Abstract
The microstructure and electrical properties of calcium-modified barium titanate ceramics of compositions (Ba 1-x Ca x )TiO 3 have been investigated. From the influence of the CaO content and stoichiometry on the said characteristics of the materials, it is concluded that the cationic ratio, α=(Ba+Ca)/Ti, is the predominant factor affecting the resistance of materials against the reducing sintering atmosphere. The electrical properties, including resistivity and dielectric dispersion, can be completely preserved when the sintering atmosphere is switched from air to H 2 /N 2 , but only for samples with values of α greater than unity. The formation of a hexagonal BaTiO 3-δ phase, which consumes the oxygen vacancies, is presumed to be the factor that improves the resistance of these materials against the reducing sintering atmosphere.