Schottky Energy Calculations for the Alkali Halides; Details and Results of Successive Approximations

1973 ◽  
Vol 51 (18) ◽  
pp. 1923-1934 ◽  
Author(s):  
I. M. Boswarva ◽  
J. H. Simpson
Keyword(s):  
Dielectric Properties ◽  
Short Range ◽  
Negative Ions ◽  
Alkali Halides ◽  
Successive Approximations ◽  
Point Dipole ◽  
Dielectric Parameters ◽  
Continuum Region ◽  
Region I ◽  
Experimental Values

Results of theoretical determinations of the energy to form a Schottky defect, using a point-dipole model, are presented for alkali halides of the NaCl structure. The calculations were made under the following conditions: (1) Region I (in which the electrostatic and short-range interactions for each ion are treated in detail) contained 6, 18, 26, and 32 ions respectively. (2) Short-range parameters were determined from both the elastic and dielectric properties and the results compared. The "dielectric" parameters produced a better match between the dielectric properties of regions I and II (the dielectric continuum region) and showed better agreement with experimental values for the Schottky energy. (3) Derivations of detailed expressions and calculations were performed independently in two laboratories and cross-checked to eliminate errors.Region I displacements which are presented for the four cases indicate that an instability occurs in the 32-ion case for crystals in which the ions differ considerably in size. An analysis of this problem suggests that a modification of the Born repulsive energy expression is desirable when interaction between negative ions is appreciable.

The Volumes of Formation of Schottky Defects in Ionic Crystals

1971 ◽  
Vol 26 (1) ◽  
pp. 62-68 ◽  
Author(s):  
I. D. Faux ◽  
A. B. Lidiard
Keyword(s):  
Shell Model ◽  
Alkali Halides ◽  
Molecular Volume ◽  
Point Dipole ◽  
Lattice Statics ◽  
Region I ◽  
Lattice Approximation ◽  
Region Ii ◽  
Formation Energies ◽  
Static Lattice

AbstractIn this paper we calculate the volumes and energies of formation of Schottky defects in the alkali halides NaCl, NaBr, KCl and KBr. Both the polarisable point-dipole and a simple shell model are evaluated. The calculation uses a generalised and extended Mott-Littleton approach in conjunction with results derived previously by the lattice statics method of Kanzaki. The polarisable point-dipole model, as might be expected, is bad, but the shell model leads to good values for the Schottky formation energies, which not only compare well with experiment but are insensitive to the size of the region (‘region I’) around the defect for which the lattice displacements are computed explicitly (i. e. as distinct from the outer Mott-Littleton region, ‘region II’) . The predicted volumes of formation of Schottky defects are less than the molecular volume, νm, i. e. the volumes of relaxation are negative (NaCl, - 0.69 vm; NaBr, - 0.73 vm; KCl, - 0.52 vm; KBr, -0,51 vm in the static lattice approximation). This is in conflict with the results of experiments on the effect of pressure upon the ionic conductivity of these crystals although some other experimental data are consistent with negative relaxation volumes. The disagreement is briefly discussed and the possibility that temperature effects are greater than is implied by the quasi-harmonic model is noted as a possible explanation

Influence of Ca-Doping on Structural, Magnetic and Dielectric Properties of Ba3Co2-xCaxFe24O41 Hexaferrite Powders

2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Sol Gel ◽  
Calcium Content ◽  
Combustion Method ◽  
Dielectric Behavior ◽  
Dielectric Parameters ◽  
Ca Doping ◽  
Auto Combustion ◽  
Magnetic And Dielectric Properties

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper

Short-range forces and the dielectric properties of solid argon

1965 ◽  
Vol 12 (116) ◽  
pp. 393-408 ◽  
Author(s):  
S. Doniach ◽  
R. Huggins
Keyword(s):  
Dielectric Properties ◽  
Short Range ◽  
Solid Argon

scholarly journals Dielectric properties of Li doped Ni-Zn ferrite

2018 ◽  
Vol 16 (36) ◽  
pp. 140-152 ◽  
Author(s):  
Nasma A. Jaber
Keyword(s):  
Sol Gel ◽  
Dissipation Factor ◽  
X Ray Diffraction ◽  
Lithium Ions ◽  
Sem Images ◽  
Dielectric Parameters ◽  
Ferrite Material ◽  
Zn Ferrite ◽  
Auto Combustion ◽  
Experimental Values

Lithium doped Nickel-Zinc ferrite material with chemical formula Ni0.9−2x Zn0.1LixFe2+xO4, where x is the ratio of lithium ions Li+ (x = 0, 0.01, 0.02, 0.03 and 0.04) prepared by using sol-gel auto combustion technique. X-ray diffraction results showed that the material have pure cubic spinal structure with space group Fd-3m. The experimental values of the lattice constant (aexp) were decreased from 8.39 to 8.35 nm with doped Li ions. It was found that the decreasing of the crystallite size with addition of lithium ions concentration. The radius of tetrahedral (rtet) and octahedral (roct) site were computed from cation distribution. SEM images have been taken to show the morphology of compound. The dielectric parameters [dissipation factor (Df), the dielectric constant (Ԑ') and a.c. conductivity (ζac)] of spinal ferrite nano-powder have been measured. The dielectric parameters as a function of concentration have been studied for ferrite synthesis. The saturation of magnetization (Ms), remiensis (Mr) and coersivity (Hc) were found from hysteresis loop. The Ms and Hc varied from 36.47 to 66.15 emu/gm and 103 to 133 Oe for ferrite synthesis, respectively.

The effect of the thickness on structural, optical limiting, and dielectric properties of hybrid coatings rhodamine B dye films on an epoxy polymeric substrate for display applications

2021 ◽  
Author(s):  
Wissal Jilani ◽  
Abdelfatteh Bouzidi ◽  
Albandary Almahri ◽  
Hajer Guermazi ◽  
Ibrahim Yahia
Keyword(s):  
Dielectric Properties ◽  
Rhodamine B ◽  
Laser Power ◽  
Thickness Effect ◽  
Hybrid Coatings ◽  
Laser Dye ◽  
Polymeric Substrate ◽  
Coating Films ◽  
Dielectric Parameters ◽  
Intensity Effect

Abstract Various thickness of Rhodamine B (RhB) laser dye was deposited on epoxy polymeric as a new dielectric organic substrate by spin coating method for the first time. This study focused on the newly considered RhB dye on an epoxy substrate for wide-scale applications. The thickness effect on structural, optical, and dielectric properties of the hybrid coating films was performed. The XRD patterns of the films indicated a large hump amorphous design and lack of Bragg peak intensity associated with the RhB laser dye, due to amorphous film concentration. From UV-Visible spectroscopy, the optical absorption edge shifts to the higher wavelengths direction (redshift) with the variation in RhB dye thicknesses. It was found that the energy band gap decreased when the RhB dye film thickness changed. The refractive index is an important parameter influencing the optical component design. Their values vary according to each relationship that extremely useful the films in optical devices. Laser power attenuation sensitivity of pure epoxy polymeric substrate and its coating films shows that under reducing the thicknesses of RhB dye, the laser power intensity effect increases. Several dielectric parameters are extracted from the series and parallel capacitance measurements. The present results offer new material films for luminescent energy solar concentrator applications.

Dielectric Properties of Polymers Filled with Dispersed Metals

2002 ◽  
Vol 10 (3) ◽  
pp. 219-228 ◽  
Author(s):  
Ye.P. Mamunya ◽  
V.V. Davydenko ◽  
H. Zois ◽  
L. Apekis ◽  
A.A. Snarskii ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Particle Distribution ◽  
Volume Fraction ◽  
Filler Concentration ◽  
Threshold Region ◽  
Particle Sizes ◽  
Dielectric Parameters ◽  
Dielectric Characteristics ◽  
Thermoset Resins ◽  
Filler Distribution

The authors have studied the dielectric properties of composite materials based on both thermoplastic and thermoset resins filled with nickel or copper, with various particle sizes and shapes. In addition, two types of particle distribution, random and segregated, were produced for composites filled with nickel. The main objective was to study the effect of the above factors on the dielectric properties of the composites. The concentration dependence of the dielectric parameters (i.e. the real, ∊′, and the imaginary, ∊″, parts of the complex dielectric permittivity and the dielectric loss tangent, tanδ), calculated for all the systems studied, demonstrates a critical behaviour in the percolation threshold region, with maximum values reached at a volume fraction ϕ = ϕc. The dependence of the dielectric parameters on concentration follows power-law behaviour in the ϕ < ϕc region. The critical exponent value for ∊′ is q = 0.75, in agreement with the theoretical one. The dielectric characteristics of the filled composites are more sensitive to the spatial filler distribution. For the segregated PVC-Ni system with an ordered filler distribution, the value of ϕc is much lower than for ER-Ni composites with a random filler distribution. Besides, for the segregated PVC-Ni system, the value of q is not constant, as it depends on the filler concentration. A model for the structure, which explains this behaviour, is proposed.

NEUTRON DIFFUSE SCATTERING IN LEAD-BASED RELAXOR FERROELECTRICS AND ITS RELATIONSHIP TO THE ULTRA-HIGH PIEZOELECTRICITY

2012 ◽  
Vol 02 (02) ◽  
pp. 1241005 ◽  
Author(s):  
PETER M. GEHRING
Keyword(s):  
Dielectric Properties ◽  
Single Crystal ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Diffuse Scattering ◽  
Short Range ◽  
Piezoelectric Coefficient ◽  
Relaxor Ferroelectrics ◽  
Scattering Measurements

A brief review is presented that summarizes recent neutron diffuse scattering measurements on single crystal PbMg1/3Nb2/3O3 (PMN) and PbZn1/3Nb2/3O3 (PZN) doped with PbTiO3 (PT). Emphasis is placed on results that suggest that the short-range, polar correlations observed in these systems are connected to the anomalous relaxor dielectric properties, and in particular to the large values of the piezoelectric coefficient d33 near the morphotropic phase boundary.

Effect of Fungicide Treatment on Dielectric Properties of a Vegetable Seed

2015 ◽  
Vol 5 (2) ◽  
Author(s):  
Vishal Singh Chandel ◽  
Atiq UR Rahmanm ◽  
J. P. Shukla ◽  
Rajiv Manohar ◽  
Mohd. Shafi Khan
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Considerable Change ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Hewlett Packard ◽  
Fungicide Treatment ◽  
Vegetable Seed

Effect of fungicides' (thiram, captan, carbendazim, bagalol) treatment on dielectric constant and dielectric loss of a vegetable seed, namely the brinjal at given moisture content and bulk density was examined using Hewlett-Packard (HP-4194A) impedance/gain phase analyzer over the frequency range of 0.01 to 10 MHz and temperature range of 30-450C. Julabo (temperature controller, F-25, Germany) was used for keeping the temperature of seeds constant. Study showed that fungicide treatment cast considerable change in dielectric parameters namely the dielectric constant and dielectric loss.

Sign in / Sign up

Export Citation Format

Share Document