Barium borate

Barium borate

Names
Other names barium diborate, barium boron oxide, barium metaborate
Identifiers
CAS Number	13701-59-2 Y 26124-86-7 (monohydrate) N 23436-05-7 (dihydrate) N
3D model (JSmol)	Interactive image
ChemSpider	3642855 Y
ECHA InfoCard	100.033.824
EC Number	237-222-4
PubChem CID	6101043 23165673 (monohydrate)
UNII	5SE5SRJ05N
InChI InChI=1S/2BO2.Ba/c2*2-1-3;/q2*-1;+2 Y Key: QBLDFAIABQKINO-UHFFFAOYSA-N Y InChI=1/2BO2.Ba/c2*2-1-3;/q2*-1;+2 Key: QBLDFAIABQKINO-UHFFFAOYAX
SMILES [Ba+2].[O-]B=O.[O-]B=O
Properties
Chemical formula	BaB2O4 or Ba(BO2)2
Molar mass	222.95
Appearance	white powder or colorless crystals
Odor	odorless
Density	3.85 g/cm3
Melting point	1,095 °C (2,003 °F; 1,368 K)
Solubility in hydrochloric acid	soluble
Refractive index (nD)	ne = 1.5534, no = 1.6776
Structure
Crystal structure	Rhombohedral, hR126
Space group	R3c, No. 161
Lattice constant	a = 1.2529 nm, c = 1.274 nm
Hazards
Safety data sheet	MSDS
GHS pictograms
GHS signal word	Warning
GHS hazard statements	H302
GHS precautionary statements	P264, P270, P301+312, P330, P501
Flash point	Non-flammable
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 borate is an inorganic compound, a borate of barium with a chemical formula BaB₂O₄ or Ba(BO₂)₂. It is available as a hydrate or dehydrated form, as white powder or colorless crystals. The crystals exist in the high-temperature α phase and low-temperature β phase, abbreviated as BBO; both phases are birefringent, and BBO is a common nonlinear optical material.

Barium borate exists in two major crystalline forms: alpha and beta. The low-temperature beta phase converts into the alpha phase upon heating to 925 °C. β-Barium borate (BBO) differs from the α form by the positions of the barium ions within the crystal. Both phases are birefringent, however the α phase possesses centric symmetry and thus does not have the same nonlinear properties as the β phase.

Alpha barium borate, α-BaB₂O₄ is an optical material with a very wide optical transmission window from about 190 nm to 3500 nm. It has good mechanical properties and is a suitable material for high-power ultraviolet polarization optics. It can replace calcite, titanium dioxide or lithium niobate in Glan–Taylor prisms, Glan–Thompson prisms, walk-off beam splitters and other optical components. It has low hygroscopicity, and its Mohs hardness is 4.5. Its damage threshold is 1 GW/cm² at 1064 nm and 500 MW/cm² at 355 nm.

Beta barium borate, β-BaB₂O₄, is a nonlinear optical material transparent in the range ~190–3300 nm. It can be used for spontaneous parametric down-conversion. Its Mohs hardness is also 4.5.