X-ray emission spectroscopy with electron excitation covering elements
                    <sub>4</sub>
                    Be-
                    <sub>92</sub>
                    U

Macdonald, G. L.; Harwood, Margaret

doi:10.1088/0508-3443/6/5/305

Cited by 22 publications

(37 citation statements)

References 9 publications

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“…Although a zero value of D1 was used in generating the CSD data of rows A and D, if a non-zero value had been included, as is always necessary for the analysis of experimental data, we w ould have found that the D1 " estimate in lines B and C should have been designated as 1 C1 and C0 from such t results. In the absence of any DSD in the measured frequency range, one can take the actual, always present, D1 equal to D0 , and we m ust identify the apparent DSD and nonzero D as arising solely from CSD.…”

Section: Direct Data Tting a Csd-type Datamentioning

confidence: 99%

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Macdonald¹

1999

Braz. J. Phys.

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Relations and distinctions which are relevant to small-signal electrical-relaxation behavior are reviewed and applied to the important problem of identifying the physical processes leading to dispersed relaxation response. Complex-nonlinear-least-squares tting of a response model to frequency-response data is found not to allow one to distinguish unambiguously in most cases between conductive-system response of Wagner-Voigt type, which m a y b e c haracterized by a distribution of conductive-system relaxation times DCRT , and dielectric-system response of Maxwell type, characterized by a d istribution of dielectric-system relaxation times DDRT . In general, one must include a parallel conductivity element, CP, a s w ell as a high-frequencylimiting dielectric-system dielectric constant, in a conductive-system tting model used to represent dielectric-system data with non-zero dc conductivity. Contrary to earlier predictions of Gross and Meixner, accurate numerical inversion of a set of exact frequency-response data to estimate the distribution with which it is associated shows that no discrete line necessarily appears in a DCRT associated with a truncated continuous DDRT. A discrete line can appear in general, however, when CP 6 = 0 and is unaccounted for in an inversion process. The novel result is established that a data set mathematically described in terms of a dielectric system with dc leakage and involving a Maxwell-circuit exponential distribution of relaxation times may b e w ell represented within usual experimental error by a W agner-Voigt conductive system involving a form of the important Kohlrausch-Williams-Watts response model.

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Section: Direct Data Tting a Csd-type Datamentioning

confidence: 99%

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Macdonald¹

1999

Braz. J. Phys.

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“…It should not be confused with the symbol for ohm (fl). One can isolate the dispersive part of the response by defining the normalized immittance [ 18 ] …”

Section: Z'(to)-z'(~ ) + (2/n) T [Xz"(x)-ojz"(o~)] DX ×mentioning

confidence: 99%

“…But note that conducting-system dispersion and dielectric dispersion may occur simultaneously in the same general frequency region [ 19 ]. In this work, we shall consider in detail a derivative method of approximating imaginary-part response from the associated real-part data without extrapolation; a distribution-of-relaxation-times (DRT) alternative to the KKR which avoids many of their limitations; and the estimation of DRT's, or, equivalently, distributions of transition rates or activation energies (DAE's) [ 18 ], directly from IS frequencyresponse data. All KKR calculations herein were carried out with the EQUIVALENT CIRCUIT program [ 3,17 ] and all DRT calculations with the LEVM program [4,5].…”

Section: Z'(to)-z'(~ ) + (2/n) T [Xz"(x)-ojz"(o~)] DX ×mentioning

confidence: 99%

“…(4) to some exact and experimental data to illustrate its strengths and weaknesses. We shall begin by considering a thermally activated conducting system with an exponential distribution of activation energies or transition rates (EDAE) [ 18,19,21 ], a physically-based model which has been found to yield frequency response results in good agreement with both experimental data and some empirical models such as that of Davidson and Cole [22]. For a thermally activated system, we may write…”

Section: An Approximate Transform Using Differentiation: Exact and Exmentioning

confidence: 99%

“…We assume, as usual [18,23], that given a random exponential distribution of barrier heights, the minimum 8 is 0 and the maximum is 8n (<do); thus zw-z.exp (~H), and we shall here take Zo = zm so ~=~N.…”

Section: An Approximate Transform Using Differentiation: Exact and Exmentioning

confidence: 99%

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Alternatives to Kronig-Kramers transformation and testing, and estimation of distributions

Boukamp

Macdonald

1994

Solid State Ionics

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Two alternatives to Kronig-Kramers analysis of small-signal ac immittance data are discussed and illustrated using both synthetic and experimental data. The first, a derivative method of approximating imaginary-part response from real-part data, is found to be too approximate in regions where the imaginary-part varies appreciably with frequency. The second, a distribution of relaxation-times fitting method, is shown to be valuable for testing whether a data set satisfies the Kronig-Kramers relations and so is associated with a system whose properties are time-invariant. It also is valuable for estimating real-or imaginary-part response from the other part, usually with small error. Unlike Kronig-Kramers analysis, the second method usually requires no extrapolation outside the range of the measured data. Finally, this discrete-function method also allows one to estimate the distribution of relaxation times or activation energies associated with a given set of frequency-response data. This application is described and illustrated for both synthetic and experimental data and is shown to yield good but somewhat approximate results for the estimation of continuous distributions. It is particularly valuable for identifying response regions arising from a continuous distribution and distinguishing them from those associated with discrete time-constant response.

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Beneficial Effects of La_0.5Sr_0.5CoO₃ Coatings on Thin‐Film LiMn₂O₄ Cathodes for Lithium Ion Batteries

Scipioni

et al. 2023

Advanced Sustainable Systems

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The severe capacity loss of spinel LiMn2O4 (LMO) limits the utility of this otherwise promising lithium ion battery cathode material. One of the strategies to mitigate capacity fade is applying a coating on LMO particle surfaces. While this approach yields promising results, there is limited understanding of mechanisms whereby coatings improve LMO capacity retention. Herein, the effects of a new protective coating material, La0.5Sr0.5CoO3 (LSCO), in a thin‐film battery geometry that is amenable to fundamental studies of electrode processes, are reported. RF sputtering deposition is used to produce high quality 25–100 nm LMO cathodes on Al2O3 substrates with an intervening Pt/Ti back‐side contact layer. Cycling of the un‐coated cathodes results in capacity loss of 18% over 300 cycles. Adding a 2 nm LSCO layer reduces the capacity loss to 3%. While this may be due in part to reduced Mn dissolution, scanning transmission electron microscopy results indicate that the coating helps to preserve crystallinity and reduce lattice structure distortion due to inhibited formation of defect tetragonal spinel. Three‐electrode electrochemical impedance spectroscopy results reveal that the LSCO coating increases charge transfer and ohmic resistances, but the increases are generally too small to significantly impact cell performance even at high C‐rates.

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X-ray emission spectroscopy with electron excitation covering elements ₄ Be- ₉₂ U

Cited by 22 publications

References 9 publications

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Alternatives to Kronig-Kramers transformation and testing, and estimation of distributions

Beneficial Effects of La_0.5Sr_0.5CoO₃ Coatings on Thin‐Film LiMn₂O₄ Cathodes for Lithium Ion Batteries

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X-ray emission spectroscopy with electron excitation covering elements 4 Be- 92 U

Cited by 22 publications

References 9 publications

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Dispersed electrical-relaxation response: discrimination between conductive and dielectric relaxation processes

Alternatives to Kronig-Kramers transformation and testing, and estimation of distributions

Beneficial Effects of La0.5Sr0.5CoO3 Coatings on Thin‐Film LiMn2O4 Cathodes for Lithium Ion Batteries

Contact Info

Product

Resources

About

X-ray emission spectroscopy with electron excitation covering elements ₄ Be- ₉₂ U

Beneficial Effects of La_0.5Sr_0.5CoO₃ Coatings on Thin‐Film LiMn₂O₄ Cathodes for Lithium Ion Batteries