scholarly journals Dielectric Properties of (CdSe)1-X(ZnS)X Mixed Semiconductor Compounds

2012 ◽  
Vol 9 (2) ◽  
pp. 179-189 ◽  
Author(s):  
K. YADAIAH ◽  
J. KRISHNAIAH ◽  
VASUDEVA REDDY ◽  
M. NAGABHUSHANAM
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Relaxation Times ◽  
Dielectric Constants ◽  
Semiconductor Materials ◽  
Precipitation Method ◽  
Semiconductor Compounds ◽  
Optical Dielectric ◽  
Co Precipitation

Dielectric permittivity has been an important property of binary and mixed semiconductor materials as it is closely related to the studies on polarization and relaxation mechanisms. Therefore, dielectric properties of (CdSe)1-X(ZnS)X mixed semiconductors are studied at different frequencies. The mixed semiconductor samples used in the study are grown by controlled co-precipitation method. From these studies ac conductivity, static and optical dielectric constants, relaxation times and activation energy of dipole relaxation are determined. The variation of dielectric constant with frequency and composition of the sample was explained on the basis of Koops grain boundary mechanism.

scholarly journals Investigation of AC-Measurements of Epoxy/Ferrite Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 492 ◽  
Author(s):  
Moustafa A. Darwish ◽  
Alex V. Trukhanov ◽  
Oleg S. Senatov ◽  
Alexander T. Morchenko ◽  
Samia A. Saafan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
High Frequency ◽  
Precipitation Method ◽  
Semiconductor Behavior ◽  
Ferrite Composites ◽  
Co Precipitation ◽  
Theoretical Results ◽  
Composite Samples

A pure ferrite and epoxy samples as well as the epoxy/ferrite composites with different 20 wt.%, 30 wt.%, 40 wt.%, and 50 wt.% weight ferrite contents have been prepared by the chemical co-precipitation method. AC-conductivity and dielectric properties such as the dielectric constant and dielectric loss of the prepared samples have been studied. The obtained results showed that the samples had a semiconductor behavior. The dielectric constant of the composites has been calculated theoretically using several models. For the composite sample that contains 20 wt.% of ferrites, these models give satisfactory compliance, while for the composite samples with a higher percentage of nanofillers, more than 30 wt.% theoretical results do not coincide with experimental data. The investigated polymer has very low conductivity, so this type of polymer can be useful for high-frequency applications, which can reduce the losses caused by eddy current. Thus, the prepared samples are promising materials for practical use as elements of microwave devices.

Structural and Dielectric Properties of Zn1-xMoxO Nanoparticles

2020 ◽  
Vol 13 (2) ◽  
pp. 165-170
Keyword(s):  
Zinc Oxide ◽  
Dielectric Properties ◽  
Ac Conductivity ◽  
Hexagonal Wurtzite Structure ◽  
Dielectric Constants ◽  
Precipitation Method ◽  
Dielectric Parameters ◽  
Mo Doping ◽  
Lcr Meter ◽  
Co Precipitation

Abstract: In this work, samples of zinc oxide nanoparticles doped by molybdenum (Zn1-xMoxO with 0 ≤ x ≤ 0.1) were prepared by using the wet co-precipitation method. The characterization of the prepared samples was carried out by means of X-ray powder diffraction (XRD). The samples reserved their hexagonal wurtzite structure with Mo doping and showed a decrease in the crystallite size up to x = 0.04 followed by a further increase. On the other hand, dielectric measurements were performed using an LCR meter. The effect of frequency and temperature on the dielectric properties such as the real and imaginary parts of dielectric constant (ε^' and ε'', respectively), dielectric loss (tanδ) and ac-conductivity (σ_ac) of Mo-doped zinc oxide samples, was studied in the frequency range (100 Hz - 1 MHz) and at temperatures (300 - 773 K). The values of room temperature dielectric parameters were found to be strongly dependent on the Mo-doping. However, the increase in temperature caused an enhancement in the values of the dielectric parameters, particularly at 773 K. Keywords: Zinc oxide, XRD, Dielectric constants, Ac-conductivity.

Structure and Dielectric Properties of (Gd0.4Sm0.5Yb0.1)2(Zr1-xCex)2O7 Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 394-397
Author(s):  
Ling Liu ◽  
Qiang Xu ◽  
Fu Chi Wang
Keyword(s):  
Rare Earth ◽  
Dielectric Properties ◽  
Pyrochlore Structure ◽  
Microwave Frequency ◽  
Phase Region ◽  
Dielectric Constants ◽  
Precipitation Method ◽  
Low Dielectric ◽  
Pyrochlore Type ◽  
Co Precipitation

Complex rare-earth zirconates (Gd0.4Sm0.5Yb0.1)2(Zr1-xCex)2O7 (x=0, 0.3, 0.4) powders were synthesized by co-precipitation method. XRD and SEM results revealed that the complex rare-earth zirconates with single pyrochlore structure were prepared and no other phases existed among the grains. The dielectric properties of these compounds were investigated at low and microwave frequencies. It was found that they have intermediate dielectric constants and low dielectric loss in the whole frequency region, and they show the dielectric permittivity with weak frequency dependence. Substituting Zr4+ by Ce4+ leaded to smaller permittivity. Meanwhile, the dielectric contant values increase with increasing in the r(A3+)/r(B4+) value in the pyrochlore-type phase region, which can be explained by the increase in the degree of ordering of oxygen vacancy. This new series of pyrochlore type oxides would be potential candidates for electronic ceramic applications and microwave frequency components.

Microstructure and Dielectric Properties of BaFe12O19 Hexaferrite Nanoparticles: Effect of Cobalt Addition and Calcination Temperature

2020 ◽  
Vol 13 (3) ◽  
pp. 211-219
Keyword(s):  
Dielectric Properties ◽  
Barium Hexaferrite ◽  
Hexagonal Structure ◽  
Dielectric Constants ◽  
Precipitation Method ◽  
Calcination Temperatures ◽  
Transmission Electron ◽  
Tan Δ ◽  
Co Addition ◽  
Co Precipitation

Abstract: M-type Barium Hexaferrite (BaFe12O19) is a promising compound for technological applications because of its high permeability, high saturation magnetization and excellent dielectric properties. In this study, the microstructure and dielectric properties of CoxBaFe12O19Hexaferrite were investigated. The co-precipitation method was employed to prepare CoxBaFe12O19 nanoparticles, with x = 0, 0.04, 0.06 and 0.1 wt. %, at two different calcination temperatures (900oC and 950oC). The microstructure of the samples was examined through X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The hexagonal structure of the prepared samples was confirmed from XRD results. TEM images reveal the formation of agglomerated nanoparticles with different size distribution. The dielectric properties of the samples were studied through HIOKI 3532-50 LCR-Hi TESTER as a function of frequency (100 kHz–3MHz) and temperature (25 °C–500°C). The effects of Co addition, frequency and temperature on the dielectric constants (ɛʹ and ɛʹʹ), loss tangent (tan δ) and ac conductivity (σac) have been explained on the basis of hopping of electrons between Fe2+ and Fe3+ ions. Keywords: BaFe12O19 Hexaferrite, Co-precipitation method, XRD, Dielectric properties.

Dielectric Properties of CaCu3Ti4O12 Ceramics

2010 ◽  
Vol 434-435 ◽  
pp. 253-255
Author(s):  
Jing Han You ◽  
Xiao Yang Gong ◽  
Tong Wei Li ◽  
Qing Dong Chen ◽  
Li Ben Li
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
High Frequency ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
Debye Relaxation ◽  
Relaxation Theory ◽  
Reaction Method ◽  
Theoretical Results

CaCu3Ti4O12 ceramics were prepared by the traditional solid-state reaction method and the dielectric properties were investigated, the activation energy and relaxation time factor of the samples were calculated. Debye relaxation theory was attempted to analyze the experimental datum, the static and high-frequency dielectric constants were obtained according to Cole-Cole spectra. The temperature dependence of the dielectric constant of CaCu3Ti4O12 were fitted by computer and the theoretical results nearly agree with experimental results.

Dielectric Properties of Y3Fe5O12 (YIG) Prepared at Different Molarities of NaOH

2020 ◽  
Vol 13 (3) ◽  
pp. 221-226
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Yttrium Iron Garnet ◽  
Lattice Parameter ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Yttrium Iron ◽  
X Ray ◽  
Co Precipitation ◽  
Iron Garnet

Abstract: In this study, Yttrium Iron Garnet (Y3Fe5O12) (YIG) powders were synthesized via co-precipitation method, followed by calcining the precipitates at 1100˚C. The garnets produced were obtained from aqueous iron and yttrium chloride mixtures using different molarities of NaOH (M=2, 3, 4 and 5) at pH=12. The phase formation and crystallography were investigated using X-ray diffraction (XRD), the morphology was investigated using transmission electron microscopy (TEM) and the dielectric properties were measured using an impedance analyzer in the frequency range 0.5 - 5MHz, in a temperature range 22 - 350˚C. X-ray diffraction peaks showed the formation of cubic YIG with lattice parameter varying between 12.334 and 12.339 Å. The grain size, measured from TEM images, decreased with the increase of the molarity of NaOH. Plots of the real part of the dielectric constant ε′, the imaginary part of the dielectric constant ε'', loss tangent tan δ and ac conductivity σac as functions of frequency and temperature, respectively, were obtained. It was observed that the highest values of the dielectric constant were obtained in the 2M sample. Keywords: Dielectric properties, Yttrium Iron Garnet (YIG), Co-precipitation method, NaOH molarity.

Magnetic and dielectric properties study of cobalt ferrite nanoparticles synthesized by co-precipitation method

2011 ◽  
Vol 1368 ◽  
Author(s):  
M. Krishna Surendra ◽  
D. Kannan ◽  
M. S. Ramachandra Rao
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Saturation Magnetization ◽  
Cobalt Ferrite ◽  
Ferrite Nanoparticles ◽  
Precipitation Method ◽  
Co Precipitation ◽  
Inert Layer

Abstract:Cobalt ferrite nanoparticles were prepared by co-precipitation method and were heat treated at 100 oC, 200 oC, 400 oC and 600 oC for 2 h to increase the particle size. Phase purity of samples was confirmed by X-ray diffraction. Scherrer formula calculations showed crystallite size varied from 12 to 24 nm when heated from 100 oC to 600 oC. Transmission electron microscopy reveals a uniform and narrow particle size distribution about 12 nm for as-prepared cobalt ferrite particles. Room temperature saturation magnetization was found to vary from 40.8 to 67.0 emu/g as the particle size increased from12 nm to 24 nm. Increase in saturation magnetization with increase in particle size was attributed to the presence of magnetic inert layer on the surface of nanoparticles. Inert layer thickness calculated at 10 K and 300 K was 6 Å and 11 Å respectively. The dielectric properties ε’, tanδ, Z and θ have been studied as a function of frequency and particles size. For the 12 nm grain size, the dielectric constant is one order higher than that of bulk cobalt ferrite. Increase in the grain size showed an increase in the dielectric constant. The increase in the conductivity with grain size is mainly due to the grain size effects. The present study shows that the dielectric properties can be tailor-made to suit the requirement of a particular application by controlling the grain size.

Tuning the mechanical and dielectric properties of zinc incorporated hydroxyapatite

2020 ◽  
Vol 16 ◽  
Author(s):  
Alliya Qamar ◽  
Rehana Zia ◽  
Madeeha Riaz
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bone Growth ◽  
Healing Process ◽  
Secondary Phase ◽  
Chemical Precipitation ◽  
Hexagonal Structure ◽  
Precipitation Method ◽  
Low Frequencies ◽  
A Minor

Background: Hydroxyapatite is similar to bone mineral in chemical composition, has good biocompatibility with host tissue and bone. Objective: This work aims to tailor the mechanical and dielectric properties of hydroxyapatite with zinc sudstitution, to improve wearability of implant and accelerate the healing process. Method: Pure and zinc incorporated hydroxyapatite Ca10(PO4)6(OH)2 samples have been successfully prepared by means of the chemical precipitation method. Results: The results showed that hydroxyapatite(Hap) having hexagonal structure was the major phase identified in all the samples. It was found that secondary phase of β-tricalcium phosphate (β-TCP) formed due to addition of Zinc resulting in biphasic structure BCP (Hap + β-TCP). A minor phase of ZnO also formed for higher concentration of Zn (Zn ≥ 2mol%) doping. It was found that the Zn incorporation to Hap enhanced both mechanical and dielectric properties without altering the bioactive properties. The microhardness increased upto 0.87 GPa for Zn concentration equal to 1.5mol%, which is comparable to the human bone ~0.3 - 0.9 GPa. The dielectric properties evaluated in the study showed that 1.5 mol% Zn doped hydroxyapatite had highest dielectric constant. Higher values of dielectric constant at low frequencies signifies its importance in healing processes and bone growth due to polarization of the material under the influence of electric field. Conclusion: Sample Z1.5 having 1.5 mol% Zn doping showed the most optimized properties suitable for bone regeneration applications.

DIELECTRIC CONSTANT AND SEEBECK COEFFICIENT FOR SEMICONDUCTORS: THERMODYNAMIC AND DFT STUDIES

2013 ◽  
Vol 12 (06) ◽  
pp. 1350057 ◽  
Author(s):  
HSIU-YA TASI ◽  
CHAOYUAN ZHU
Keyword(s):  
Boundary Condition ◽  
Dielectric Constant ◽  
Seebeck Coefficient ◽  
Gas Phase ◽  
Present Method ◽  
Dielectric Constants ◽  
Semiconductor Materials ◽  
Electronic Polarizability ◽  
Seebeck Coefficients ◽  
Good Agreement

Dielectric constants and Seebeck coefficients for semiconductor materials are studied by thermodynamic method plus ab initio quantum density functional theory (DFT). A single molecule which is formed in semiconductor material is treated in gas phase with molecular boundary condition and then electronic polarizability is directly calculated through Mulliken and atomic polar tensor (APT) density charges in the presence of the external electric field. This electronic polarizability can be converted to dielectric constant for solid material through the Clausius–Mossotti formula. Seebeck coefficient is first simulated in gas phase by thermodynamic method and then its value divided by its dielectric constant is regarded as Seebeck coefficient for solid materials. Furthermore, unit cell of semiconductor material is calculated with periodic boundary condition and its solid structure properties such as lattice constant and band gap are obtained. In this way, proper DFT function and basis set are selected to simulate electronic polarizability directly and Seebeck coefficient through chemical potential. Three semiconductor materials Mg 2 Si , β- FeSi 2 and SiGe are extensively tested by DFT method with B3LYP, BLYP and M05 functionals, and dielectric constants simulated by the present method are in good agreement with experimental values. Seebeck coefficients simulated by the present method are in reasonable good agreement with experiments and temperature dependence of Seebeck coefficients basically follows experimental results as well. The present method works much better than the conventional energy band structure theory for Seebeck coefficients of three semiconductors mentioned above. Simulation with periodic boundary condition can be generalized directly to treat with doped semiconductor in near future.

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