Novel Doping Mechanism for Very‐High‐Permittivity Barium Titanate Ceramics

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Abstract
Barium titanate (BaTiO 3 ) can be doped with La 3+ ions via partial substitution for Ba 2+ ions; charge balance is maintained by the creation of Ti 4+ vacancies. Samples processed in an atmosphere of 1 bar O 2 and a temperature of 1350°C are insulating and free from electronic defects associated with either O 2 loss or reduction of Ti 4+ to Ti 3+ . The Curie temperature ( T c ) decreases approximately linearly as the lanthanum content increases and, at the same time, an increase in the permittivity (ɛ′) maximum at T c occurs. For the composition Ba 1‐ x La x Ti 1‐ x /4 O 3 , where x = 0.05, ɛ′ has a maximum value of 19000 at 18°C, compared with a typical value of 10000 at 130°C in undoped BaTiO 3 ceramics. This value is the highest value reported for A‐site‐doped BaTiO 3 and is linked to the mechanism of combined A‐site doping and Ti‐vacancy creation.

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