Barium orthotitanate is the inorganic compound with the chemical formula Ba<sub>2</sub>TiO<sub>4</sub>. 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 (ò) phase with P2<sub>1</sub>/n symmetry and a high-temperature (ñ) phase with P2<sub>1</sub>nb symmetry. The structure of Ba<sub>2</sub>TiO<sub>4</sub> 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 BaCl<sub>2</sub>, BaCO<sub>3</sub> and TiO<sub>2</sub> or from just sintering BaCO<sub>3</sub> and TiO<sub>2</sub>. Another method of preparation is heating pellets of Ba(OH)<sub>2</sub> and TiO<sub>2</sub>. Additionally, there are polymer precursor, sol-gel and reverse micellar routes to Ba<sub>2</sub>TiO<sub>4</sub> synthesis. Ba<sub>2</sub>TiO<sub>4</sub> has also been successfully grown as a thin film with chemical vapor deposition.
Barium orthotitanate can remove up to 99.9% of from a high-temperature gas stream by the reaction: