China
Africa
Explore chapters and articles related to this topic
Ceramics and Composites
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
Why do some ceramic materials such as barium titanate possess high dielectric constants? Barium titanate is a ferroelectric material, consisting of permanent electrostatic dipoles (analogous to magnetic dipoles in a magnetic material). In the absence of an external field, these permanent dipoles organize themselves into domains of various random orientations so as to minimize the total electrostatic energy. When an electric field E is applied, domains with the favorable orientation grow at the expense of those not in the favorable orientation, thus increasing the net dipole moment per unit volume (known as polarization P). The aligned dipoles increase the overall electric field. The ratio of this overall electric field within the material to the original applied field is the dielectric constant. It can be shown from standard electrostatics that the dielectric constant ε is given by: ε=1+PεoE
Synthesis of Solids
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
Barium titanate (BaTiO3) is a ferroelectric material (Chapter 9) that is widely used in capacitors because of its high dielectric constant. It was initially prepared by heating barium carbonate and titanium dioxide at high temperature BaCO3(s)+TiO2(s)=BaTiO3(s)+CO2(g).
Actuator Materials
Published in Kenji Uchino, Micro Mechatronics, 2019
Barium titanate (BaTiO3) is one of the most thoroughly studied and most widely used piezoelectric materials. Just below the Curie temperature (130°C), the material has tetragonal symmetry and the spontaneous polarization is directed along [001]. Below 5°C, the material is orthorhombic and the polarization is oriented along [011]. At −90°C, a transition to a rhombohedral phase occurs and the polarization direction is along [111]. The electromechanical properties of ceramic BaTiO3 are affected by the stoichiometry and microstructure of the material, as well as the presence of dopants on both the A and B sites of the perovskite lattice. Ceramic BaTiO3 has been modified with dopants such as Pb or Ca in order to stabilize the tetragonal phase over a wider temperature range. These compositions were originally designed for use in Langevin-type piezoelectric vibrators, and have currently been revived as commercial products for this and a variety of other applications because of the current trend toward Pb-free piezoelectrics.
Study of dielectric behavior of ternary composites of epoxy-barium titanate with iron oxide and ferrite in the band (DC-12.5 GHz)
Published in Inorganic and Nano-Metal Chemistry, 2021
Tarek Arab, Habib Khouni, Nacerdine Bouzit, Juan Pablo Martínez Jiménez
Spinel ferrites of general formula MFe2O4, where M represents a divalent cation such as Ni, Co, Cu, Zn, Fe or Mg, belong to a structure known as Fd3M of face-centered cubic symmetry, the elementary mesh of which measures approximately 80 nm and haves 32 oxygen ions developing octahedral (B) and tetrahedral (A) sites, the 8 tetrahedral sites and the 16 octahedral sites are occupied by metal cations. The simplest model of ferrite is the magnetite Fe3O4 which is therefore written: (Fe3+)[Fe2+, Fe3+]O4. The mesh of spinel Fe3O4 is faces centered cubic (fcc). This network has two kinds of interstitial sites, tetrahedral sites (or A sites) surrounded by four oxygen atoms, and octahedral sites (or B sites) surrounded by six oxygen atoms. Barium titanate (BaTiO3) has a cubic perovskite structure.
Enhanced electric field-induced strain and electrostrictive response of lead-free BaTiO3-modified Bi0.5(Na0.80K0.20)0.5TiO3 piezoelectric ceramics
Published in Journal of Asian Ceramic Societies, 2021
Pharatree Jaita, Parkpoom Jarupoom
Among various lead-free materials, barium titanate (BaTiO3 or BT) is one of the most widely studied lead-free ferroelectric material due to its superior properties, that is, high dielectric constant, high electromechanical coupling factor (k33), and low dielectric loss characteristics [18]. The BT ceramic was the first oxide perovskite type ferroelectric material developed and thoroughly studied, ever since its discovery more than 60 years ago [19,20]. It has been well recognized as the first ferroelectric oxide that has been utilized to the manufacture electronic components and studied by three independent Japanese, Russian, and American teams since 1943 [21,22]. At temperature greater than 120°C, BT ceramic has a paraelectric with cubic phase. In the temperature ranging 5 – 120 °C, the tetragonal ferroelectric phase with the tetragonality (c/a) ratio of ~ 1.01 was obtained. It is an important ceramic material for the electronic and memory devices [18].
Ferroelectric studies for soft Gd-modified PZT ceramics
Published in Phase Transitions, 2018
S. C. Panigrahi, Piyush R. Das, R. N. P. Choudhary
The early discovery of ferroelectricity in some compounds, such as (i) Rochelle salt {NaK(C4H4O6)·4H2O}, (ii) the perovskite group such as barium titanate (BaTiO3), (iii) potassium dihydrogen phosphate (KH2PO4) [1], etc., has motivated researchers to study compounds of similar and/or different structural families in the search of new ferroelectric materials for device applications. Now-a-days lead-free piezoelectric ceramics have been actively investigated but at present they are deficient to completely replace lead-base ceramics which shows huge advantages in real application. Some lead-based compounds of perovskite and other structural families have been found very useful for piezoelectric, pyroelectric and other device applications. Lead zirconate titanate {Pb (Zr, Ti) O3} with different Zr/Ti ratios (abbreviated as PZT) is one of the lead-based ceramics which has extensively been studied by many researchers because of its unique features such as non-hygroscopicity, mechanical strength, high-sensitivity and simplicity of preparation with their excellent piezoelectric, pyroelectric, dielectric and electro-optic properties. Such ceramic material possesses distinct characteristics that make the materials suitable for various applications such as FRAM, MEMS, charge storage, transducer, oscillators, pyroelectric devices, actuators and sensors [2–8].