Barium titanate

Barium titanate

Polycrystalline BaTiO3 in plastic
Identifiers
CAS Number	12047-27-7 Y
3D model (Jmol)	Interactive image
ChemSpider	10605734 Y
ECHA InfoCard	100.031.783
PubChem CID	6101006
RTECS number	XR1437333
InChI InChI=1S/2Ba.4O.Ti/q2*+2;4*-1; Y Key: JRPBQTZRNDNNOP-UHFFFAOYSA-N Y InChI=1/2Ba.4O.Ti/q2*+2;4*-1;/r2Ba.O4Ti/c;;1-5(2,3)4/q2*+2;-4 Key: JRPBQTZRNDNNOP-NXYSCRTKAD
SMILES [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-]
Properties
Chemical formula	BaTiO3
Molar mass	233.192 g
Appearance	white crystals
Odor	odorless
Density	6.02 g/cm3, solid
Melting point	1,625 °C (2,957 °F; 1,898 K)
Solubility in water	insoluble
Solubility	slightly soluble in dilute mineral acids; dissolves in concentrated hydrofluoric acid
Band gap	3.2 eV (300 K, single crystal)
Refractive index (nD)	no2.412; ne=2.360
Structure
Crystal structure	Tetragonal, tP5
Space group	P4mm, No. 99
Hazards
R-phrases	R20/22
S-phrases	S28A, S37, and S45
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Barium titanate is the inorganic compound with the chemical formula BaTiO₃. Barium titanate is a white powder and transparent as larger crystals. This titanate is a ferroelectric ceramic material, with a photorefractive effect and piezoelectric properties. It is used in capacitors, electromechanical transducers and nonlinear optics.

The solid can exist in five phases, listing from high temperature to low temperature: hexagonal, cubic, tetragonal, orthorhombic, and rhombohedral crystal structure. All of the phases exhibit the ferroelectric effect except the cubic phase. The high temperature cubic phase is easiest to describe, consisting of octahedral TiO₆ centres that define a cube with Ti vertices and Ti-O-Ti edges. In the cubic phase, Ba²⁺ is located at the center of the cube, with a nominal coordination number of 12. Lower symmetry phases are stabilized at lower temperatures, associated with the movement of the Ba²⁺ to off-center position. The remarkable properties of this material arise from the cooperative behavior of the Ba²⁺ centres.

Barium titanate can be synthesized by the relatively simple sol–hydrothermal method. Barium titanate can also be manufactured by heating barium carbonate and titanium dioxide. The reaction proceeds via liquid phase sintering. Single crystals can be grown around 1100 °C from molten potassium fluoride. Other materials are often added for doping, e.g. to give solid solutions with strontium titanate. Reacts with nitrogen trichloride and produces a greenish or grey mixture, the ferroelectric properties of the mixture are still present in this form.