A Simple Model for Predicating Dielectric Constant of CaCu3Ti4O12-SrTiO3 Composite Ceramics

2011 ◽  
Vol 689 ◽  
pp. 24-28
Author(s):  
Hong Tao Yu ◽  
Wen Bo Zhang ◽  
Jing Song Liu ◽  
Lin Hong Cao ◽  
Han Xing Liu
Keyword(s):  
Dielectric Constant ◽  
Simple Model ◽  
Complex Impedance ◽  
Impedance Spectra ◽  
Composite Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Complex Impedance Spectra ◽  
Variation Tendency

In this work, we have proposed a simple model to predicte the dielectric constant of CaCu3Ti4O12-SrTiO3composite ceramics. The model has been established based on the analysis of composition and microstructure. Two different compositions in the composite ceramics correspond to two different grain sizes, large for CaCu3Ti4O12, and small for SrTiO3, which has been identified by the x-ray diffraction, the scanning electron microscope and the energy spectrum analysis. All specimens have been assumed to be the barrier layer dielectrics in the model, according to the complex impedance spectra. The dielectric constant of serial, parallel, and logarithmic mixture models has been discussed. Compared with the experimental results, the model shows the similar variation tendency as SrTiO3content increases.

NiO Sensing Electrode for NOx Detection at High Temperature

2013 ◽  
Vol 544 ◽  
pp. 76-80
Author(s):  
Tao Feng ◽  
Jin Feng Xia ◽  
Hong Qiang Nian ◽  
De Xin Huang ◽  
Hai Fang Xu ◽  
...  
Keyword(s):  
Screen Printing ◽  
Complex Impedance ◽  
Yttria Stabilized Zirconia ◽  
Impedance Spectra ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Screen Printing Technique ◽  
Printing Technique ◽  
Complex Impedance Spectra

Mixed-potential-type NO2 sensor based on yttria-stabilized zirconia(YSZ) with NiO sensing electrode was prepared by the screen-printing technique and its physical characteristics were studied by the X-ray diffraction and scanning electron microscope. The response of electromotive force (EMF) and complex impedance of the sensor were tested under different NO2 concentrations and temperatures. The results show that, at the range of 550–750 °C, the EMF values are negative and almost linear to the logarithm of NO2 concentration. But the sensitivity of the sensor and the amplitude of the EMF response to NO2 concentration both obviously decrease with the increase of the work temperature. In addition, the semicircular arcs of the complex impedance spectra shrink regularly with a raise of NO2 concentration at 600 °C.

Humidity Sensing Property of Al-Doped Mesoporous Silica

2012 ◽  
Vol 249-250 ◽  
pp. 992-997 ◽  
Author(s):  
Wang Chang Geng ◽  
Li Bing Duan ◽  
Qiu Yu Zhang
Keyword(s):  
Relative Humidity ◽  
Mesoporous Silica ◽  
Complex Impedance ◽  
Impedance Spectra ◽  
X Ray Diffraction ◽  
Humidity Sensing ◽  
X Ray ◽  
Sensing Mechanism ◽  
Sensing Material ◽  
Complex Impedance Spectra

In order to study the humidity sensing property and sensing mechanism of Al-doped mesoporous silica SBA-15 (Al-SBA-15), Al-SBA-15 was prepared by a simple grind method following a heat-treatment process. Its structure and morphology was characterized by X-ray diffraction (XRD), Infrared (IR), scanning electron microscope (SEM). Humidity sensing response was studied and the results indicated that Al-SBA-15 displayed better sensing property when the frequency was 100 Hz. The impedance of Al-SBA-15 changes three orders of magnitude when relative humidity changes from 11% to 95%. Complex impedance spectra, the corresponding equivalent circuit under different relative humidity are carefully analyzed to explore the humidity sensing mechanism of this material. This material can be used as a promising humidity sensing material.

Effects of In-Situ DC-Bias on the Composition, Microstructures and Dielectric Properties of RF Magnetron Reactive Sputtered (Ba,Sr)TiO3 Films

1999 ◽  
Vol 596 ◽  
Author(s):  
Wen-Hao Chan ◽  
Hui-Ling Shen ◽  
Lih-Hsin Chou ◽  
Jinn-Lung Wang ◽  
Jyi-Ching Tsai
Keyword(s):  
Dielectric Constant ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Alloy Target ◽  
Bst Films ◽  
Dc Bias ◽  
Diffraction Patterns

AbstractThin films of (Ba,Sr)TiO3 (BST) have been prepared by rf magnetron reactive sputtering using single alloy target, and in-situ negative DC-bias. Post annealing was applied to the asdeposited films at 620°C for 2 hours in 1 atm oxygen atmosphere. Thin film microstructures and grain sizes were studied and calculated by means of X-ray diffraction, while the film composition was analyzed by Electron Probe X-ray Microanalyzer (EPMA). The dielectric constant of the films was also studied. As the applied DC-bias increased, the dielectric constant increased from 176 to 912, the x-ray diffraction patterns became more intense and narrower, and the (Ba+Sr)/Ti molar ratio increased from 0.70 to 0.83. In-situ DC-bias was observed to be a feasible fabrication process to increase the grain size and relative permittivity of sputtered BST films.

scholarly journals Transport and Dielectric Properties of Mechanosynthesized La2/3Cu3Ti4O12 Ceramics

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 313
Author(s):  
Mohamad M. Ahmad ◽  
Hicham Mahfoz Kotb ◽  
Celin Joseph ◽  
Shalendra Kumar ◽  
Adil Alshoaibi
Keyword(s):  
Dielectric Constant ◽  
Sintering Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Boundary Conductivity ◽  
X Ray ◽  
Giant Dielectric ◽  
Mechanochemical Milling ◽  
Giant Dielectric Constant ◽  
Lower Temperature

La2/3Cu3Ti4O12 (LCTO) powder has been synthesized by the mechanochemical milling technique. The pelletized powder was conventionally sintered for 10 h at a temperature range of 975–1025 °C, which is a lower temperature process compared to the standard solid-state reaction. X-ray diffraction analysis revealed a cubic phase for the current LCTO ceramics. The grain size of the sintered ceramics was found to increase from 1.5 ± 0.5 to 2.3 ± 0.5 μm with an increase in sintering temperature from 975 to 1025 °C. The impedance results show that the grain conductivity is more than three orders of magnitude larger than the grain boundary conductivity for LCTO ceramics. All the samples showed a giant dielectric constant (1.7 × 103–3.4 × 103) and dielectric loss (0.09–0.17) at 300 K and 10 kHz. The giant dielectric constant of the current samples was attributed to the effect of internal barrier layer capacitances due to their electrically inhomogeneous structure.

Impedance Analysis of Layer Structured NBT–CBT Mixed Ceramics

1998 ◽  
Vol 12 (11) ◽  
pp. 433-441 ◽  
Author(s):  
P. S. Rama Sastry ◽  
T. Bhimasankaram ◽  
G. S. Kumar ◽  
G. Prasad
Keyword(s):  
Comparative Study ◽  
Complex Impedance ◽  
Impedance Analysis ◽  
Equivalent Circuits ◽  
Impedance Spectra ◽  
Ceramic System ◽  
Different Temperatures ◽  
Mixed Ceramics ◽  
Mixed Ceramic ◽  
Complex Impedance Spectra

Complex impedance spectra of ferroelectric mixed ceramic system ( Na 0.5 Bi 0.5)1-x Ca x Bi 4 Ti 4 O 15 with x=0, 0.1, 0.3, 0.5, 0.7 and 1 was studied as a function of frequency and temperature in the range 1 KHz to 10 MHz and 30°C to 620°C respectively. Equivalent circuits involving resistive and capacitive elements at different temperatures, activation energies of relaxations and conduction were evaluated using impedance plots. A comparative study of impedance and conductivity facilities an insight in understanding the electrical nature of these electroceramics.

INVESTIGATIONS ON Sm- AND Nb-SUBSTITUTED PZT CERAMICS

2006 ◽  
Vol 20 (29) ◽  
pp. 1879-1882 ◽  
Author(s):  
CHANDRA PRAKASH ◽  
J. K. JUNEJA
Keyword(s):  
Dielectric Constant ◽  
Single Phase ◽  
Xrd Analysis ◽  
Chemical Formula ◽  
X Ray Diffraction ◽  
Pzt Ceramics ◽  
Ceramic Method ◽  
X Ray ◽  
Niobium Doping ◽  
Constant Versus

In the present paper, we report the effect of Samarium substitution and Niobium doping on the properties of a PZT(52:48). The properties studied are: structural, dielectric and ferroelectric. The samples with chemical formula Pb 0.99 Sm 0.01 Zr 0.52 Ti 0.48 O 3 were prepared by solid-state dry ceramic method. Small amount (0.5 wt%) of Nb 2 O 5 was also added. X-ray diffraction (XRD) analysis showed formation of a single phase with tetragonal structure. Dielectric properties were studied as a function of temperature and frequency. Transition temperature, Tc, was determined from dielectric constant versus temperature plot. The material shows well-defined ferroelectric (PE) hysteresis loop.

Complex Impedance Spectroscopy of Bi-Substituted Yttrium Iron Garnet (YIG)

2007 ◽  
Vol 336-338 ◽  
pp. 709-711 ◽  
Author(s):  
Hong Jie Zhao ◽  
Ji Zhou ◽  
Zhi Lun Gui ◽  
Long Tu Li
Keyword(s):  
Grain Boundaries ◽  
Yttrium Iron Garnet ◽  
Complex Impedance ◽  
Physical Structure ◽  
Impedance Spectra ◽  
Yttrium Iron ◽  
Electrical Equivalent Circuit ◽  
Small Resistance ◽  
Iron Garnet ◽  
Complex Impedance Spectra

The effects of Bi-substitution on the complex impedance spectra of yttrium iron garnet (YIG) were studied in this paper. The polycrystalline yttrium iron garnet Y2BiFe5O12 (YIG: Bi) and Y3Fe5O12 (YIG) samples were prepared by solid-reaction method. The complex impedance spectra were measured in the frequency range from 1 KHz to 100MHz at several temperatures between 210oC and 500oC. The complex impedance sample shows that the YIG: Bi can be represented by double Cole-Cole semicircles, and the YIG can be represented by a single Cole semicircle. The physical structure of the specimen was visualized as comprising of small resistance grains separated by large resistance grain boundaries in accordance with the impedance spectra observations. The electrical processes in the sample were modeled in the form of an electrical equivalent circuit made up of a series combination of two parallel RC circuits attributed to grains and grain boundaries. The temperature dependence of bulk resistance indicated an evidence of Arrhenius-type thermally activated process, showing a close to linear variation up to a temperature of 740 K.

Ionic conductivity in nanocrystalline Gd doped ceria

2008 ◽  
Vol 1122 ◽  
Author(s):  
Gianguido Baldinozzi ◽  
David Simeone ◽  
Dominique Gosset ◽  
Mickael Dollé ◽  
Georgette Petot-Ervas
Keyword(s):  
Grain Size ◽  
Ionic Conductivity ◽  
Sol Gel ◽  
Doped Ceria ◽  
Narrow Size Distribution ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
The Impact

AbstractWe have synthesized Gd-doped ceria polycrystalline samples (5, 10, 15 %mol), having relative densities exceeding 95% and grain sizes between 30 and 160 nm after axial hot pressing (750 °C, 250 MPa). The samples were prepared by sintering nanopowders obtained by sol-gel chemistry methods having a very narrow size distribution centered at about 16 nm. SEM and X-ray diffraction were performed to characterize the sample microstructures and to assess their structures. We report ionic conductivity measurements using impedance spectroscopy. It is important to investigate the properties of these systems with sub-micrometric grains and as a function of their composition. Therefore, samples having micrometric and nanometric grain sizes (and different Gd content) were studied. Evidence of Gd segregation near the grain boundaries is given and the impact on the ionic conductivity, as a function of the grain size and Gd composition, is discussed and compared to microcrystalline samples.

Elaboration, Structure and Mössbauer Spectroscopy of Nanostructured Fe100−xSix Powders Elaborated by Mechanical Alloying

SPIN ◽  
2017 ◽  
Vol 07 (02) ◽  
pp. 1750002 ◽  
Author(s):  
M. Hemmous ◽  
A. Guittoum
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Mechanical Alloying ◽  
Hyperfine Magnetic Field ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
The Mean ◽  
Xrd Studies

We have studied the effect of the silicon concentration on the structural and hyperfine properties of nanostructured Fe[Formula: see text]Six powders ([Formula: see text], 20, 25 and 30[Formula: see text]at.%) prepared by mechanical alloying. The X-ray diffraction (XRD) studies indicated that after 72[Formula: see text]h of milling, the solid solution bcc-[Formula: see text]-Fe(Si) is formed. The grain sizes, [Formula: see text]D[Formula: see text] (nm), decreases with increasing Si concentration and reaches a minimum value of 11[Formula: see text]nm. We have found that the lattice parameter decreases with increasing Si concentration. The changes in values are attributed to the substitutional dissolution of Si in Fe matrix. From the adjustment of Mössbauer spectra, we have shown that the mean hyperfine magnetic field, [Formula: see text]H[Formula: see text] (T), decreases with increasing Si concentration. The substitutional dependence of [Formula: see text]H[Formula: see text] (T) can be attributed to the effect of p electrons Si influencing electrons d of Fe.

Phase Development and Dielectric Properties of 0.98BaTiO3-0.02Ba (Mg1/3Nb2/3) O3 Ceramic

2011 ◽  
Vol 700 ◽  
pp. 58-62
Author(s):  
Rachanusorn Roongtao ◽  
Supagorn Rugmai ◽  
Wanwilai C. Vittayakorn
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Loss Factor ◽  
X Ray Diffraction ◽  
Phase Purity ◽  
X Ray ◽  
Phase Development ◽  
Scanning Electron

The 0.98BaTiO3-0.02Ba (Mg1/3Nb2/3) O3ceramics has been synthesized through a conventional mixed-oxide by using BT nanopowder and BMN micropowder. The phase purity of the powders and the ceramics was examined using X-ray diffraction (XRD). The 0.98BT-0.02BMN powders were sintered to 92% of the theoretical density at a temperature of 1300 °C for 2 h. The microstructure of the sintered surface was investigated using scanning electron microscopy (SEM). The dielectric constant (εr) and loss factor (tanδ) of the sintered pellets at Curie temperture were 3000 and 0.015, respectively.

Sign in / Sign up

Export Citation Format

Share Document