scholarly journals Effect of A-Site Nonstoichiometry on Defect Chemistry and Electrical Conductivity of Undoped and Y-Doped SrZrO3

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1258 ◽  
Author(s):  
Liliya Dunyushkina ◽  
Adelya Khaliullina ◽  
Anastasia Meshcherskikh ◽  
Alexander Pankratov ◽  
Denis Osinkin
Keyword(s):  
Electrical Conductivity ◽  
Zirconium Oxide ◽  
Relaxation Times ◽  
Secondary Phase ◽  
Solubility Limit ◽  
Defect Chemistry ◽  
Total Conductivity ◽  
Strontium Zirconate ◽  
X Ray ◽  
A Site

The effect of Sr-nonstoichiometry on phase composition, microstructure, defect chemistry and electrical conductivity of SrxZrO3−δ and SrxZr0.95Y0.05O3−δ ceramics (SZx and SZYx, respectively; x = 0.94–1.02) was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and impedance spectroscopy followed by distribution of relaxation times analysis of impedance data. It was shown that at low Sr deficiency (x > 0.96 and 0.98 for SZx and SZYx, respectively) a solid solution of strontium vacancies in strontium zirconate crystal structure forms, whereas at higher Sr deficiency the secondary phase, zirconium oxide or yttrium zirconium oxide, is precipitated. Yttrium solubility limit in strontium zirconate was found to be close to 2 mol%. Y-doped strontium zirconates possess up to two orders of magnitude higher total conductivity than SZx samples. A-site nonstoichiometry was shown to have a significant effect on the electrical conductivity of SZx and SZYx. The highest total and bulk conductivity were observed at x = 0.98 for both systems. Increasing the conductivity with a rise in humidity indicates that proton conduction appears in the oxides in wet conditions. A defect model based on consideration of different types of point defects, such as strontium vacancies, substitutional defects and oxygen vacancies, and assumption of Y ions partitioning over Zr and Sr sites was elaborated. The proposed model consistently describes the obtained data on conductivity.

Solubility Limit of Sol–Gel Grown Nano Zn1-xMgxO Through Charge Density Distribution

2013 ◽  
Vol 68 (10-11) ◽  
pp. 668-676
Author(s):  
Santhanam Francis ◽  
Ramachandran Saravanan ◽  
Mohammed Açıkgöz
Keyword(s):  
Zinc Oxide ◽  
Density Distribution ◽  
Electron Density ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Secondary Phase ◽  
Solubility Limit ◽  
Host Lattice ◽  
Wurtzite Phase ◽  
X Ray

The mixed oxides Zn1-xMgxO were prepared as polycrystalline powders with various compositions (x = 0:02, 0.04, 0.05, and 0.10) using sol-gel technique. X-ray diffractometer (XRD) was used to characterize the powders for structural and electronic properties. X-ray diffraction analysis reveals that all the prepared samples exhibit the single wurtzite phase of zinc oxide (ZnO), and magnesiumdoping does not induce any secondary phase in the samples. The Bragg peak positions in the XRD patterns are found to be shifted towards higher 2q values with more addition of magnesium in the zinc oxide lattice. Magnesium addition in the zinc oxide lattice is found to enhance the mid bond electron density distribution up to x = 0:05 and then decrease for x = 0:10. Evidence of host lattice as well as interstitial addition of Mg2+ ions has been realized for x = 0:10, through electron density analysis.

scholarly journals Mechanochemical synthesis and electrical conductivity of nanocrystalline δ-Bi2O3 stabilized by HfO2 and ZrO2

2009 ◽  
Vol 74 (12) ◽  
pp. 1401-1411 ◽  
Author(s):  
Miodrag Zdujic ◽  
Dejan Poleti ◽  
Cedomir Jovalekic ◽  
Ljiljana Karanovic
Keyword(s):  
Electrical Conductivity ◽  
Zirconium Oxide ◽  
Molar Ratio ◽  
Mechanochemical Reaction ◽  
Dsc Analysis ◽  
X Ray ◽  
Fluorite Type ◽  
Milling Medium ◽  
20 Nm ◽  
Milling Tools

A powder mixture of ?-Bi2O3 and HfO2, in the molar ratio 2:3, was mechanochemically treated in a planetary ball mill under air, using zirconium oxide vials and balls as the milling medium. After 50 h of milling, the mechanochemical reaction led to the formation of a nanocrystalline ?-Bi2O3 phase (fluorite-type solid solution Bi0.78Hf0.59Zr0.63O3.61), with a crystallite size of 20 nm. The mechanochemical reaction started at a very beginning of milling accompanied by an accumulation of ZrO2 arising from the milling tools. The samples prepared after various milling times were characterized by X-ray powder diffraction and DSC analysis. The electrical properties of the as-milled and pressed Bi0.78Hf0.59Zr0.63O3.61 powder were studied using impedance spectroscopy in the temperature range from 100 to 700?C under air. The electrical conductivity was determined to be 9.43?10-6 and 0.080 S cm-1 for the temperatures of 300 and 700?C, respectively.

Effects of Second Phase and Defect on Electrical Properties in Bi0.5Na0.5-xKxTiO3 Lead-Free Piezoelectric Ceramics

2011 ◽  
Vol 284-286 ◽  
pp. 1343-1348
Author(s):  
Pin Yi Chen ◽  
Cheng Sao Chen ◽  
Chen Chia Chou ◽  
Tseung Yuen Tseng ◽  
Haydn Chen
Keyword(s):  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Defect Formation ◽  
Secondary Phase ◽  
Second Phase ◽  
Valence Transition ◽  
X Ray ◽  
Potassium Titanate ◽  
A Site ◽  
Li Substitution

Second phase and defect formation mechanism of (Bi0.5(Na1-xKx)0.5)TiO3 (BNKT100x) ceramics were investigated using electron microscopy, x-ray photoelectron spectroscope (XPS) and electrical properties measurements. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within matrix due to thermodynamic stability of potassium titanate. Ti valence transition for BNKT ceramics sintered in air might be ascribed to formation of the secondary phase, rather than simply attributed to volatilization of bismuth. Li substitution at A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate Li doped BNKT ceramics suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current.

scholarly journals Effects of barium substitution on the sintering behavior, dielectric properties of Ca2Nb2O7 ferroelectric ceramics

2017 ◽  
Vol 07 (02) ◽  
pp. 1750013 ◽  
Author(s):  
Chunchun Li ◽  
Huaicheng Xiang ◽  
Yuandong Qin ◽  
Liang Fang
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Secondary Phase ◽  
Solubility Limit ◽  
Ferroelectric Ceramics ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Spectroscopy Analysis ◽  
X Ray

Barium-doped Ca2Nb2O7 ceramics were prepared in the form of Ca[Formula: see text]BaxNb2O7 (0 [Formula: see text] 0.6) by solid-state reaction. The solubility limit of barium in Ca2Nb2O7 was found to be [Formula: see text] based on X-ray diffraction and Raman spectroscopy analysis. When [Formula: see text] 0.4, Ca[Formula: see text]BaxNb2O7 solid solutions with a monoclinic perovskites-like layered structure (PLS) were formed, whereas beyond [Formula: see text], a secondary phase CaNb2O6 was detected. The dielectric properties obviously depended on the barium substitution. With increasing barium amount, the dielectric constant increased from 33.5 for pure Ca2Nb2O7 to 38.6 for [Formula: see text] ([Formula: see text][Formula: see text]MHz). The Curie temperature ([Formula: see text] of the [Formula: see text] sample was 1280[Formula: see text][Formula: see text][Formula: see text]5[Formula: see text]C. The phase transition was confirmed to be the second order.

Removing Substrate Background in TEM Microanalysis

1974 ◽  
Vol 32 ◽  
pp. 568-569
Author(s):  
John C. Russ ◽  
Nicholas C. Barbi
Keyword(s):  
Electrical Conductivity ◽  
Rapid Growth ◽  
Organic Film ◽  
Absolute Concentration ◽  
Background Signal ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

Chemical and Electrochemical Heteroepitaxial Growth of Chalcogenide Semiconductors from Solutions

1996 ◽  
Vol 451 ◽  
Author(s):  
D. Lincot ◽  
M. J. Furlong ◽  
M. Froment ◽  
R. Cortes ◽  
M. C. Bernard
Keyword(s):  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
Basic Principles ◽  
Lattice Match ◽  
X Ray ◽  
Chalcogenide Semiconductors ◽  
Influence Of Temperature On ◽  
Deposition Processes ◽  
A Site ◽  
Site Selective

ABSTRACTChalcogenide semiconductors have been deposited epitaxially from aqueous solutions either chemically or electrochemically at growth rates of up to 0.7 μmhr−1. After recalling the basic principles of these deposition processes, results are presented concerning chemically deposited CdS on InP, GaP and CuInSe2 substrates, electrodeposited CdTe on InP, and CdSAnP heterostructures. Characterisation of these structures by RHEED, TEM, HRTEM, and glazing angle X ray diffraction allows to analyse the effects of substrate orientation, polarity, lattice match plus the influence of temperature on epitaxial growth. These results are discussed in terms of self organisation and a site selective growth mechanisms due to the free enegy of formation of each compound.

scholarly journals Thermoelectric Generator Using Polyaniline-Coated Sb2Se3/β-Cu2Se Flexible Thermoelectric Films

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1518
Author(s):  
Minsu Kim ◽  
Dabin Park ◽  
Jooheon Kim
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Field Emission ◽  
Photoelectron Spectroscopy ◽  
Thermoelectric Generator ◽  
Hydrothermal Reaction ◽  
Water Evaporation ◽  
Pani Film ◽  
Portable Devices ◽  
X Ray

Herein, Sb2Se3 and β-Cu2Se nanowires are synthesized via hydrothermal reaction and water evaporation-induced self-assembly methods, respectively. The successful syntheses and morphologies of the Sb2Se3 and β-Cu2Se nanowires are confirmed via X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), and field emission transmission electron microscopy (FE-TEM). Sb2Se3 materials have low electrical conductivity which limits application to the thermoelectric generator. To improve the electrical conductivity of the Sb2Se3 and β-Cu2Se nanowires, polyaniline (PANI) is coated onto the surface and confirmed via Fourier-transform infrared spectroscopy (FT-IR), FE-TEM, and XPS analysis. After coating PANI, the electrical conductivities of Sb2Se3/β-Cu2Se/PANI composites were increased. The thermoelectric performance of the flexible Sb2Se3/β-Cu2Se/PANI films is then measured, and the 70%-Sb2Se3/30%-β-Cu2Se/PANI film is shown to provide the highest power factor of 181.61 μW/m·K2 at 473 K. In addition, a thermoelectric generator consisting of five legs of the 70%-Sb2Se3/30%-β-Cu2Se/PANI film is constructed and shown to provide an open-circuit voltage of 7.9 mV and an output power of 80.1 nW at ΔT = 30 K. This study demonstrates that the combination of inorganic thermoelectric materials and flexible polymers can generate power in wearable or portable devices.

scholarly journals Paclitaxel loading in cationic liposome vectors is enhanced by replacement of oleoyl with linoleoyl tails with distinct lipid shapes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuhong Zhen ◽  
Kai K. Ewert ◽  
William S. Fisher ◽  
Victoria M. Steffes ◽  
Youli Li ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Membrane Structure ◽  
Cationic Liposome ◽  
Solubility Limit ◽  
Loading Capacity ◽  
Prostate Cancer Cells ◽  
X Ray ◽  
X Ray Scattering ◽  
Cylindrical Micelles ◽  
Molecular Affinity

AbstractLipid carriers of hydrophobic paclitaxel (PTX) are used in clinical trials for cancer chemotherapy. Improving their loading capacity requires enhanced PTX solubilization. We compared the time-dependence of PTX membrane solubility as a function of PTX content in cationic liposomes (CLs) with lipid tails containing one (oleoyl; DOPC/DOTAP) or two (linoleoyl; DLinPC/newly synthesized DLinTAP) cis double bonds by using microscopy to generate kinetic phase diagrams. The DLin lipids displayed significantly increased PTX membrane solubility over DO lipids. Remarkably, 8 mol% PTX in DLinTAP/DLinPC CLs remained soluble for approximately as long as 3 mol% PTX (the solubility limit, which has been the focus of most previous studies and clinical trials) in DOTAP/DOPC CLs. The increase in solubility is likely caused by enhanced molecular affinity between lipid tails and PTX, rather than by the transition in membrane structure from bilayers to inverse cylindrical micelles observed with small-angle X-ray scattering. Importantly, the efficacy of PTX-loaded CLs against prostate cancer cells (their IC50 of PTX cytotoxicity) was unaffected by changing the lipid tails, and toxicity of the CL carrier was negligible. Moreover, efficacy was approximately doubled against melanoma cells for PTX-loaded DLinTAP/DLinPC over DOTAP/DOPC CLs. Our findings demonstrate the potential of chemical modifications of the lipid tails to increase the PTX membrane loading while maintaining (and in some cases even increasing) the efficacy of CLs. The increased PTX solubility will aid the development of liposomal PTX carriers that require significantly less lipid to deliver a given amount of PTX, reducing side effects and costs.

scholarly journals Crystal Structure Refinements of Four Monazite Samples from Different Localities

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1028 ◽  
Author(s):  
M. Mashrur Zaman ◽  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Large Unit Cell ◽  
A Site

This study investigates the crystal chemistry of monazite (APO4, where A = Lanthanides = Ln, as well as Y, Th, U, Ca, and Pb) based on four samples from different localities using single-crystal X-ray diffraction and electron-probe microanalysis. The crystal structure of all four samples are well refined, as indicated by their refinement statistics. Relatively large unit-cell parameters (a = 6.7640(5), b = 6.9850(4), c = 6.4500(3) Å, β = 103.584(2)°, and V = 296.22(3) Å3) are obtained for a detrital monazite-Ce from Cox’s Bazar, Bangladesh. Sm-rich monazite from Gunnison County, Colorado, USA, has smaller unit-cell parameters (a = 6.7010(4), b = 6.9080(4), c = 6.4300(4) Å, β = 103.817(3)°, and V = 289.04(3) Å3). The a, b, and c unit-cell parameters vary linearly with the unit-cell volume, V. The change in the a parameter is large (0.2 Å) and is related to the type of cations occupying the A site. The average <A-O> distances vary linearly with V, whereas the average <P-O> distances are nearly constant because the PO4 group is a rigid tetrahedron.

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

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