The chemical formula for Barium Titanate is BaTiO3. As a powder it is white to grey in colour and has a perovskite structure.
It is soluble in many acids including sulfuric, hydrochloric and hydrofluoric acids. It is insoluble in alkalis and water.
In the pure form it is an electrical insulator. However, when doped with small amounts of metals, most notably scandium, yttrium, neodymium, samarium etc it becomes semiconducting.
As a semiconductor it exhibits positive temperature of co-efficient of resistivity (PTCR) properties in the polycrystalline form. This means at a certain temperature, called the Curie temperature, the material will exhibit an increase in resistivity, the increase typically being several orders of magnitude. The Curie temperature can to some extent be controlled by the dopant.
At the Curie temperature, barium titanate undergoes a phase change from tetrahedral to cubic. It has also been reported that single crystals of barium titanate exhibit negative temperature co-efficient of resistivity (NTCR) properties.
Barium titanate also exhibits ferroelectric properties and is an excellent photorefractive material.
Due to its PTCR properties, barium titanate is most often found used as a thermistor e.g. in thermal switches.
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