Barium titanate
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| Barium titanate | |
|---|---|
| Identifiers | |
| CAS number | [12047-27-7] |
| Properties | |
| Molecular formula | BaTiO3 |
| Molar mass | 233.192 g/mol |
| Appearance | white crystals |
| Density | 6.02 g/cm3, solid |
| Melting point |
1625 °C |
| Solubility in water | insoluble |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Barium titanate is an oxide of barium and titanium with the chemical formula BaTiO3. It is a ferroelectric ceramic material, with a photorefractive effect and piezoelectric properties. It has five phases as a solid, listing from high temperature to low temperature: hexagonal, cubic, tetragonal, orthorhombic, and rhombohedral crystal structure. All of the structures exhibit the ferroelectric effect except cubic.
Contents |
[edit] Appearance
It has the appearance of a white powder or transparent crystals. It is insoluble in water and soluble in concentrated sulfuric acid. Its risk and safety phrases are R20/22, S28A, S37, and S45.
[edit] Manufacture
Barium titanate can be manufactured by liquid phase sintering of barium carbonate and titanium dioxide, optionally with other materials for doping.
High purity barium titanate powder is reported to be a key component of new barium titanate capacitor energy storage systems being developed by EEStor for use in electric vehicles.[1]
Barium titanate is often mixed with strontium titanate.
[edit] Uses
Barium titanate is used as a dielectric material for ceramic capacitors, and as a piezoelectric material for microphones and other transducers. As a piezoelectric material, it was largely replaced by lead zirconate titanate, also known as PZT.
Polycrystalline barium titanate displays positive temperature coefficient, making it a useful material for thermistors and self-regulating electric heating systems.
Fully-dense nanocrystalline barium titanate has 40% higher permittivity than the same material prepared in classic ways.[2]
Barium titanate crystals find use in nonlinear optics. The material has high beam-coupling gain, and can be operated at visible and near-infrared wavelengths. It has the highest reflectivity of the materials used for self-pumped phase conjugation (SPPC) applications. It can be used for continuous-wave four-wave mixing with milliwatt-range optical power. For photorefractive applications, barium titanate can be doped by various other elements, e.g. cerium.[3]
The addition of inclusions of barium titanate to tin has been shown to create a bulk material with a higher viscoelastic stiffness than that of diamonds. Barium titanate goes through two phase transitions that change the crystal shape and volume. This leads to composites where the barium titanates have a negative bulk modulus (Young's modulus), meaning that when a force acts on the inclusions, there is displacement in the opposite direction, further stiffening the composite.[4]
Thin films of barium titanate display electrooptic modulation to frequencies over 40 GHz.[5]
The pyroelectric and ferroelectric properties of barium titanate are used in some types of uncooled sensors for thermal cameras.
[edit] See also
[edit] References
- ^ http://www.zenncars.com/investor/releases/Certification_EEStor_01_16_2007.pdf
- ^ http://research.ucdavis.edu/NCD.cfm?ncdid=658[1]
- ^ http://www.redoptronics.com/Ce:BaTiO3-crystal.html Ce:BaTiO3
- ^ http://www.sciencemag.org/cgi/content/abstract/315/5812/620 [2]
- ^ http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-24-5962 [3]
