Electrical and mechanical relaxation in CaF2 doped with NaF

Johnson, Howard B.; Tolar, Neal J.; Miller, Gerald R.; Cutler, Ivan B.

doi:10.1016/0022-3697(69)90336-9

Cited by 33 publications

(7 citation statements)

References 11 publications

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“…It should be pointed out here that only a few system shows ideal (Debye) behaviour. Johnson et al [10] reported that the distribution of relaxations was attributed to dipole-dipole interactions followed by the following Gaussian distribution [8]:…”

Section: Resultsmentioning

confidence: 99%

Electrical Measurements on Musa Acuminata Colla

Omprakash¹,

Prasad²,

Prasad³

et al. 2014

ujeee

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Typical Electrical feature of Musa acuminata colla (common name of commercially available banana) peel was identified as inhomogeneous lossy-dielectric. Considering in this direction, detailed impedance analysis was made at room temperature in the frequency range of 0.001 Hz to 1 M Hz. Impedance relaxation was well-fitted into Gaussian curves. The complex impedance plot, associated with two depressed semicircles, indicates Warburg-diffusion phenomenon. Randles's plot and frequency vs. admittance plot confirm the same. The results were corroborated by Jonscher's Universal law for better understanding of the inhibitor (corrosion-free) nature of the banana-peel.

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Section: Resultsmentioning

confidence: 99%

Electrical Measurements on Musa Acuminata Colla

Omprakash¹,

Prasad²,

Prasad³

et al. 2014

ujeee

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“…From the linear fit, v 0 = 1.51 Â 10 11 Hz, and the activation energy E a is 0.45 eV, which is larger than typical values observed in Nbbased pyrochlores, for example 0.32 eV in Ca-Ti-Nb-O pyrochlore and 0.14 eV in Bi-Zn-Nb-O pyrochlore (Roth et al, 2008;Nino, 2002 Structural comparison of three weberite-type structures (Allpress & Rossell, 1979;Rossell, 1979). (Johnson et al, 1969;Cheng et al, 2004). Thus, the calculated E a is acceptable.…”

Section: Dielectric Propertiesmentioning

confidence: 92%

Complex ceramic structures. I. Weberites

Cai

Nino

2009

Acta Crystallogr B Struct Sci

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The weberite structure (A2B2X7) is an anion-deficient fluorite-related superstructure. Compared with fluorites, the reduction in the number of anions leads to a decrease in the coordination number of the B cations (VI coordination) with respect to the A cations (VIII coordination), thus allowing the accommodation of diverse cations. As a result, weberite compounds have a broad range of chemical and physical properties and great technological potential. This article summarizes the structural features of weberite and describes the structure in several different ways. This is the first time that the stacking vector and stacking angle are used to represent the weberite structure. This paper also discusses the crystallographic relationship between weberite, fluorite and pyrochlore (another fluorite-related structure). The cation sublattices of weberite and pyrochlore are correlated by an axial transformation. It has been shown that the different coordination environment of anions is due to the alternating layering of the AB3 and A3B close-packed cation layers. A stability field of weberite oxides is proposed in terms of the ratio of ionic radius of cations and relative bond ionicity. In addition, a selection of weberite compounds with interesting properties is discussed.

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“…~a z~a ; complexes have tetragonal symmetry and would therefore couple with astressalong < 100 > or < 110 >,butnot < 111 >, whereas Na; Fv-complexes have trigonal symmetry and therefore couple with a stress along < 111 > or < 110 >, but not < 100 >. As pointed out by Lidiard [27] the absence of a o < 100 > relaxation in the anelastic measurements of Johnson et al [28] is clear evidence for charge compensation of the substitutional Naf ions by F-vacancies. In addition the formation of intrinsic Frenkel defects on the anion sublattice must be considered.…”

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confidence: 97%

Point Defect Parameters for Calcium Fluoride From Ionic Conductivity Measurements at Low Temperatures

Jacobs

Ong

1976

J. Phys. Colloques

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Rbsum6. -La conductivite des cristaux, purs et dopes au sodium, a kt6 mesurke B des temperatures allant jusqu'a 1 125 K, en evitant toute reaction chimique entre le fluorure de calcium et la vapeur d'eau residuelle, ou l'oxygkne. Les donnees ont kt6 analysks a l'aide de techniques des moindres carres non lineaires pour obtenir des valeurs numeriques des paramktres gouvernant la formation et la migration des dkfauts. Ces resultats sont comparQ avec des travaux experimentaux et theoriques anttrieurs, et montrent que la valeur probable de l'bnergie de formation des defauts de Frenkel dans le sous-reseau d'anions est 2,7 eV et que les energies de migration des lacunes et des interstitiels anioniques se situent respectivement dans les intervalles 0,35-0,55 eV et 0,78-0,92 eV.Abstract. -The ionic conductivity of pure and sodium doped calcium fluoride crystals has been measured at temperatures up to 1 125 K, avoiding chemical reaction of the calcium fluoride with residual water vapour or oxygen. The data have been analyzed using non-linear least squares techniques to yield numerical values of the parameters governing the formation and migration of defects. These results are compared with previous experimental and theoretical work and show that the probable value of the formation energy of Frenkel defects on the anion sub-lattice is 2.7 eV and that the migration energies of anion vacancies and interstitials lie in the ranges 0.35-0.55 eV and 0.78-0.92 eV, respectively.

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Electrical and mechanical relaxation in CaF2 doped with NaF

Cited by 33 publications

References 11 publications

Electrical Measurements on Musa Acuminata Colla

Electrical Measurements on Musa Acuminata Colla

Complex ceramic structures. I. Weberites

Point Defect Parameters for Calcium Fluoride From Ionic Conductivity Measurements at Low Temperatures

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