scholarly journals Dielectric properties of La/Mn codoped barium titanate ceramics

2016 ◽  
Vol 29 (2) ◽  
pp. 285-296 ◽  
Author(s):  
Vesna Paunovic ◽  
Vojislav Mitic ◽  
Milos Marjanovic ◽  
Ljubisa Kocic
Keyword(s):  
Dielectric Properties ◽  
Pechini Method ◽  
Local Area ◽  
Dissipation Factor ◽  
Curie Constant ◽  
Weiss Temperature ◽  
Fine Grained ◽  
Average Grain Size ◽  
Titanate Ceramics ◽  
La Doped

La/Mn codoped BaTiO3 ceramics with various La2O3 content, ranging from 0.3 to 1.0 at% La, were investigated regarding their microstructure and dielectric properties. The content of MnO2 was kept constant at 0.01 at% Mn in all samples. La/Mn codoped and undoped BaTiO3 were obtained by a modified Pechini method and sintered in air at 13000C for two hours. The homogeneous and completely fine-grained microstructure with average grain size from 0.5 to 1.5mm was observed in samples doped with 0.3 at% La. In high doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed. The dielectric properties were investigated as a function of frequency and temperature. The dielectric permittivity of the doped BaTiO3 was in the range of 3945 to 12846 and decreased with an increase of the additive content. The highest value for the dielectric constant at room temperature (er= 12846) and at the Curie temperature (er= 17738) were measured for the 0.3 at% La doped samples. The dissipation factor ranged from 0.07 to 0.62. The Curie constant (C), Curie-Weiss temperature (T0) and critical exponent (g) were calculated using the Curie-Weiss and the modified Curie-Weiss law. The highest values of Curie constant (C=3.27?105 K) was measured in the 1.0 at% La doped samples. The obtained values for g ranged from 1.04 to 1.5, which pointed out the sharp phase transformation from the ferroelectric to the paraelectric phase.

scholarly journals Enhanced dielectric properties in la modified barium titanate ceramics

2019 ◽  
Vol 32 (2) ◽  
pp. 179-193 ◽  
Author(s):  
Vesna Paunovic ◽  
Zoran Prijic ◽  
Milos Djordjevic ◽  
Vojislav Mitic
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dissipation Factor ◽  
Dielectric Constants ◽  
Phase Transformation Temperature ◽  
Average Grain Size ◽  
La Doped

Donor/acceptor (La/Mn) doped BaTiO3 ceramics, sintered at different temperatures, were studied regarding their microstructure and dielectric properties as well as the dielectric response in a ferroelectric/paraelectric regime. The concentrations of La3+ as donor, ranging from 0.1 to 5.0 at% were used for doping, while a content of Mn4+ as acceptor was at 0.05 at% in all samples. The sintering temperature of codoped samples were 1290? and 1350?C. A reduction in grain size and fine-grained microstructure with average grain size from 0.5 to 2.0 mm was observed in low doped samples, whereas the abnormal growth of individual grains took place in the 2 at% and 5 at% La doped specimens. The dielectric properties of these samples were investigated as a function of frequency (100Hz - 20 kHz) and temperature (20-180?C). The measured results suggested that both the dielectric constants of the ceramics (er at room temperature and ermax at the Curie temperature) decreased as the concentration of La3+ increased. The dielectric permittivity was in the range of 944 to 3200. For samples doped with 0.1 at% La and sintered at 1350?C, the highest dielectric constant value at room temperature (er= 3200) and Curie temperature (er= 5000) were measured. For all measured samples the dissipation factor was less than 0.09. With an increase in La contents, dielectric measurements exhibited shift in the Curie temperature (Tc) towards the low temperature. Using the Curie-Weiss and the modified Curie-Weiss law, Curie's constant C was calculated as well as the parameterg, which describes the deviation from the linear dependence er of T above the phase transformation temperature. The calculated values for g ranged from 1.01 to 1.43. These values indicate a sharp phase transformation in lowdoped and diffuse phase transformation in highly La doped samples. The phase transition was reflected in the values of C that started to decrease with increasing dopant content.

scholarly journals Electrical characterization and impedance response of lanthanum doped barium titanate ceramics

2008 ◽  
Vol 40 (3) ◽  
pp. 283-294 ◽  
Author(s):  
D. Mancic ◽  
V. Paunovic ◽  
M. Vijatovic ◽  
B. Stojanovic ◽  
Lj. Zivkovic
Keyword(s):  
Dielectric Permittivity ◽  
Pechini Method ◽  
Electrical Characterization ◽  
Dissipation Factor ◽  
Electrical Circuit ◽  
Impedance Response ◽  
Modified Pechini Method ◽  
Titanate Ceramics ◽  
Constant Phase Elements ◽  
La Doped

The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT) to 350?C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300?C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%.

Dielectric properties of fine‐grained barium titanate ceramics

1985 ◽  
Vol 58 (4) ◽  
pp. 1619-1625 ◽  
Author(s):  
G. Arlt ◽  
D. Hennings ◽  
G. de With
Keyword(s):  
Dielectric Properties ◽  
Barium Titanate ◽  
Fine Grained ◽  
Titanate Ceramics

Effect of grain size and mechanical processing on the dielectric properties of BaTiO3

1995 ◽  
Vol 10 (6) ◽  
pp. 1418-1423 ◽  
Author(s):  
B.W. Lee ◽  
K.H. Auh
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Domain Switching ◽  
External Pressure ◽  
Coarse Grained ◽  
One Dimensional ◽  
Fine Grained ◽  
Average Grain Size ◽  
Coarse Grained Material

Dielectric properties of polycrystalline BaTiO3 ceramics having grain sizes of 1 to 40 μm have been studied. Fine-grained ceramic BaTiO3 of 1 μm average grain size has 90°domains and has shown higher dielectric constant, lower ferroelectric transition temperature (Tc), and lower transition energy than coarser-grained material. 90°domain switching was preferentially produced in the fine-grained BaTiO3 as a result of abrasion. For the fine-grained BaTiO3, the dielectric constant decreased with one-dimensional pressure, whereas, for the coarse-grained material, the dielectric constant increased before decreasing with the pressure. The one-dimensional pressure resulted in increased Tc of both the fine- and coarse-grained BaTiO3, with the effect being the greatest for the coarse-grained material. The relationship between these results and internal stress, and the effect of external pressure imposed on internally stressed lattice, were discussed.

Structural and dielectric properties of La-doped lead titanate ceramics

2004 ◽  
Vol 39 (6) ◽  
pp. 867-872 ◽  
Author(s):  
M. Kellati ◽  
S. Sayouri ◽  
N. El Moudden ◽  
M. Elaatmani ◽  
A. Kaal ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Lead Titanate ◽  
Titanate Ceramics ◽  
La Doped

Influence of Lanthanum on Microstructure and Dielectric Properties of Barium Titanate Ceramics by Solid State Reaction

2011 ◽  
Vol 412 ◽  
pp. 275-279 ◽  
Author(s):  
Wei Cai ◽  
Chun Lin Fu ◽  
Ze Bin Lin ◽  
Xiao Ling Deng ◽  
Wei Hai Jiang
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Dielectric Loss ◽  
Barium Titanate ◽  
Lattice Constant ◽  
Solid State Reaction ◽  
Lanthanum Content ◽  
Doped Barium Titanate ◽  
Titanate Ceramics ◽  
La Doped

La-doped barium titanate ceramics with 0~1.0 at.% La2O3 were prepared by conventional solid state reaction method. The crystal structure and dielectric properties of La-doped barium titanate ceramics were investigated. Lanthanum ions have entered the unit cell and substituted for Ba2+ ions on the A sites of perovskite structure. The a-axis lattice constant increases and the c-axis lattice constant decreases as lanthanum content increases. Addition of lanthanum leads to the fall of the Curie temperature of La-doped BTO ceramics. There are two different doping mechanisms for La-doped BTO ceramics. The dielectric loss of BTO ceramics with 0.3 at.% La2O3 is higher than that of pure BTO ceramics. When lanthanum content is above 0.5 at.%, the dielectric loss of La-doped BTO ceramics decrease with the increasing of lanthanum content. The result of dielectric constant as a function of temperature at different frequencies indicates that La-doped BTO ceramics are not relaxor ferroelectrics but ferroelectrics with diffuse phase transition.

Microwave Dielectric Properties of Lanthanide Titanate Ceramics

1993 ◽  
Vol 32 (Part 1, No. 9B) ◽  
pp. 4327-4331 ◽  
Author(s):  
Junichi Takahashi ◽  
Keisuke Kageyama ◽  
Kouhei Kodaira
Keyword(s):  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric ◽  
Titanate Ceramics

scholarly journals Investigation on the Microstructure of ECAP-Processed Iron-Aluminium Alloys

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 219
Author(s):  
Bernd-Arno Behrens ◽  
Kai Brunotte ◽  
Tom Petersen ◽  
Roman Relge
Keyword(s):  
Grain Refinement ◽  
Aluminium Alloys ◽  
Aluminium Content ◽  
Microstructure Development ◽  
Chamber Furnace ◽  
Fine Grained ◽  
Angular Pressing ◽  
Ecap Process ◽  
Average Grain Size ◽  
Forming Temperature

The present work deals with adjusting a fine-grained microstructure in iron-rich iron-aluminium alloys using the ECAP-process (Equal Channel Angular Pressing). Due to the limited formability of Fe-Al alloys with increased aluminium content, high forming temperatures and low forming speeds are required. Therefore, tool temperatures above 1100 °C are permanently needed to prevent cooling of the work pieces, which makes the design of the ECAP-process challenging. For the investigation, the Fe-Al work pieces were heated to the respective hot forming temperature in a chamber furnace and then formed in the ECAP tool at a constant punch speed of 5 mm/s. Besides the chemical composition (Fe9Al, Fe28Al and Fe38Al (at.%—Al)), the influences of a subsequent heat treatment and the holding time on the microstructure development were investigated. For this purpose, the average grain size of the microstructure was measured using the AGI (Average Grain Intercept) method and correlated with the aforementioned parameters. The results show that no significant grain refinement could be achieved with the parameters used, which is largely due to the high forming temperature significantly promoting grain growth. The holding times in the examined area do not have any influence on the grain refinement.

Dielectric properties of fine-grained BaTiO3 prepared by spark-plasma-sintering

2004 ◽  
Vol 83 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Baorang Li ◽  
Xiaohui Wang ◽  
Longtu Li ◽  
Hui Zhou ◽  
Xingtao Liu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Spark Plasma Sintering ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma
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