scholarly journals Impact of Reentrant Ferroelectric-tetragonal Phase on the Structure, Spectral, Electric, Magnetic and Magnetoelectric Properties of Gd3+-Fe3+ Co-substituted BaTiO3 Ceramics

2021 ◽  
Author(s):  
Esther Rubavathi P ◽  
Dhayanidhi D ◽  
Giridharan N.V. ◽  
Rahul M.T. ◽  
Nandakumar Kalarikkal ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Vacancy Concentration ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Data ◽  
Structural Effect ◽  
Oxygen Vacancy Concentration ◽  
Phase Conversion ◽  
Xps Spectra ◽  
Ferromagnetic Nature

Abstract The tetragonal reentrant phase conversion (P4mm) is obtained from the phase coexistence of the tetragonal and the non-polar hexagonal phases (P63/mmc) as a structural effect due to Gd substitution in Ba1-yGdyTi1-xFexO3(x=0.05; y=0.005, 0.01 and 0.015) ceramics. The diffraction spots in the SAED patterns and the d-spacing of the HREM lattice fringes mainly evidence the coexistence of the structural phase. Rietveld refinement offers the bond length and the other structural data. Ti presents itself as Ti3+ and Ti4+ whereas Fe presents as Fe2+ and Fe3+, revealed by the XPS spectra. The octahedra partly change to pentahedral due to the creation of the charge compensating the oxygen vacancies and therefore the conversion from tetragonal to hexagonal phase occurs. The EPR feature corresponding to Ti3+ decreases progressively as the Gd content increases, which implies a decrease of the oxygen vacancy concentration. This facilitates reentrant tetragonal phase conversion. The observed ferromagnetic nature originated from the Fe3+-O2--Fe3+ super-exchange and Gd3+-O2--Gd3+ interactions. The artificial single tetragonal phase magnetoelectric Ba0.985Gd0.015Ti0.95Fe0.05O3 material has the excellent magnetoelectric coupling coefficient of 3.74mV/cm.Oe.

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 Pathological transitions in myelin membranes driven by environmental and multiple sclerosis conditions

2018 ◽  
Vol 115 (44) ◽  
pp. 11156-11161 ◽  
Author(s):  
Rona Shaharabani ◽  
Maor Ram-On ◽  
Yeshayahu Talmon ◽  
Roy Beck
Keyword(s):  
Multiple Sclerosis ◽  
Phase Transition ◽  
Lipid Composition ◽  
Environmental Conditions ◽  
Structural Changes ◽  
Environmental Changes ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Modifications ◽  
Transition Points

Multiple sclerosis (MS) is an autoimmune disease, leading to the destruction of the myelin sheaths, the protective layers surrounding the axons. The etiology of the disease is unknown, although there are several postulated environmental factors that may contribute to it. Recently, myelin damage was correlated to structural phase transition from a healthy stack of lamellas to a diseased inverted hexagonal phase as a result of the altered lipid stoichiometry and low myelin basic protein (MBP) content. In this work, we show that environmental conditions, such as buffer salinity and temperature, induce the same pathological phase transition as in the case of the lipid composition in the absence of MBP. These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, we find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes. We postulate that these structural modifications result in myelin membrane vulnerability to the immune system attacks and thus can help explain MS etiology.

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

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.

Sign in / Sign up

Export Citation Format

Share Document