scholarly journals Scale-Dependent Dielectric Properties in BaZr0.05Ti0.95O3 Ceramics

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4386
Author(s):  
Leontin Padurariu ◽  
Vlad-Alexandru Lukacs ◽  
George Stoian ◽  
Nicoleta Lupu ◽  
Lavinia Petronela Curecheriu
Keyword(s):  
Finite Element Method ◽  
Grain Size ◽  
Finite Element ◽  
Dielectric Properties ◽  
Critical Size ◽  
Grain Sizes ◽  
Maximum Value ◽  
Doped Barium Titanate ◽  
Numerical Finite Element ◽  
Titanate Ceramics

In the present work, BaZr0.05Ti0.95O3 ceramics with grain sizes between 0.45 and 135 µm were prepared by solid-state reaction and classical sintering. The effect of grain size on dielectric properties was systematically explored, and it was found that dielectric permittivity reaches a maximum value for grain sizes between 1.5 and 10 µm and then rapidly drops for larger grain sizes. A numerical finite element method was employed to eliminate the effect of porosity on the effective values of permittivity. The results indicate that it is possible to have a critical size in slightly doped barium titanate ceramics with enhanced functional properties for a grain size between 1.5 and 10 µm.

Microstructure Evolution and Dielectric Properties of Nb/Mn and Dy/Mn Doped Barium Titanate Ceramics

2006 ◽  
Vol 518 ◽  
pp. 229-234 ◽  
Author(s):  
Ljiljana Živković ◽  
V. Paunović ◽  
M. Miljković ◽  
Momcilo M. Ristić
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Solid State ◽  
High Dielectric Constant ◽  
Dopant Content ◽  
Doped Barium Titanate ◽  
High Dielectric ◽  
Titanate Ceramics ◽  
Mn Doped

Nb/Mn and Dy/Mn codoped BaTiO3 specimens, prepared by conventional solid-state procedure, were investigated regarding their microstructural and dielectric properties. The powders were doped with Nb2O5 and Dy2O3 with an amount of 0.1, 0.5 and 1.0 at% of dopants ions. The MnO content of 0.05 at% Mn was the same in both types of samples. The specimens were sintered in air at 1320 and 1350 °C for two hours. Microstructural and compositional studies were done by SEM equipped with EDS. In low doped BaTiO3 the grain size is around 1-3 μm, while in ceramics with high dopant content (1.0 at%) the grain size distribution was in the range of 3-10 μm. High dielectric constant is associated with small-grained microstructure, being 5000 for Dy-doped and 6500 for Nb-doped BaTiO3 sintered at 1350 °C. The specimens with low dopant content demonstrate the Curie-Weiss behavior in a paraelectric regime. A nearly flat permittivity response with temperature was obtained for specimens with 0.5 and 1.0 at% Dy content. Loss tangents were in the range of 0.03 - 0.32.

Computation on continuous grain refinement in AA1050 aluminum during repetitive tube expansion and shrinking technique

2015 ◽  
Vol 232 (4) ◽  
pp. 307-318
Author(s):  
H Jafarzadeh ◽  
K Abrinia
Keyword(s):  
Finite Element Method ◽  
Plastic Deformation ◽  
Grain Size ◽  
Finite Element ◽  
Dislocation Density ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Half Cycle ◽  
Tube Expansion ◽  
Element Method

The microstructure evolution during recently developed severe plastic deformation method named repetitive tube expansion and shrinking of commercially pure AA1050 aluminum tubes has been studied in this paper. The behavior of the material under repetitive tube expansion and shrinking including grain size and dislocation density was simulated using the finite element method. The continuous dynamic recrystallization of AA1050 during severe plastic deformation was considered as the main grain refinement mechanism in micromechanical constitutive model. Also, the flow stress of material in macroscopic scale is related to microstructure quantities. This is in contrast to the previous approaches in finite element method simulations of severe plastic deformation methods where the microstructure parameters such as grain size were not considered at all. The grain size and dislocation density data were obtained during the simulation of the first and second half-cycles of repetitive tube expansion and shrinking, and good agreement with experimental data was observed. The finite element method simulated grain refinement behavior is consistent with the experimentally obtained results, where the rapid decrease of the grain size occurred during the first half-cycle and slowed down from the second half-cycle onwards. Calculations indicated a uniform distribution of grain size and dislocation density along the tube length but a non-uniform distribution along the tube thickness. The distribution characteristics of grain size, dislocation density, hardness, and effective plastic strain were consistent with each other.

Preparation of barium titanate ceramics from amorphous fine particles of the Ba–Ti–O system and its dielectric properties

1995 ◽  
Vol 10 (2) ◽  
pp. 306-311 ◽  
Author(s):  
S. Wada ◽  
T. Suzuki ◽  
T. Noma
Keyword(s):  
Dielectric Properties ◽  
Barium Titanate ◽  
Curie Temperature ◽  
Decomposition Method ◽  
Fine Particles ◽  
Nitrate Solution ◽  
Pressing Method ◽  
Calcination Temperatures ◽  
Grain Sizes ◽  
Titanate Ceramics

Using titanium nitrate solution stabilized by chelation, amorphous fine particles of the Ba-Ti-O system were prepared by the mist decomposition method in air. After calcination of these particles, barium titanate ceramics were prepared using the hot uniaxial pressing method, and various properties were investigated. As a result, the grain sizes could be controlled over the range from 58 nm to 187 nm by the sintering temperatures and/or the calcination temperatures, keeping the density almost constant. Moreover, the dielectric properties of the samples showed that the relative permittivity decreased with decreasing grain size, and Curie temperature also shifted to lower temperatures in the same way. In this study, we first found that Curie temperature existed in the barium titanate ceramics with grain sizes from 58 to 147 nm.

Effects of phase composition and grain size on the piezoelectric properties of HfO2-doped barium titanate ceramics

2019 ◽  
Vol 54 (19) ◽  
pp. 12392-12400
Author(s):  
Hong-Mei Yin ◽  
Wen-Jun Xu ◽  
Heng-Wei Zhou ◽  
Xing-Yu Zhao ◽  
Yi-Neng Huang
Keyword(s):  
Grain Size ◽  
Phase Composition ◽  
Barium Titanate ◽  
Piezoelectric Properties ◽  
Doped Barium Titanate ◽  
Titanate Ceramics

Grain Size Dependence of the Microstructure and Dielectric Properties of Potassium Niobate-Barium Titanate Ceramics

2013 ◽  
Vol 566 ◽  
pp. 34-37
Author(s):  
Kenta Yamashita ◽  
Ichiro Fujii ◽  
Kouichi Nakashima ◽  
Nobuhiro Kumada ◽  
Yoshihiro Kuroiwa ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Barium Titanate ◽  
Size Dependence ◽  
Potassium Niobate ◽  
Titanate Ceramics

In this study, 0.8 KNbO3(KN) -0.2 BaTiO3(BT) ceramics were prepared using KN powder with the diameter of 100 nm and BT powders with the diameter of 100, 300, or 500 nm. The relative densities were more than 96 % of the theoretical densities of the samples. The dielectric constant of the samples was temperature-stable at temperatures between-50 and 300 °C and it was found that the dielectric constant of the 0.8KN-0.2BT ceramics increased as the BT diameter increased.

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