Barium Carbonate

BaCo3

Chemistry

BaO77.660

Volatiles

CO222.340

Significant Temperatures

Hazards

Miscellaneous

Notes

Barium carbonate powder is dense and white and is manufactured either from the mineral barite (BaSO4) or from barium chloride. Subsequently a precipitation process is used to get the carbonate form. There are several crystalline forms of BaCO3, alpha is the most stable.

Barium carbonate is very stable thermally and does not readily disassociate unless at least some CO is available in the kiln atmosphere (i.e. reduction). BaCO3 is reduced to the unstable BaCO2 in the reaction:

BaCO3 + CO -> BaCO2 + CO2

BaCO2 will break down much more readily into BaO for glass building (BaCO3 will however decompose readily during glaze melting in a reduction atmosphere). The carbonate will dissolve into the melt intact if present in small amounts (e.g. 5% or less). Even if present in larger amounts, the glaze matrix can solidify with both types, one acting as a flux; the other as a refractory filler, opacifier and matting agent (especially in low temperature glazes). Effects produced when baria is acting as a filler are sometimes mistaken for those of a true baria crystal matte. Such will likely leach toxic BaO (other oxides will opacify or produce a low fire matte i.e. CaO, MgO, Alumina, Zircon).

Barium carbonate produces gases as it decomposes and these can sometimes cause many pinholes or blisters in glazes. There are many barium frits available and incorporating one of them to source the BaO instead is a classic application of ceramic chemistry calculations. The resultant glaze will be more fusible and will have better clarity and fewer defects.

In art ceramics barium carbonate is popular for the production of classic barium crystal mattes. These are dependent on adequate kiln temperatures and a slightly reducing atmosphere to decompose the material to yield BaO.

Barium carbonate is commonly added to clay bodies in small amounts (0.2-0.8%) to halt fired surface scumming or efflorescence It is slightly soluble in water and provides Ba++ ions to link with SO4-- ions in the water to form BaSO4 (barium sulfate). This new sulfate molecular form is much less soluble (2-3 mg/L), so it stays internal (rather than migrating to the surface during drying).

Some quote melting temperature as 1350C.


Properties

Data

Linked Articles

URLs

Suppliers

Authors

XML

<?xml version="1.0" encoding="UTF-8"?>
<material name="Barium Carbonate" descrip="BaCo3" generic="1" rawmineral="0" searchkey="Barium Carb, Witherite" loi="22.30">
<families>
<family name="Flux Source"/>
</families>
<regions>
<region name="North America"/>
</regions>
<oxides>
<oxide symbol="BaO" name="Barium Oxide, Baria" status="" percent="77.660" tolerance=""/>
</oxides>
<volatiles>
<volatile symbol="" name="" percent="22.340" tolerance=""/>
</volatiles>
<hazards>
<hazard name="Barium"/>
</hazards>
<temperatures>
<temperature temperature="1360C" notes="Melts"/>
<temperature temperature="900C" notes="Decomposes"/>
</temperatures>
<suppliers>
<supplier name="Generic" country="" url="" label=""/>
</suppliers>
<notes>
<note>Barium carbonate powder is dense and white and is manufactured either from the mineral barite (BaSO4) or from barium chloride. Subsequently a precipitation process is used to get the carbonate form. There are several crystalline forms of BaCO3, alpha is the most stable.

Barium carbonate is very stable thermally and does not readily disassociate unless at least some CO is available in the kiln atmosphere (i.e. reduction). BaCO3 is reduced to the unstable BaCO2 in the reaction:

BaCO3 + CO -&gt; BaCO2 + CO2

BaCO2 will break down much more readily into BaO for glass building (BaCO3 will however decompose readily during glaze melting in a reduction atmosphere). The carbonate will dissolve into the melt intact if present in small amounts (e.g. 5% or less). Even if present in larger amounts, the glaze matrix can solidify with both types, one acting as a flux; the other as a refractory filler, opacifier and matting agent (especially in low temperature glazes). Effects produced when baria is acting as a filler are sometimes mistaken for those of a true baria crystal matte. Such will likely leach toxic BaO (other oxides will opacify or produce a low fire matte i.e. CaO, MgO, Alumina, Zircon).

Barium carbonate produces gases as it decomposes and these can sometimes cause many pinholes or blisters in glazes. There are many barium frits available and incorporating one of them to source the BaO instead is a classic application of ceramic chemistry calculations. The resultant glaze will be more fusible and will have better clarity and fewer defects.

In art ceramics barium carbonate is popular for the production of classic barium crystal mattes. These are dependent on adequate kiln temperatures and a slightly reducing atmosphere to decompose the material to yield BaO.

Barium carbonate is commonly added to clay bodies in small amounts (0.2-0.8%) to halt fired surface scumming or efflorescence It is slightly soluble in water and provides Ba++ ions to link with SO4-- ions in the water to form BaSO4 (barium sulfate). This new sulfate molecular form is much less soluble (2-3 mg/L), so it stays internal (rather than migrating to the surface during drying).

Some quote melting temperature as 1350C.
</note>
</notes>
<testdata>
<testitem testname="0" value="4.27"/>
<testitem testname="0" value="4.27"/>
</testdata>
</material>


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