Ionic Conductivity of Potassium Bromide Crystals

1971 ◽  
Vol 49 (16) ◽  
pp. 2098-2105 ◽  
Author(s):  
Suresh Chandra ◽  
John Rolfe
Keyword(s):  
Defect Formation ◽  
Formation Enthalpy ◽  
Potassium Bromide ◽  
Negative Ion ◽  
Coulomb Interactions ◽  
Transport Parameters ◽  
Vacancy Migration ◽  
Charged Defects ◽  
Positive Ion ◽  
Migration Enthalpy

The electrical conductivity of single crystals of potassium bromide was measured as a function of temperature, and as a function of the concentration of calcium bromide or potassium carbonate impurity. The results were analyzed on the assumption that the observed conductivity was due entirely to the motion of separated anion and cation vacancies (Schottky defects), with Coulomb interactions between charged defects. Agreement between measured and calculated conductivities at all temperatures showed that this assumption was reasonable. The values obtained for transport parameters were: Schottky-defect formation enthalpy hs = 2.53 eV, entropy Ss = 10.3k; positive ion vacancy migration enthalpy Δh1 = 0.65 eV, entropy Δs1 = 1.89k; negative ion vacancy migration enthalpy Δh2 = 1.22 eV, entropy Δs2 = 7.30k; association of calcium ions and positive ion vacancies enthalpy x = 0.61 eV, entropy η = 2.23k, where k is Boltzmann's constant.

Ionic Conductivity of Rubidium Iodide Crystals

1973 ◽  
Vol 51 (3) ◽  
pp. 236-240 ◽  
Author(s):  
Suresh Chandra ◽  
John Rolfe
Keyword(s):  
Ionic Conductivity ◽  
Defect Formation ◽  
Formation Enthalpy ◽  
Negative Ion ◽  
Conductivity Measurements ◽  
Transport Parameters ◽  
Vacancy Migration ◽  
Strontium Ions ◽  
Positive Ion ◽  
Migration Enthalpy

The ionic conductivity of pure and strontium-doped rubidium iodide crystals was measured as a function of temperature. Eight transport parameters were calculated from the conductivity results by a nonlinear regression computation. The values obtained for the transport parameters were: Schottky defect formation enthalpy hs = 2.1 eV, entropy ss = 0.5 × 10−3 eV/deg; positive-ion vacancy migration enthalpy Δh1 = 0.60 eV, entropy Δs1 = 0.14 × 10−3 eV/deg; negative-ion vacancy migration enthalpy Δh2 = 1.6 eV, entropy Δs2 = 0.13 × 10−3 eV/deg; association enthalpy of strontium ions and positive-ion vacancies χ = 0.58 eV, entropy η = 0.22 × 10−3 eV/deg. Rubidium carbonate was found to have a negligible solid solubility in rubidium iodide, so that conductivity measurements could not be made on anion-doped crystals. The negative-ion vacancy migration parameters are thus not as accurately determined as the other transport parameters.

Ionic conductivity of potassium iodide crystals

1970 ◽  
Vol 48 (4) ◽  
pp. 397-411 ◽  
Author(s):  
Suresh Chandra ◽  
John Rolfe
Keyword(s):  
Coulomb Interaction ◽  
Defect Formation ◽  
Formation Enthalpy ◽  
Negative Ion ◽  
Appreciable Effect ◽  
Transport Parameters ◽  
Intrinsic Conductivity ◽  
Vacancy Migration ◽  
Positive Ion ◽  
Migration Enthalpy

The electrical conductivity of pure KI, KI + SrI2, and KI + K2CO3 single crystals was measured as a function of temperature. A method for calculating ionic transport parameters from these results was developed, assuming that the conductivity was due entirely to the motion of positive and negative ion vacancies, and including the effect of association and Coulomb interaction between oppositely charged defects. It was shown that the Coulomb interaction had an appreciable effect on the high-temperature intrinsic conductivity, and the extrinsic conductivity of heavily doped crystals. Calculation of transport parameters from intrinsic-conductivity measurements alone gave erroneous results. From the agreement (within experimental error) between the experimental and calculated results, it was concluded that the only defects taking part in the conduction process were Schottky defects. The following parameters were calculated: Schottky-defect formation enthalpy hs = 2.21 eV, entropy ss = 0.765 × 10−3 eV/deg; positive ion vacancy migration enthalpy Δh1 = 0.63 eV, entropy Δs1 = 0.136 × 10−3 eV/deg; negative ion vacancy migration enthalpy Δh2 = 1.29 eV, entropy Δs2 = 0.805 × 10−3 eV/deg; association of divalent cations and positive ion vacancies enthalpy χ = 0.54 eV, entropy η = 0.190 × 10−3 eV/deg.

Ionic conductivity of potassium chloride crystals

1970 ◽  
Vol 48 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Suresh Chandra ◽  
John Rolfe
Keyword(s):  
Potassium Chloride ◽  
Defect Formation ◽  
Divalent Cations ◽  
Formation Enthalpy ◽  
Negative Ion ◽  
Strontium Chloride ◽  
Coulomb Interactions ◽  
Vacancy Migration ◽  
Positive Ion ◽  
Migration Enthalpy

The electrical conductivity of single crystals of potassium chloride was measured as a function of temperature, and as a function of the amount of strontium chloride or potassium carbonate impurity. The results were analyzed by using a least-squares curve-fitting computer program in which the basic assumption was that conductivity was due entirely to the motion of separated anion and cation vacancies (Schottky defects). Coulomb interactions between charged defects were allowed for by using Debye–Hückel theory. With the exception of the conductivity of pure crystals very near the melting point, experimental conductivity measurements agreed with values calculated from the following parameters: Schottky-defect formation enthalpy hs = 2.59 eV, entropy ss = 9.61k; positive ion vacancy migration enthalpy Δh1 = 0.73 eV, entropy Δs1 = 2.70k; negative ion vacancy migration enthalpy Δh2 = 0.99 eV, entropy Δs2 = 4.14k; association of divalent cations and positive ion vacancies enthalpy χ = 0.58 eV, entropy η = 1.30k.

IONIC CONDUCTIVITY OF POTASSIUM BROMIDE CRYSTALS

1964 ◽  
Vol 42 (11) ◽  
pp. 2195-2216 ◽  
Author(s):  
J. Rolfe
Keyword(s):  
Ionic Conductivity ◽  
Single Crystals ◽  
High Temperatures ◽  
Potassium Carbonate ◽  
Calcium Ions ◽  
Transport Number ◽  
Potassium Bromide ◽  
Negative Ion ◽  
Conductivity Measurements ◽  
Positive Ion

The conductivity of single crystals of potassium bromide has been measured as a function of temperature. Potassium carbonate was found to be sufficiently soluble at high temperatures in KBr to cause a conductivity due to negative ion vacancies. The ionic conductivity parameters of KBr were calculated from conductivity measurements on crystals containing known concentrations of potassium carbonate and calcium bromide without recourse to transport number experiments. A simple theory of association was found to be adequate to describe the interaction between calcium ions and positive ion vacancies. The solubility of free divalent impurities in KBr was also calculated from conductivity measurements. The following enthalpy values were found: for formation of a pair of Schottky vacancies, 2.53 eV; for the motion of positive ion vacancies, 0.665 eV; for the motion of negative ion vacancies, 0.87 eV; for the association of calcium ions and positive ion vacancies, 0.46 eV.

Hg1-xCdxTe: Defect Structure Overview

1990 ◽  
Vol 216 ◽  
Author(s):  
M.A. Berding ◽  
A. Sher ◽  
A.-B. Chen
Keyword(s):  
Point Defects ◽  
Defect Structure ◽  
Defect Formation ◽  
Activation Energies ◽  
Mass Action ◽  
Native Defect ◽  
Native Point Defects ◽  
Vacancy Migration ◽  
Formation Energies ◽  
Diffusion Activation

ABSTRACTNative point defects play an important role in HgCdTe. Here we discuss some of the relevant mass action equations, and use recently calculated defect formation energies to discuss relative defect concentrations. In agreement with experiment, the Hg vacancy is found to be the dominant native defect to accommodate excess tellurium. Preliminary estimates find the Hg antisite and the Hg interstitial to be of comparable densities. Our calculated defect formation energies are also consistent with measured diffusion activation energies, assuming the interstitial and vacancy migration energies are small.

Note on radiationless transitions involving three-body collisions

1936 ◽  
Vol 32 (3) ◽  
pp. 482-485 ◽  
Author(s):  
R. A. Smith
Keyword(s):  
Continuous Spectrum ◽  
Negative Ions ◽  
Bound State ◽  
Excess Energy ◽  
Negative Ion ◽  
Positive Ions ◽  
Continuous State ◽  
Direct Formation ◽  
Three Body ◽  
Positive Ion

When an electron makes a transition from a continuous state to a bound state, for example in the case of neutralization of a positive ion or formation of a negative ion, its excess energy must be disposed of in some way. It is usually given off as radiation. In the case of neutralization of positive ions the radiation forms the well-known continuous spectrum. No such spectrum due to the direct formation of negative ions has, however, been observed. This process has been fully discussed in a recent paper by Massey and Smith. It is shown that in this case the spectrum would be difficult to observe.

Serum Lipids Profiling Perturbances in Patients with Ischemic Heart Disease and Ischemic Cardiomyopathy

2020 ◽  
Author(s):  
Lin Yang ◽  
Liang Wang ◽  
Yangyang Deng ◽  
Lizhe Sun ◽  
Bowen Low ◽  
...  
Keyword(s):  
Heart Disease ◽  
Ischemic Heart Disease ◽  
Ischemic Cardiomyopathy ◽  
Serum Lipids ◽  
Ischemic Heart ◽  
Negative Ion ◽  
Serum Samples ◽  
Cross Sectional ◽  
Negative Ion Mode ◽  
Positive Ion

Abstract Background: Ischemic heart disease (IHD) is a common cardiovascular disorder associated with inadequate blood supply to the myocardium. Chronic coronary ischemia leads to ischemic cardiomyopathy (ICM). Despite their rising prevalence and morbidity, few studies have discussed the lipids alterations in these patients. Methods: In this cross-sectional study, we analyzed serum lipids profile in IHD and ICM patients using a lipidomics approach. Consecutive consenting patients admitted to the hospital for IHD and ICM were enrolled. Serum samples were obtained after overnight fasting. Non-targeted metabolomics was applied to demonstrate lipids metabolic profile in control, IHD and ICM patients. Results: A total of 63 and 62 lipids were detected in negative and positive ion mode respectively. Among them, 16:0 Lyso PI, 18:1 Lyso PI in negative ion mode, and 19:0 Lyso PC, 12:0 SM d18:1/12:0, 15:0 Lyso PC, 17:0 PC, 18:1-18:0 PC in positive ion mode were significantly altered both in IHD and ICM as compared to control. 13:0 Lyso PI, 18:0 Lyso PI, 16:0 PE, 14:0 PC DMPC, 16:0 ceramide, 18:0 ceramide in negative ion mode, and 17:0 PE, 19:0 PC, 14:0 Lyso PC, 20:0 Lyso PC, 18:0 PC DSPC, 18:0-22:6 PC in positive ion mode were significantly altered only in ICM as compared to IHD and control. Conclusion: Using non-targeted lipidomics profiling, we have successfully identified a group of circulating lipids that were significantly altered in IHD and ICM. The lipids metabolic signatures shed light on potential new biomarkers and therapeutics for preventing and treating ICM.

THE ELECTRON SPIN RESONANCE SPECTRA OF THE POSITIVE AND NEGATIVE IONS OF DIPHENYLENE

1960 ◽  
Vol 38 (4) ◽  
pp. 503-507 ◽  
Author(s):  
C. A. McDowell ◽  
J. R. Rowlands
Keyword(s):  
Electron Spin Resonance ◽  
Hyperfine Interaction ◽  
Electron Spin ◽  
Negative Ions ◽  
Negative Ion ◽  
Spin Resonance ◽  
Hyperfine Splittings ◽  
Positive Ion

The electron spin resonance spectra of the positive and negative ions of diphenylene have been measured. It has been found that these spectra consist of five lines showing that the observed hyperfine interaction is caused by four equivalent protons. The over-all extent of the positive ion spectrum is 18 gauss compared with that of 12.9 gauss for the negative ion. The hyperfine splittings observed are 4.0 gauss and 2.75 gauss respectively.

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