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In order to decrease dielectric losses of PZT type piezoelectric ceramics, it is necessary to introduce oxygen vacancies in ABO3 perovskite lattice by heterovalent cationic substitutions (for instance Fe, Mn, Ni in place of B ions). Hence, it is possible, at room temperature, to reduce the dielectric loss by an order of magnitude of corresponding stoichiometric materials. This phenomenon is accompanied by an increase of electric conductivity which appears especially at temperatures higher than hundred degrees. This conductivity is very depending on the fabrication process and the result is an important lack of reliability during the industrial manufacture. This is certainly due to a mobility of charges which is the result of the existence of oxygen vacancies. The partial introduction of fluorine into the lattice can greatly reduce the losses and increase the polarization stability under high stress levels. This study concerns the mechanism of the fluorine introduction and its consequences on electric and piezoelectric properties of ceramics with oxygen vacancies.
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