Low Temperature Hydrothermal Synthesis and Sintering of Ba0.6Sr0.4TiO3

2008 ◽  
Vol 368-372 ◽  
pp. 53-55
Author(s):  
Yun Fei Fu ◽  
Pei Feng Zhang ◽  
Hui Qing Fan ◽  
Xiu Li Chen
Keyword(s):  
Dielectric Constant ◽  
Low Temperature ◽  
Room Temperature ◽  
Hydrothermal Process ◽  
Dielectric Anomaly ◽  
Loss Angle ◽  
Synthesis Mechanism ◽  
Dielectric Constant And Loss ◽  
Different Temperatures ◽  
Bst Ceramics

Ba0.6Sr0.4TiO3 nanopowders (~ 80 nm in size) were prepared by low temperature hydrothermal process. The process and synthesis mechanism were discussed in detail. Furthermore, the powders were pressed into disc-shaped pellets and sintered at different temperatures. The frequency dependence of the dielectric constant and loss angle tangent of the sintered BST ceramics are measured from room temperature to 500°C and a diffuse dielectric anomaly by the dielectric relaxation was found.

BARIUM TITANATE FILMS FOR ELECTRONIC APPLICATIONS: STRUCTURAL AND DIELECTRIC PROPERTIES

2008 ◽  
Vol 15 (03) ◽  
pp. 237-244 ◽  
Author(s):  
S. RIAZ ◽  
S. SHAMAILA ◽  
B. KHAN ◽  
S. NASEEM
Keyword(s):  
Dielectric Constant ◽  
Room Temperature ◽  
Structural Changes ◽  
Sol Gel ◽  
Optical Microscope ◽  
Loss Angle ◽  
Sem Images ◽  
Dielectric Constant And Loss ◽  
Cu Substrates ◽  
Sol Gel Films

Synthesis of the precursors, using research grade materials and locally available facilities, is optimized in order to obtain a suitable sol for BaTiO 3. The optimally synthesized BaTiO 3 sol is then spun onto Cu substrates to obtain films of thickness ~0.5 μm. The deposited BaTiO 3 films are heated up to a temperature of 300°C. Surface and structural changes, with heating, are observed by optical microscope, scanning electron microscope, atomic force microscope, and X-ray diffraction. The surface cracked in some cases but is generally uniform, as seen with SEM and AFM, in case of optimized conditions. The SEM images reveal large crystallites, which are correlated to the XRD observation of tetragonal perovskite structure of these sol–gel films. The AFM scan, however, shows an rms roughness of 35.6 nm for an area of 3 μm × 3 μm. Tetragonal perovskite BaTiO 3 is obtained at a temperature of as low as 300°C. The dielectric constant and loss angle, in the 30 Hz–3 MHz range, are calculated at room temperature and up to 200°C. At high frequencies the dielectric constant (~290) and loss angle (~2 × 10-6) values indicate the usefulness of such films in electronic applications. The leakage current is also measured at room temperature and a conductivity of 2.0 × 10-15 S/cm is obtained.

Synthesis and Characteristics of MgO Coated BST-Mg2TiO4 Composite Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1180-1183
Author(s):  
Qian Qian Jia ◽  
Hui Ming Ji ◽  
Shan Liu ◽  
Xiao Lei Li ◽  
Zheng Guo Jin
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Loss Tangent ◽  
Phase Shifters ◽  
Precipitation Method ◽  
Composite Ceramics ◽  
Low Dielectric ◽  
Dielectric Constant And Loss ◽  
Bst Ceramics

The (Ba, Sr)TiO3 (hereafter BST) ceramics are promising candidate for applying in tunable devices. MgO coated BST-Mg2TiO4 (BSTM-MT) composite ceramics were prepared to obtain the low dielectric constant, low dielectric loss, good dielectric constant temperature stability, and high tunability of BST ceramics. The Ba0.55Sr0.40Ca0.05TiO3 nanoparticles were coated with MgO using the precipitation method and then mixed with Mg2TiO4 powders to fabricate BSTM-MT composite ceramics. The morphologies, phases, elements, and dielectric properties of the sintered ceramics were investigated. The core-shell structure of BST powder wrapped with MgO was clearly observed from the TEM image. After sintered at 1100 °C for 2 h, the composite ceramics expressed dense microstructures from SEM images and two main phases BST and Mg2TiO4 were detected in the XRD patterns. The dielectric constant and loss tangent were both reduced after the coating. The reduced dielectric constant and loss tangent of BSTM-MT were 190, 0.0011 (2MHz), respectively. The ceramics exhibited the diffuse phase transition near the Curie temperature and the Curie temperature shifted from 10 °C to 5 °C after the coating. Since the continuous Ti-O bonds were disconnected with the MgO coating, the tunability was reduced to 15.14 % under a DC bias field of 1.1 kV/mm. The optimistic dielectric properties made it useful for the application of tunable capacitors and phase shifters.

Effect of Forging Temperature on Microstructure and Tensile Properties in Fe3Al-Based Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
Y. Yang ◽  
W. Yan ◽  
J. N. Liu ◽  
S. Hanada
Keyword(s):  
Plastic Deformation ◽  
Low Temperature ◽  
Yield Strength ◽  
Grain Boundaries ◽  
Tensile Properties ◽  
Room Temperature ◽  
Annealing Treatment ◽  
Different Temperatures ◽  
Local Plastic Deformation ◽  
Strength And Ductility

AbstractForging processes at two different temperatures are performed to examine the relation between the microstructure and room temperature tensile properties in a Ce doped Fe3Al-based alloy. Results show that the microstructure and the ductility are sensitive to the forging temperature before annealing treatment. Higher yield strength and ductility can be obtained through forging at a relatively low temperature of 750°C followed by annealing at 800°C and 500°C. It is suggested that the formation of non-equilibrium grain boundaries and banded subgrains within carbide-free areas along grain boundaries enhances the local plastic deformation and results in the improvement of ductility. During the initial deformation at room temperature <111> slip is predominant for both microstructures.

Dielectric Properties of Pulsed Excimer Laser Ablated BaBi2Nb2O9 Thin Films

2002 ◽  
Vol 748 ◽  
Author(s):  
Apurba Laha ◽  
S. B. Krupanidhi ◽  
S. Saha
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Dielectric Constant ◽  
Temperature Dependence ◽  
Loss Tangent ◽  
Dielectric Response ◽  
Room Temperature ◽  
Dielectric Constant And Loss ◽  
Wide Range ◽  
Room Temperature Dielectric Constant

ABSTRACTThe dielectric response of BaBi2Nb2O9 (BBN) thin films has been studied as a function of frequency over a wide range of temperatures. Both dielectric constant and loss tangent of BBN thin films showed a ‘power law’ dependence with frequency, which was analyzed using the Jonscher's universal dielectric response model. Theoretical fits were utilized to compare the experimental results and also to estimate the value of temperature dependence parameters such as n(T) and a(T) used in the Jonscher's model. The room temperature dielectric constant (ε') of the BBN thin films was 214 with a loss tangent (tanδ) of 0.04 at a frequency of 100 kHz. The films exhibited the second order dielectric phase transition from ferroelectric to paraelectric state at a temperature of 220 °C. The nature of phase transition was confirmed from the temperature dependence of dielectric constant and sponteneous polarization,respectively. The calculated Currie constant for BBN thin films was 4 × 105°C.

scholarly journals Sintering Behavior of BST Nanoparticles at Low Temperature and Electrical Properties of their Ceramics

2020 ◽  
Author(s):  
Jianquan Qi ◽  
Yan Li ◽  
Mengyin Li ◽  
Jiahui Xie ◽  
Tianchi Yu ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Dielectric Constant ◽  
Alkaline Earth ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Sintering Behavior ◽  
Sintering Aids ◽  
Bst Ceramics ◽  
Related Compounds ◽  
Alkaline Earth Cations

Abstract The powders of the Ba0.75Sr0.25TiO3 (BST) nanoparticles were directly synthesized by milling of Ba(OH)2·8H2O, Sr(OH)2·8H2O and Ti(BuO)4 in ethanol at room temperature. They have homogenous grains of ~15 nm and the high sintering activity. The dense ceramics with the density >90% can be obtained at a sintering temperature of ≤950 oC by them with adding 3 wt% sintering aids of Bi2O3 and Li2CO3. The sintering behavior of the BST nanoparticles by adding the aids of Bi2O3 and Li2CO3 is studied carefully. Several Bi-related compounds are involved in the sintering procedure at a different temperature. They enhance the mass transfer and promote the sintering densification. These compounds such as Ba2BiO4 and SrBiO4 appear at 800 oC, LiBa4Bi3O11 and Sr1.2Bi0.8O3 appear over 830 oC, and Bi8.11Ba0.89O13.05 appears at 950 oC. The cation Bi in the ceramics has mixture valences of 3+ and 5+. It makes the ceramics as semiconducting state with the dark gray color and decreases the ceramics resistivities. With the sintering temperature increase, especially at 950 oC, the cation Bi tends back to single valence of +3 in the ceramics. The most of alkaline earth cations in Bi-related compounds will release and resorb into the lattice of BST and drive the densification of the nanoparticles. The BST ceramics can have a peak dielectric constant >6500 at 53 oC, loss <0.025, and resistivity >1012 W·cm when sintered at a temperature of ≥900 oC with 3 wt% sintering aids. They have a potential application for multiple layer ceramic capacitors (MLCC) with silver inner-electrodes.

Application of the Measurement of the Dielectric Constant and Loss Angle to the Study of the Structure of Vulcanizates Loaded with Carbon Blacks

1952 ◽  
Vol 25 (3) ◽  
pp. 533-548
Author(s):  
P. Thirion ◽  
R. Chasset
Keyword(s):  
Dielectric Constant ◽  
Carbon Black ◽  
The Other ◽  
Rubber Matrix ◽  
Loss Angle ◽  
Colloidal Structure ◽  
Dielectric Absorption ◽  
Dielectric Loss Angle ◽  
Dielectric Constant And Loss ◽  
The Matrix

Abstract In the case of vulcanizates containing carbon black the variation curves of dielectric loss angle as a function of temperature enable the Debye type absorption occurring in the rubber matrix to be distinguished from a supplementary absorption little influenced by variations in temperature and frequency which is characteristic of blacks possessing a structure. The experimental results obtained indicate no difference in physical or chemical state between the matrix occupying the space between the particles of black in a loaded mix and the vulcanizate of the corresponding pure rubber mix. The supplementary losses on the other hand seem to be closely related to the effects of structure in loaded mixes imagined by Mullins to explain the mechanical behavior of these mixes: they decrease very rapidly by elongation or swelling and give rise to various phenomena of hysteresis. It would seem that dielectric absorption could advantageously be applied as a nondestructive test revealing the colloidal structure of rubber mixes based on carbon black. Moreover the dielectric constant would enable information to be obtained on the form factor and the orientation of the particles or agglomerates of particles of black in mixes on the basis of a theory assimilating these particles (or agglomerates) to condenser armatures.

Dielectric and Magnetic Properties of Sintered Cobalt Ferrite Derived from Nanocrystalline Powders

2012 ◽  
Vol 476-478 ◽  
pp. 726-729 ◽  
Author(s):  
Liang Neng Wu ◽  
Li Zhen Jiang ◽  
Fang Yu Hong
Keyword(s):  
Dielectric Constant ◽  
Magnetic Properties ◽  
Hysteresis Loop ◽  
Loss Tangent ◽  
Room Temperature ◽  
Cobalt Ferrite ◽  
Relative Dielectric Constant ◽  
Nanocrystalline Powders ◽  
Magnetic Characteristics ◽  
Dielectric Constant And Loss

A kind of Cobalt ferrite ceramics were successfully prepared by using nanocrystalline powders synthesized by citrate gel method. The relative dielectric constant and loss tangent of the ceramic as a function of frequency (100 Hz - 1 MHz) was investigated at room temperature. Both of them decrease with increase in frequency showing dispersion. Hysteresis loop magnetization was measured and the ceramic show good magnetic characteristics at room temperature.

Photokapazitiver Effekt und Lumineszenz unter IR-Bestrahlung

1964 ◽  
Vol 19 (4) ◽  
pp. 454-458 ◽  
Author(s):  
Frank Matossi ◽  
Dieter Siebert
Keyword(s):  
Dielectric Constant ◽  
Energy Band ◽  
Infrared Radiation ◽  
Band Model ◽  
Loss Angle ◽  
Capacitance Change ◽  
Effect Change ◽  
Conduction Electrons ◽  
Dielectric Constant And Loss ◽  
Uv Excitation

The photocapacitive effect (change of dielectric constant and loss angle by uv-radiation) is modified by additional infrared radiation either during or after uv excitation. This is investigated in some detail for a phosphor with photodielectric effect where the capacitance change is essentially due to polarization of filled traps. There are indications for the influence of reversible occupation changes among traps. Results with a phosphor whose capacitance change is due to conduction electrons are not yet conclusive with respect to a detailed energy band model; they show, however, that both conduction band and valence band participate in the processes.

Investigation of Low Temperature Sintering of Low Voltage Varistor Based on TiO2

2014 ◽  
Vol 852 ◽  
pp. 12-16 ◽  
Author(s):  
De Jun Lan ◽  
Shu Quan Wan
Keyword(s):  
Dielectric Constant ◽  
Low Temperature ◽  
Room Temperature ◽  
Low Voltage ◽  
Structural Characteristics ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Low Temperature Sintering ◽  
Powder Xrd Analysis ◽  
Room Temperature Dielectric Constant

Low temperature sintering of TiO2-base varistor was systematically investigated through doing with V2O5 and B-Si glass. Pellets prepared could be densely sintered from 1273 to 1473K. The highest relative density, 94.6%, was found in the sample sintered at 1433K. According to I-V plots of ceramic pellets, the nonlinear coefficient α and breakdown voltage V1mA were obtained and found to be α=2~5 and V1mA=15~30V. The room temperature dielectric constant was very large, high as to about 20000. Powder XRD analysis has shown the desirable macro-structural characteristics of these compacts.

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