Barium orthotitanate

Barium orthotitanate is the inorganic compound with the chemical formula Ba₂TiO₄. It is a colourless solid that is of interest because of its relationship to barium titanate, a useful electroceramic.

The solid has two known phases: a low-temperature (β) phase with P2₁/n symmetry and a high-temperature (α′) phase with P2₁nb symmetry. The structure of Ba₂TiO₄ is unusual among the titanates because its titanium atoms sit in a four-oxygen tetrahedron rather than a six-oxygen octahedron.

It forms as white crystals from a melt of BaCl₂, BaCO₃ and TiO₂ or from just sintering BaCO₃ and TiO₂. Another method of preparation is heating pellets of Ba(OH)₂ and TiO₂. Additionally, there are polymer precursor, sol-gel and reverse micellar routes to Ba₂TiO₄ synthesis. Ba₂TiO₄ has also been successfully grown as a thin film with chemical vapor deposition.

Barium orthotitanate can remove up to 99.9% of CO
2 from a high-temperature gas stream by the reaction:

...
Wikipedia