Vacancy

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 196 ◽  
Author(s):  
Jin Du ◽  
Wei Chen ◽  
Gangfeng Wu ◽  
Yanfang Song ◽  
Xiao Dong ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Photocatalytic Oxidation ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Direct Conversion ◽  
Oxygen Vacancy Concentration ◽  
Ambient Conditions ◽  
Ethanol Production Rate ◽  
Viable Approach ◽  
Oxidation By Water

Direct conversion of methane to its oxygenate derivatives remains highly attractive while challenging owing to the intrinsic chemical inertness of CH4. Photocatalysis arises as a promising green strategy which could stimulate water splitting to produce oxidative radicals for methane C–H activation and subsequent C–C coupling. However, synthesis of a photocatalyst with an appropriate capability of methane oxidation by water remains a challenge using an effective and viable approach. Herein, ceria nanoparticles with abundant oxygen vacancies prepared by calcinating commercial CeO2 powder at high temperatures in argon are reported to capably produce ethanol and aldehyde from CH4 photocatalytic oxidation under ambient conditions. Although high-temperature calcinations lead to lower light adsorptions and increased band gaps to some extent, deficient CeO2 nanoparticles with oxygen vacancies and surface CeIII species are formed, which are crucial for methane photocatalytic conversion. The ceria catalyst as-calcinated at 1100 °C had the highest oxygen vacancy concentration and CeIII content, achieving an ethanol production rate of 11.4 µmol·gcat−1·h−1 with a selectivity of 91.5%. Additional experimental results suggested that the product aldehyde was from the oxidation of ethanol during the photocatalytic conversion of CH4.

Conversion of syngas into light olefins over bifunctional ZnCeZrO/SAPO-34 catalysts: regulation of the surface oxygen vacancy concentration and its relation to the catalytic performance

2021 ◽  
Author(s):  
Yaoya Luo ◽  
Sen Wang ◽  
Shujia Guo ◽  
Kai Yuan ◽  
Hao Wang ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Catalytic Performance ◽  
Light Olefins ◽  
Oxygen Vacancy Concentration ◽  
Surface Oxygen ◽  
Surface Oxygen Vacancy

Surface oxygen vacancies can improve the formation of methanol intermediates and promote their evolution into olefin products for syngas-to-olefins over Zn0.5CeZrOx/SAPO-34.

Prediction of Defects in PZT Thin Film Using Ab-Initio Method

2008 ◽  
Vol 32 ◽  
pp. 53-56
Author(s):  
Z. Zhang ◽  
L. Lu ◽  
P. Wu ◽  
C. Shu
Keyword(s):  
Oxygen Vacancy ◽  
Ab Initio ◽  
Lead Zirconate Titanate ◽  
Density Functional ◽  
Vacancy Concentration ◽  
Ferroelectric Properties ◽  
Density Functional Theory Calculations ◽  
Lead Zirconate ◽  
Oxygen Vacancy Concentration ◽  
A Site

This paper reviews our systematic and exhaustive studies on the lead zirconate titanate doped with dopants using ab initio density functional theory calculations in order to understand the mechanisms behind the dopings. Different candidates of dopants were selected by screening the periodical table of elements. In our studies, group VA, VIA elements (B-site donors), group IIA elements (A-site donors), group IIIB elements (B-site acceptors), and group VB elements (A-site donor, B-site acceptor/donors) are investigated as dopants in PZT. We found that there exist different mechanisms behind the improved ferroelectric properties, especially the fatigue behaviors. For donors doping, diluted oxygen vacancy concentration and reduced electronic suppression of polarization contribute to the fatigue-free behaviors of donor doped PZT. On the other hand, for acceptor doping, acceptor-oxygen-vacancy-acceptor clusters are energetically preferred, which greatly reduce the oxygen vacancy mobility and the domain pinning effects. We expect that this study could provide important information for the experiments on PZT-based materials.

Fluoride-capped nanoceria as a highly efficient oxidase-mimicking nanozyme: inhibiting product adsorption and increasing oxygen vacancies

Nanoscale ◽  
2019 ◽  
Vol 11 (38) ◽  
pp. 17841-17850 ◽  
Author(s):  
Yilin Zhao ◽  
Yawen Wang ◽  
Avi Mathur ◽  
Yaoqiang Wang ◽  
Vivek Maheshwari ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxidation Product ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Oxygen Vacancy Concentration ◽  
Highly Efficient

Fluoride capping prevents the oxidation product from inhibiting the CeO2 nanozyme, and increases the oxygen vacancy concentration for more efficient catalysis.

scholarly journals Influence of oxygen vacancy defects and cobalt doping on optical, electronic and photocatalytic properties of ultrafine SnO2-δ nanocrystals

2020 ◽  
Vol 14 (2) ◽  
pp. 102-112
Author(s):  
Zorana Dohcevic-Mitrovic ◽  
Vinicius Araújo ◽  
Marko Radovic ◽  
Sonja Askrabic ◽  
Guilherme Costa ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Uv Light ◽  
Vacancy Concentration ◽  
Blue Shift ◽  
Oxygen Vacancy Concentration ◽  
Cobalt Doping ◽  
Rutile Structure ◽  
Vacancy Defects ◽  
Co Doping

Ultrafine pure and cobalt doped SnO2-? nanocrystals (Sn1-xCoxO2-?, 0 ? x ? 0.05) were synthesized by microwave-assisted hydrothermal method. The as-prepared nanocrystals have single phase tetragonal rutile structure. With increase of Co content (x > 0.01), Co entered into SnO2 lattice in mixed Co2+/Co3+ state. Pronounced blue shift of the band gap with cobalt doping originated from the combined effect of quantum confinement and Burnstain-Moss shift. Raman and photoluminescence study revealed oxygen deficient structure of SnO2-? for which the prevalent defects are in the form of in-plane oxygen vacancies. Co-doping induced decrease of in-plane oxygen vacancy concentration and luminescence quenching. SnO2-? exhibited significantly better photocatalytic activity under UV light irradiation, than Co-doped samples due to better UV light absorption and increased concentration of in-plane oxygen vacancies which, as shallow donors, enable better electron-hole separation and faster charge transport.

scholarly journals Combined iDPC and EELS analyses for quantifying oxygen vacancy concentration in LSMO

2021 ◽  
Vol 27 (S1) ◽  
pp. 1196-1197
Author(s):  
Aubrey Penn ◽  
Sanaz Koohfar ◽  
Divine Kumah ◽  
James LeBeau
Keyword(s):  
Oxygen Vacancy ◽  
Vacancy Concentration ◽  
Oxygen Vacancy Concentration

scholarly journals Effects on Microstructure and Ionic Conductivity of the Co-Doping with Strontium and Samarium of Ceria with Constant Oxygen Vacancy Concentration

Solids ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 341-370
Author(s):  
Toby Sherwood ◽  
Richard T. Baker
Keyword(s):  
Oxygen Vacancy ◽  
Grain Boundary ◽  
Vacancy Concentration ◽  
Synthesis Method ◽  
Ionic Conductivities ◽  
Solubility Limit ◽  
Material Structure ◽  
Oxygen Vacancy Concentration ◽  
Co Doping ◽  
Phase Pure

Partially substituted cerias are attractive materials for use as electrolytes in intermediate-temperature solid oxide fuel cells (SOFCs). Ceria doped with Sm or Gd has been found to have high ionic conductivities. However, there is interest in whether doping with multiple elements could lead to materials with higher ionic conductivities. The present study looks at the effects of co-doping Sr and Sm in ceria. A compositional series, Ce0.8+xSm0.2−2xSrxO2−δ (with x = 0–0.08), designed to have a constant oxygen vacancy concentration, was successfully prepared using the citrate–nitrate complexation method. A solubility limit of ~5 cation% Sr was found to impact material structure and conductivity. For phase-pure materials, with increasing Sr content, sinterability increased slightly and intrinsic conductivity decreased roughly linearly. The grain boundaries of phase-pure materials showed only a very small blocking effect, linked to the high-purity synthesis method employed, while at high %Sr, they became more blocking due to the presence of a SrCeO3 impurity. Grain capacitances were found to be 50–60 pF and grain boundary capacitances, 5–50 nF. The variation in the bulk capacitance with Sr content was small, and the variation in grain boundary capacitance could be explained by the variation in grain size. Slight deviations at high %Sr were attributed to the SrCeO3 impurity. In summary, in the absence of deleterious effects due to poor microstructure or impurities, such as Si, there is no improvement in conductivity on co-doping with Sr and Sm.

Magnetic State of Ba-Doped Manganites Depending on the Oxygen Vacancy Concentration

2002 ◽  
Vol 233 (2) ◽  
pp. 321-330 ◽  
Author(s):  
S.V. Trukhanov ◽  
N.V. Kasper ◽  
I.O. Troyanchuk ◽  
H. Szymczak ◽  
K. B�rner
Keyword(s):  
Oxygen Vacancy ◽  
Magnetic State ◽  
Vacancy Concentration ◽  
Oxygen Vacancy Concentration ◽  
Doped Manganites
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