scholarly journals An Investigation of the Electrical Behavior of Thermally Sprayed Aluminum Oxide

1996 ◽  
Author(s):  
C.J. Swindeman ◽  
R.D. Seals ◽  
W.P. Murray ◽  
M.H. Cooper ◽  
R.L. White
Keyword(s):  
Electrical Properties ◽  
Aluminum Oxide ◽  
Dielectric Constants ◽  
Electrical Behavior ◽  
X Ray Diffraction ◽  
Heating And Cooling ◽  
Thermally Sprayed Aluminum ◽  
Plasma Sprayed ◽  
And Control ◽  
Steel Substrates

Abstract Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 °C. High purity (>99.5 wt% pure Al2O3) alumina powders were plasma-sprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 °C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the importance of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.

Ionic Conductivities of Doped CeO2 Thin Films as Related to Their Microstructure

1995 ◽  
Vol 411 ◽  
Author(s):  
Chunyan Tian ◽  
Siu-Wai Chan
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Ionic Conductivities ◽  
Dielectric Constants ◽  
Grain Structure ◽  
X Ray Diffraction ◽  
Fine Grain ◽  
Brick Layer Model ◽  
Columnar Grain ◽  
Beam Deposition

ABSTRACTThin films of 4% Y2O3 doped CeO2/Pd film/(001)LaA103 with a very low pinhole density were successfully prepared using electron-beam deposition technique. The microstructure of the films was characterized by x-ray diffraction and the electrical properties were studied as a function of temperature with AC impedance spectroscopy. A brick layer model was adopted to correlate the electrical properties to the microstructure of the films, which can be simplified as either a series or a parallel equivalent circuit associated with either a fine grain or a columnar grain structure, respectively. The conductivities of the films fell between the conductivities derived from the two circuit models, suggesting that the films are of a mixed fine grain and columnar grain structure. The measured dielectric constants of the films were found smaller than that of the bulk.

Thermal Shock Resistance of Plasma Sprayed Multi-Layered Functionally Graded Cr3C2-NiCr Coatings

2016 ◽  
Vol 852 ◽  
pp. 1000-1005 ◽  
Author(s):  
Dong Xing Fu ◽  
Jing Na Liu ◽  
Er Bao Liu ◽  
Zhao Bin Cai ◽  
Xiu Fang Cui ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Functionally Graded ◽  
X Ray Diffraction ◽  
Coating Materials ◽  
Heating And Cooling ◽  
Structure Of Coatings ◽  
Functionally Graded Coatings ◽  
Shock Resistance ◽  
Plasma Sprayed

The interface properties of multi-layered functionally graded Cr3C2-NiCr coatings deposited by plasma spraying technique were experimentally studied in this paper. The microstructure and phase structure of coatings were studied with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The thermal shock resistance was investigated by cyclic heating and cooling tests using an electro-calefaction furnace. The crack appearances of the coatings were observed carefully. Results show that the plasma sprayed multi-layered functionally graded coatings are compact and the adhesion between the layers and the substrate is good. The coatings have better macro-hardness than the substrate, and the 6-layers coating has the highest macro-hardness and the best wear resistance. Besides, the micro-hardness of coatings increases with increasing content of Cr2C3 in coating materials. Results of cyclic thermal shock show that the main failure styles of the coatings are crack and desquamation and the thermal shock resistance of the coatings is improved obviously by increasing the number of coating layers.

Thermophysical characterization of oil sands: 3. Electrical properties

1981 ◽  
Vol 18 (4) ◽  
pp. 742-750 ◽  
Author(s):  
M. Das ◽  
R. Thapar ◽  
K. Rajeshwar ◽  
J. DuBow
Keyword(s):  
Electrical Properties ◽  
Oil Sands ◽  
Activation Energies ◽  
Dielectric Constants ◽  
Relaxation Processes ◽  
Electrical Behavior ◽  
Frequency Range ◽  
Oil Sand ◽  
Dipole Relaxation ◽  
Mobile Charges

The electrical behavior of oil sand samples from the Athabasca, N. W. Asphalt Ridge, P. R. Spring, and Circle Cliffs deposits was studied in the frequency range 50 Hz – 103 MHz at ambient temperature and up to 550 °C. Anomalously high dielectric constants (ε′) were measured for these samples at low frequencies (<1 kHz) and at elevated temperatures (>200 °C). Accumulation of mobile charges at the phase boundaries in the oil sand matrix was probably responsible for this effect. These mobile charges were presumably created by thermal fragmentation of oil sand bitumen. The anomalous increase in the low-frequency (50 Hz – 1 MHz) ε′ values at temperatures above 150 °C was also traced to interfacial polarization effects. Dipole relaxation behavior was observed for the various samples at frequencies below ~1 kHz and in the temperature range 150–470 °C. Two distinct relaxation processes were identified. The low-temperature (150–400 °C) process had activation energies for dipole orientation ranging from 4.0 to 9.0 kJ/mol depending on the oil sand specimen. The second relaxation process, which occurred at temperatures above 400 °C, had significantly higher activation energies (30–34 kJ/mol). The occurrence of these dipole relaxation peaks may be relevant in the use of electrical techniques to map the location of pyrolysis zones in in situ oil sand retorts. Measurements on the Athabasca samples in the high-frequency range (1–103 MHz) revealed distinct changes in the dielectric parameters associated with the loss of water from the oil sand matrix. The electrical behavior of oil sands is represented in terms of an equivalent circuit model comprising discrete RC elements corresponding to various components in the oil sand matrix. Such a representation was found to aid in an assignment of the observed changes in the electrical properties with frequency and temperature to distinct physical or chemical processes occurring in the oil sand matrix.

Ferroelectric nanocomposite with high dielectric constants

2002 ◽  
Vol 755 ◽  
Author(s):  
Mai T.N. Pham ◽  
B.A. Boukamp ◽  
H.J.M. Bouwmeester ◽  
D.H.A. Blank
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Ferroelectric Material ◽  
Metallic Phase ◽  
Dielectric Constants ◽  
Effective Dielectric Constant ◽  
X Ray Diffraction ◽  
Non Volatile Memory ◽  
Colloidal Method ◽  
High Dielectric

ABSTRACTComposites between ferroelectric material and a dispersed metal phase are of great interest due to the improvement in dielectric properties for such applications as high capacitance capacitors, non-volatile memory, ect. Using a colloidal method, Pt particles with a size of 3–5 nm were dispersed homogeneously in a PZT (PbZr0.53Ti0.43O3) matrix. No unwanted reaction phase between PZT and Pt during sintering at 1150 °C could be detected by X-ray diffraction. Electrical properties were investigated by impedance spectroscopy measurement. The effective dielectric constant increased remarkably as a power function of Pt volume content and can be described by the percolation theory. At 25 vol.% of Pt the dielectric constant of the composite is 4 times larger than that of pure PZT. The temperature dependence of the electrical properties is also influenced by the metallic phase fraction.

Effect of Sm2O3 on the Electrical Properties of TiO2-Ta2O5-Based Capacitor-Varistor Ceramics

2011 ◽  
Vol 213 ◽  
pp. 246-249
Author(s):  
Tian Guo Wang ◽  
Qun Qin ◽  
Dong Jian Zhou
Keyword(s):  
Rare Earth ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Rare Earth Oxide ◽  
Dielectric Constants ◽  
Second Phase ◽  
Electrical Behavior ◽  
Effective Boundary ◽  
Electrical Permittivity ◽  
Change Of Microstructure

TiO2 ceramics doped with 0.1 mol% Ta2O5 and different concentrations of rare earth oxide Sm2O3 were obtained by sintering at 1450 °C. As a varisor material, the microstructure, the nonlinear electrical behavior and dielectric properties of these ceramics were investigated. SEM and XRD were carried out to study the change of microstructure. The results show that there exist second phase (Sm2Ti2O3) on the surface on the surface of TiO2 grains. The ceramics have nonlinear coefficients of α = 2.0-4.0 and ultrahigh relative dielectric constants which is up to 104. The sample doped with 0.5 mol% Sm2O3 exhibits high nonlinear constant of 3.7, low breakdown voltage of 21.5 v/mm, ultrahigh electrical permittivity of 4.25× 104 and low tanδ of 0.37. It is suggested that the sample doped with 0.5 mol% Sm2O3 forms the most effective boundary barrier layer. The defects theory was introduced to illustrate the nonlinear electrical behavior of TiO2-Ta2O5-Sm2O3 varistor ceramics.

Microstructure and properties of PbZr0.6Ti0.4O3 and PbZrO3 thin films deposited on template layers

2000 ◽  
Vol 15 (9) ◽  
pp. 1962-1971 ◽  
Author(s):  
R. E. Koritala ◽  
M. T. Lanagan ◽  
N. Chen ◽  
G. R. Bai ◽  
Y. Huang ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Chemical Vapor ◽  
Dielectric Constants ◽  
Breakdown Field ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
X Ray ◽  
Si Substrates ◽  
Antiferroelectric Phase

Polycrystalline Pb(ZrxTi1−x)O3 thin films with x = 0.6 and 1.0 were deposited at low temperatures (450–525 °C) on (111)Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition. The films were characterized by x-ray diffraction, electron microscopy, and electrical measurements. The texture of the films could be improved by using one of two template layers: PbTiO3 or TiO2. Electrical properties, including dielectric constants, loss tangents, polarization, coercive field, and breakdown field, were also examined. PbZrO3 films on Pt/Ti/SiO2/Si with a pseudocubic (110) orientation exhibited an electric-field-induced transformation from the antiferroelectric phase to the ferroelectric phase. The effect of varying processing conditions on the microstructure and electrical properties of the films is discussed.

scholarly journals An investigation of the electrical behavior of thermally-sprayed aluminum oxide

1996 ◽  
Author(s):  
C.J. Swindeman ◽  
R.D. Seals ◽  
R.L. White ◽  
W.P. Murray ◽  
M.H. Cooper
Keyword(s):  
Aluminum Oxide ◽  
Electrical Behavior ◽  
Thermally Sprayed Aluminum ◽  
Thermally Sprayed

Effect of CeO2 on the Electrical Properties of Ta2O5-Doped TiO2 Capacitor-Varistor Ceramics

2011 ◽  
Vol 214 ◽  
pp. 168-172 ◽  
Author(s):  
Tian Guo Wang ◽  
Qun Qin ◽  
Wen Jun Zhang
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Dielectric Constants ◽  
Electrical Behavior ◽  
Optimal Doping ◽  
Doped Tio2 ◽  
Nonlinear Properties ◽  
Ceramic Sintering ◽  
Electrical Permittivity

TiO2 varistors doped with 0.1 mol% Ta and different concentrations of CeO2 were obtained by ceramic sintering processing at 1400 °C. The effect of CeO2 on the nonlinear electrical behavior and dielectric properties of the Ta2O5-doped TiO2 ceramics were investigated. The nonlinear current (I)-voltage (V) characteristics of TiO2 are examined when doped with small quantities (0.1-0.9 mol%) of CeO2. It is found that CeO2 affects the electrical properties and the dielectric properties of the TiO2-based varistors. The samples have the nonlinear coefficients (α) values of (3.0-5.0), breakdown voltages (10-30 V/mm) and ultrahigh dielectric constants which is up to 105. A small quantities of CeO2 can improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 99.4 mol% TiO2 - 0.1 mol% Ta2O5 - 0.30 mol% CeO2 was obtained with low breakdown voltage of 14.2 V/mm, high nonlinear constant of 4.5 , an ultrahigh electrical permittivity of 8.381.22×105 (measured at 1 kHz) and low tanδ of 0.32, which is consistent with the highest grain boundary barriers of the ceramics. The theory of defects in the crystal lattice was introduced to explain the nonlinear electrical behavior of the CeO2-doped TiO2-based varistor ceramics.

scholarly journals The Effect of Heat Treatment on the Microstructure and Phase Composition of Plasma Sprayed Al2O3 and Al2O3-TiO2 Coatings for Applications in Biomass Firing Plants

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1289
Author(s):  
Airingas Šuopys ◽  
Liutauras Marcinauskas ◽  
Viktorija Grigaitienė ◽  
Romualdas Kėželis ◽  
Mindaugas Aikas ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Phase Composition ◽  
Steel Substrate ◽  
Atmospheric Pressure Plasma ◽  
X Ray Diffraction ◽  
Before And After ◽  
Al2o3 Phase ◽  
Tio2 Coatings ◽  
Plasma Sprayed ◽  
Steel Substrates

This study presents the thermal and chemical resistance of plasma-sprayed Al2O3 and Al2O3 doped with 13 wt.% of TiO2 coatings and their suitability for the fire grate of straw pellet furnaces. Coatings were deposited on steel substrates using direct current atmospheric pressure plasma spraying. The surface structure, elemental, and phase composition of formed coatings were analyzed before and after the thermal treatment, imitating natural application conditions. For the experiment, the annealing temperature was 500 °C for twenty-five cycles (80 min each). It was found that the steel substrate oxidized after five thermal cycles, and the formation of iron oxides was observed. The elemental composition of the Al2O3 and Al2O3-13 wt.% TiO2 coatings remained unchanged even after 25 cycles of heat treatment. The X-ray diffraction (XRD) results revealed that the alpha-Al2O3 to gamma-Al2O3 phase ratio in the Al2O3-TiO2 coating was reduced by only 8.7% after 25 cycles.

Residual Stress Characteristics of Plasma Sprayed CoNiCrAlY Coatings by X-Ray Diffraction

2007 ◽  
Vol 353-358 ◽  
pp. 495-498 ◽  
Author(s):  
Hiroyuki Waki ◽  
Akira Kobayashi
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Plasma Spraying ◽  
Expansion Coefficient ◽  
Bending Test ◽  
Powder Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plasma Sprayed ◽  
Steel Substrates

Plasma sprayed CoNiCrAlY coating can prevent oxidation and corrosion of turbine blades in a gas turbine plant. Cracking and delamination of coatings are affected by the residual stresses in the coatings. In this study, the arising mechanism of residual stress in the plasma sprayed coating was discussed. The residual stresses in CoNiCrAlY coatings were measured by X-ray diffraction method. The coatings were deposited by either low pressure plasma spraying (LPPS) or atmospheric plasma spraying (APS). Each elastic constant which was used for determining the X-ray stress constant was mechanically measured by a bending test. Two kinds of substrates were prepared for each coating in order to examine the effect of thermal expansion coefficient of a substrate. Results were as follows. The residual stresses of the coatings on steel substrates were tensile. On the other hand, the residual stresses on stainless substrates were lower than those on steel substrates. Arising mechanism of the residual stresses can be explained by both the linear expansion coefficient and the range of changing temperature. It was also found that the absolute residual stresses were affected by the spraying powder size and increased with a decrease of the spraying powder size. It was principally caused by the difference in the elastic constants.

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