Barium titanate

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Barium Titanate
Image:Barium titanate.jpg
General
Other names
Molecular formula	BaTiO₃
Molar mass	233.192 g/mol
Appearance	white crystals
Crystal Structure	tetragonal
CAS number	[12047-27-7] [3]
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.

1 Appearance
2 Manufacture
3 Uses
4 See also
5 References
6 External links

[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, Template: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]

Thin films of barium titanate display electrooptic modulation to frequencies over 40 GHz.^[3]