Barium titanate 3219865 224182703 2008-07-07T18:23:25Z 200.89.166.45 {{Chembox new | Name = Barium titanate | ImageFile = <!-- | ImageSize = 200px --> | ImageName = Barium titanate | OtherNames = | Section1 = {{Chembox Identifiers | CASNo = 12047-27-7 }} | Section2 = {{Chembox Properties | Formula = BaTiO<sub>3</sub> | MolarMass = 233.192 g/mol | Appearance = white crystals | Density = 6.02 g/cm<sup>3</sup>, solid | Solubility = insoluble | MeltingPt = 1625 °C | BoilingPt = }} }} '''Barium titanate''' is an [[oxide]] of [[barium]] and [[titanium]] with the [[chemical formula]] BaTiO<sub>3</sub>. 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. == 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}}, {{S28}}A, {{S37}}, and {{S45}}. ==Manufacture== Barium titanate can be manufactured by liquid phase [[sintering]] of [[barium carbonate]] and [[titanium dioxide]], optionally with other materials for [[doping (semiconductors)|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.<ref>http://www.zenncars.com/investor/releases/Certification_EEStor_01_16_2007.pdf</ref> Barium titanate is often mixed with [[strontium titanate]]. ==Uses== Barium titanate is used as a [[dielectric]] material for ceramic [[capacitor]]s, and as a piezoelectric material for [[microphone]]s and other [[transducer]]s. 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 [[thermistor]]s and self-regulating electric heating systems. Fully-dense nanocrystalline barium titanate has 40% higher [[permittivity]] than the same material prepared in classic ways.<ref>http://research.ucdavis.edu/NCD.cfm?ncdid=658[http://research.ucdavis.edu/NCD.cfm?ncdid=658]</ref> 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]].<ref>http://www.redoptronics.com/Ce:BaTiO3-crystal.html [http://www.redoptronics.com/Ce-BaTiO3-crystal.html Ce:BaTiO<sub>3</sub>]</ref> 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.<ref>http://www.sciencemag.org/cgi/content/abstract/315/5812/620 [http://www.sciencemag.org/cgi/content/abstract/315/5812/620]</ref> [[Thin film]]s of barium titanate display [[Electro-optic modulator|electrooptic modulation]] to frequencies over 40&nbsp;GHz.<ref>http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-24-5962 [http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-24-5962]</ref> The pyroelectric and ferroelectric properties of barium titanate are used in some types of uncooled sensors for [[thermal camera]]s. ==See also== * [[Strontium titanate]] * [[Lead zirconate titanate]] ==References== <references/> ==External links== * [http://blog.wired.com/gadgets/2007/09/instant-charge-.html EEStor's "instant-charge" capacitor batteries] [[Category:Titanates]] [[Category:Barium compounds]] [[Category:Ceramic materials]] [[Category:Piezoelectric materials]] [[Category:Infrared sensor materials]] [[Category:Nonlinear optical materials]] [[ar:تيتانات باريوم]] [[de:Bariumtitanat]] [[es:Titanato de bario]] [[ja:チタン酸バリウム]] [[zh:钛酸钡]]