Barium titanate

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Barium Titanate
General
Other names
Molecular formula BaTiO3
Molar mass 233.192 g/mol
Appearance white crystals
Crystal Structure tetragonal
CAS number [12047-27-7]
Properties
Density and phase 6.02 g/cm3, solid
Solubility in water insoluble
Melting point 1625 °C
Boiling point
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 four phases as a solid, listing from high temperature to low temperature: 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 sintering of barium carbonate and titanium dioxide, optionally with other materials for doping.

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 an 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.[1]

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 continouos-wave four-wave mixing with milliwatt-range optical power. For photorefractive applications, barium titanate can be doped by various other elements, eg. cerium.[2]

The addition of inclusions of barium titanate to tin has been shown to create a bulk material with a 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.[3]

Thin films of barium titanate display electrooptic modulation to frequencies over 40 GHz.[4]

The pyroelectric and ferroelectric properties of barium titanate are used in some types of uncooled sensors for thermal cameras.

[edit] See also

[edit] References

  1. ^ http://research.ucdavis.edu/NCD.cfm?ncdid=658[1]
  2. ^ http://www.redoptronics.com/Ce:BaTiO3-crystal.html Ce:BaTiO3
  3. ^ http://www.sciencemag.org/cgi/content/abstract/315/5812/620 [2]
  4. ^ http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-24-5962 [3]

[edit] External links


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