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.

Structure
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.

Production
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.

Properties

 * Room temperature entropy – 47.0 cal/deg. mol
 * Dielectric constant – 20 (at 100 kHz)
 * It is hygroscopic and decomposes with swelling in moist air.

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