Barium titanate. (BaTiO3) is an inorganic compound, white and transparent powder in the form of larger crystals. It is a ferroelectric ceramic material, with piezoelectric properties and a photoretractive effect.
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- 1 Appearance
- 2 Properties
- 1 Properties of ferroelectric materials:
- 3 Obtaining
- 4 Applications
- 5 Sources
It has the appearance of white powder or translucent crystals. It is not soluble in water, but it is in concentrated sulfuric acid.
Considered as a prototype material within ferroelectrics. It is the most studied from the basic point of view, both experimental and theoretical, due to its varied physical properties. It has a high dielectric constant, and a low loss factor. (Isolating material).
The properties of barium titanate are strongly influenced by the presence of defects, especially oxygen vacancies.
Through suitable modifications of the properties of the grains and the grain edges, very interesting characteristics are obtained for many applications.
Properties of ferroelectric materials:
1- They have spontaneous polarization (This is in the absence of an external field).
2- Under the action of a field, we can reverse its polarization: (P -P)
3- They have polarization domains.
4- They undergo ferroelectric-paraelectric transitions.
Barium titanate can be obtained by liquid phase sintering of barium carbonate and titanium dioxide.
It can be made by heating barium carbonate and titanium dioxide . The reaction takes place through liquid phase sintering. Single crystals can be grown in 1100 C of molten potassium fluoride . Other materials are often added by doping, for example to give solid solutions with strontium titanate .
Reacts with nitrogen trichloride and produces a green or gray mixture, the ferroelectric properties of the mixture are still present in this form.
Much work has been devoted to its morphology. Fully dense nanocrystalline barium titanate has 40% higher permittivity than the same material prepared in classical forms. The addition of barium titanate inclusions to tin has been used to produce a bulk material with a higher viscoelastic stiffness than that of diamonds. Barium titanate goes through two phase transitions that change the shape of the crystals and the volume. This phase change leads to compounds where the barium titanates have a negative bulk modulus, which means that when a force acts on the inclusions, there is a displacement in the opposite direction, further stiffening the compound.
Like many oxides, barium titanate is insoluble in water but attacked by sulfuric acid. Its largest band gap at room temperature is 3.2 eV, but increases to ~ 3.5 eV when the particle size is reduced from about 15 to 7 Nm.
It is used in capacitors. It is a piezoelectric material for microphones and other transducers. The spontaneous polarization of barium titanate is approximately 0.15 C / m2 at room temperature and its Curie point is 120 C. As a piezoelectric material it was largely replaced by [[Lead Zirconate Titanate]], also known like PZT. Polycrystalline barium titanate shows a positive temperature coefficient, making it a useful material for self-regulating electric thermistors and heating systems.
Barium titanate crystals find use in nonlinear optics. The material has high coupling beam 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 applications. It can be used for continuous wave mixing of four waves with milliwatt-range optical power.
For photorefractive applications, barium titanate can be doped by various other elements, for example iron.
The pyroelectric and ferroelectric properties of barium titanate are used in some types of non-cooled sensors for thermal cameras.
The high purity of barium titanate powder is a key component of new energy storage systems for use in electric vehicles.