{{#if:222.95odorlessodorlesswhite solidBaB2O4 or Ba(BO2)23.85 g/cm31060 °Chydrochloric acidsoluble|! style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Barium borate
CAS number 13701-59-2 YesY
26124-86-7 (monohydrate),
23436-05-7 (dihydrate)
ChemSpider 3642855 YesY
EC number 237-222-4
Jmol-3D images Image 1
Molecular formula BaB2O4 or Ba(BO2)2
Molar mass 222.95
Appearance white solid
Odor odorless
Density 3.85 g/cm3
Melting point

1060 °C

Solubility in hydrochloric acid soluble

Flash point Non-flammable
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Barium borate, also called barium diborate, barium boron oxide, barium metaborate, or (as an optical crystal) BBO (BaB2O4 or Ba(BO2)2) is an inorganic compound, a borate of barium. It is available as a hydrate or dehydrated.

How are they made?

Barium borate

Barium borate can be prepared by reaction of an aqueous solution of boric acid with barium hydroxide. The prepared γ-BBO contains water of crystallization that can not be completely removed by drying at 120 °C. Dehydrated γ-BBO can be prepared by heating to 300-400 °C. Calcination at about 600-800 °C causes complete conversion to β-BBO. BBO prepared by this method does not contain trace amounts of BaB2O2[1]

Barium borate monohydrate

Barium borate monohydrate (white powder) is prepared from the solution of barium sulfide and sodium tetraborate. It is used as an additive to e.g. paints as flame retardant, mold inhibitor, and corrosion inhibitor. It is also used as a white pigment.

Barium borate dihydrate

Barium borate dihydrate is prepared from the solution of sodium metaborate and barium chloride at 90-95 °C. After cooling to room temperature, white powder is precipitated. Barium borate dihydrate loses water at above 140 °C. It is used as a flame retardant for paints, textiles, and paper.[2]

Alpha barium borate

Alpha barium borate, α-BaB2O4, the high-temperature phase, is an optical material with high birefringence and very wide optical transmission window from about 189 nm to 3500 nm. It has good mechanical properties and is a suitable material for high-power ultraviolet polarization optics.[3] It can replace calcite, titanium dioxide, lithium niobate, etc. in Glan-Taylor prisms, Glan-Thompson prisms, walk-off beam splitters, etc. It is low-hygroscopic, its Mohs hardness is 4.5. Its damage threshold is 1 GW/cm2 at 1064 nm and 500 MW/cm2 at 355 nm. Its density is 3.85 g/cm3.[4]

Beta barium borate

Beta barium borate, β-BaB2O4, is a nonlinear optical material. Thin films of BBO can be prepared by MOCVD from barium(II) hydro-tri(1-pyrazolyl)borate. Different phases can be obtained depending on deposition temperatures.[5] Thin films of beta-barium borate can be prepared by sol-gel synthesis.[6]


Barium borate is a biocide registered in USA since 1960 as a broad-spectrum bactericide and fungicide. It is added to paints, coatings, adhesives, plastics, and paper and paper products.

Barium borate is resistant to moisture and ultraviolet radiation. It can act as UV stabilizer for polyvinyl chloride.[7]

The solubility of barium borate is a disadvantage when used as a pigment. Silica-coated powders are available. The alkaline properties and the anodic passivation properties of the borate ion enhance the anticorrosion performance. Commonly available barium metaborate pigment comes in three grades; Grade I is a barium metaborate itself, grade II is compounded with 27% zinc oxide, and grade III is compounded with 18% of zinc oxide and 29% calcium sulfate. Barium borate shows synergistic performance with zinc borate.[8]

Alpha (and to less degree beta) barium borate crystals can be used as neutron detectors.

Barium borate is used as a flux in some barium titanate and lead zirconate EIA Class 2 dielectric ceramic formulations for ceramic capacitors, in amount of about 2%. The barium-boron ratio is critical for flux performance; BaB2O2 content adversely affects the performance of the flux.[1][9]

Beta barium borate crystals for nonlinear optics can be grown from fluxed melt of BBO, sodium oxide and sodium chloride.[10]

Barium borate-fly ash glass can be used as radiation shielding. Such glasses are superior in performance to concrete and to other barium borate glasses.[11]


  1. 1.0 1.1 Ross, Sidney D. "Barium borate preparation" U.S. Patent 4,897,249 issued January 30, 1990
  2. Script error
  3. Alpha Barium Borate
  4. Barium Borate (a-BBO) Crystal
  5. http://direct.bl.uk/bld/PlaceOrder.do?UIN=219729443&ETOC=RN&from=searchengine
  6. Script error
  7. Koskiniemi, Mark S "Calcium pyroborate as a microbicide for plastics" U.S. Patent 5,482,989 issued 01/09/1996
  8. Script error
  9. Script error
  10. Gualtieri, Devlin M.; Chai, Bruce H. T. "High temperature solution growth of barium borate (BaB2 O4 )" U.S. Patent 4,931,133 issued June 5, 1990
  11. Script error