Role of oxygen vacancy and Fe–O–Fe bond angle in compositional, magnetic, and dielectric relaxation on Eu-substituted BiFeO3 nanoparticles

2014 ◽  
Vol 43 (15) ◽  
pp. 5731-5738 ◽  
Author(s):  
A. Tamilselvan ◽  
S. Balakumar ◽  
M. Sakar ◽  
Chiranjib Nayek ◽  
P. Murugavel ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Oxygen Vacancy ◽  
Dielectric Relaxation ◽  
Oxygen Vacancies ◽  
Bond Angle ◽  
Sol Gel ◽  
Bifeo3 Nanoparticles ◽  
Gel Technique ◽  
Dielectric Relaxation Behavior

The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol–gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C.

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.

Role of Catalyst on Refractive Index Tunability of Porous Silica Antireflective Coatings by Sol−Gel Technique

2007 ◽  
Vol 111 (23) ◽  
pp. 8291-8298 ◽  
Author(s):  
Abhilash Vincent ◽  
Suresh Babu ◽  
Erik Brinley ◽  
Ajay Karakoti ◽  
Sameer Deshpande ◽  
...  
Keyword(s):  
Refractive Index ◽  
Sol Gel ◽  
Porous Silica ◽  
Antireflective Coatings ◽  
Gel Technique

Photocatalytic degradation of indigo carmine by using tungsten doped bismuth vanadate

2021 ◽  
Vol 25 (7) ◽  
pp. 86-92
Author(s):  
Yasmin Ahmad ◽  
Suresh Ameta ◽  
Seema Kothari
Keyword(s):  
Photocatalytic Activity ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Sol Gel ◽  
Indigo Carmine ◽  
Bismuth Vanadate ◽  
Photogenerated Electrons ◽  
Gel Technique ◽  
Indigo Carmine Dye

The photocatalytic degradation of indigo carmine dye was studied using tungsten doped BiVO4. Bismuth vanadate powder has been synthesized by sol-gel technique. The incorporation of W ions into BiVO4 was confirmed by EDX. The photocatalytic activity was studied using different samples of BiVO4 by variation of pH, concentration of dye, dose of semiconductor and light intensity. It has been found that degradation of dye is more effective in presence of W doped BiVO4, It shows the role of tungsten ions for enhancing degradation of indigo carmine by reducing the recombination of photogenerated electrons and holes.

scholarly journals Dielectric Relaxation Behavior of BTO/LSMO Heterojunction

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1109
Author(s):  
Guoqiang Song ◽  
Yuanyuan Zhang ◽  
Sheng Li ◽  
Jing Yang ◽  
Wei Bai ◽  
...  
Keyword(s):  
Dielectric Relaxation ◽  
High Frequency ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Composite Films ◽  
Hysteresis Loops ◽  
Frequency Range ◽  
Magnetoelectric Composite ◽  
Polarization Switch

The BaTiO3 (BTO)/La0.7Sr0.3MnO3 (LSMO) magnetoelectric composite films were prepared by sol-gel method on STO (001) substrates. The heterojunction has highly preferred orientation and exhibits well ferroelectric properties with perfect hysteresis loops and microscopic polarization switch behaviors. The most interesting thing is the abnormal dielectric relaxation phenomenon in the dielectric spectra at high frequency range and around the phase transition temperature of LSMO. By analyzing the resistance properties of LSMO films, it is indicated that charge-based interfacial coupling, Maxwell-Wagner effect due to the JT polaron and fast resistivity rise in LSMO layer is the main reason. This work emphasizes the crucial role of resistivity exchanges and of carrier accumulation at interfaces for the application of magnetoelectric heterojunction.

scholarly journals Co-treatment of industrial air streams using A.O.P. and adsorption processes

2003 ◽  
Vol 5 (3) ◽  
pp. 167-174 ◽  
Author(s):  
P. Monneyron ◽  
A. De La Guardia ◽  
M. H. Manero ◽  
E. Oliveros ◽  
M. T. Maurette ◽  
...  
Keyword(s):  
Adsorption Equilibrium ◽  
Sol Gel ◽  
Photochemical Oxidation ◽  
Scanning Electronic Microscopy ◽  
Dynamic Experiments ◽  
Volatile Organic ◽  
Adsorption Processes ◽  
Gel Technique ◽  
Air Streams

Coupling adsorption with two different photochemical oxidation methods was investigated, in order to treat industrial gaseous effluents containing a low concentration of Volatile Organic Compounds (VOC). Prior to adsorption/photocatalysis cyclic study, newTiO2based catalysts were prepared by impregnating commercial zeolites in pellets form using a sol-gel technique. Scanning Electronic Microscopy observations linked to BET and adsorption equilibrium measurements of two VOC (1-butanol or BuOH and methyl-ethyl-ketone or MEK) showed thatTiO2happened to fix on the inert binder, without significant modification of support properties. A specific diffusion cell was used to produce dilute polluted air streams for each VOC in dynamic experiments, in which adsorption and photodegradation phases were alternatively carried out. Adsorption/photocatalysis co-treatment unable the total degradation of BuOH, and the regeneration of adsorbent. When using V-UV photolysis, pure zeolites were used, irradiated at 172 nm with an xenon excimer lamp. Excellent results were observed, since a total and rapid degradation was obtained for both VOC, especially thanks to a determining role of ozone.

Dielectric Behaviour Of BaTiO3 Prepared By Sol–Gel Technique When Exposed To Different Oxygen Concentrations

2012 ◽  
Author(s):  
Cheow Keat Yeoh ◽  
Srimala Sreekantan ◽  
Sabar Derita Hutagalung ◽  
Zainal Arifin Ahmad
Keyword(s):  
Dielectric Properties ◽  
Impedance Spectroscopy ◽  
Grain Boundary ◽  
Sol Gel ◽  
Chemical Processes ◽  
Oxygen Stoichiometry ◽  
Solution Ph ◽  
Gel Technique ◽  
Dta Curves ◽  
Oxygen Concentrations

Sifat dielektrik serbuk BaTiO3 yang disediakan melalui kaedah akues pada suhu rendah telah dikaji menggunakan kaedah spektroskopi impedans apabila didedahkan terhadap tahap oksigen yang berbeza. Untuk mengatasi masalah kebolehlarutan Ba dan Ti yang berbeza, nisbah sebatian Ba yang ditambah lebih tinggi daripada nisbah stoikiometri (tambahan 10%) dan nilai pH larutan yang tinggi (pH~13) diperlukan. Ujian XRD dan TGDTA menunjukkan BaTiO3 yang hampir tulen dapat disintesis melalui kaedah ini. Suhu pengkalsinan yang lebih tinggi menghasilkan darjah penghabluran bahan yang lebih tinggi. Kajian dielektrik menunjukkan bahan yang dihasilkan mengandungi lebih daripada satu elemen keelektrikan antaranya teras berkerintangan rendah, sempadan butiran berkapasitan tinggi dan suatu elemen pukal feroelektrik. Setelah didedahkan terhadap tahap oksigen yang lebih tinggi, nilai kerintangan sampel bertambah, yang mungkin disebabkan stoikiometri oksigen pada sampel yang diuji. Peningkatan dalam nilai kapasitan daripada sempadan butiran adalah lebih ketara jika dibandingkan dengan peningkatan unsur feroelektrik pukal. Kata kunci: Kaedah sol-gel, sintesis kimia, sifat dielektrik, BaTiO3 The dielectric properties of BaTiO3 powders prepared by a low temperature aqueous route when exposed to different oxygen concentrations have been studied by means of impedance spectroscopy. Due to the differences of solubility of Ba and Ti in aqueous solutions, deviations from stoichiometric ratios (a 10% excess) and higher solution pH (pH~13) were necessary. XRD traces and TG-DTA curves show the formation of nearly phase-pure BaTiO3 with higher calcinations temperatures promoting greater crystallinities. Dielectric measurements using impedance spectroscopy show the samples to consist of more than one electrical element including a low resistivity core, a high capacitance grain boundary and a ferroelectric bulk component. Exposing the samples to different oxygen concentrations caused a slight increase in resistivities with increasing oxygen concentration, which was attributed to the oxygen stoichiometry. A greater increase in the capacitance of the grain boundary component was also observed compared to the ferroelectric bulk. Key words: Sol-gel processes, chemical processes, dielectric properties, BaTiO3

scholarly journals Transition Metal B-Site Substitutions in LaAlO3 Perovskites Reorient Bio-Ethanol Conversion Reactions

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 344
Author(s):  
Quang Nguyen Tran ◽  
Olinda Gimello ◽  
Nathalie Tanchoux ◽  
Monica Ceretti ◽  
Stefania Albonetti ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Oxygen Vacancies ◽  
Sol Gel ◽  
Carbon Number ◽  
Ethanol Conversion ◽  
Ethanol Dehydration ◽  
Phase Conversion ◽  
Al Substitution ◽  
Dehydrogenation Of Ethanol

LaAlO3 perovskites, as such and with 25% molar Al substitution by Cu, Co, or Ga, have been prepared by sol-gel methods and tested as heterogeneous catalysts in the gas-phase conversion of ethanol. LaAlO3 presented a significant acidic character, with high formation of ethylene by ethanol dehydration. B-site substitutions increased the basicity of the catalysts, favoring the dehydrogenation of ethanol to acetaldehyde. The most reducible Cu- and Co-substituted materials, characterized by easier formation of surface oxygen vacancies, promoted the self-condensation of acetaldehyde by the Tishchenko mechanism, with formation of acetone and odd-carbon number products. Aldol coupling of acetaldehyde, favored on pure and Ga-substituted LaAlO3, led to the formation of butadiene and hexadiene. The role of Ga insertion, favoring both dehydrogenation of ethylene and dehydration of higher alcohols, corresponds to an amphoteric character. The formation of olefins and diolefins on all catalysts suggests that LaAl-based materials present the most acidic character among La-perovskites.

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