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ZrO 2 and TiO 2 modified lead-free (K 0.5 Na 0.5 )NbO 3 (KNN) piezoelectric ceramics are prepared by conventional solid-state reaction. The effect of acceptor doping on structural and functional properties are investigated. A decrease in the Curie temperature and an increase in the dielectric constant values are observed when doping. More interestingly, an increase in the coercive field E c and remanent polarization P r is observed. The piezoelectric properties are greatly increased when doping with small concentrations dopants. ZrO 2 doped ceramic exhibits good piezoelectric properties with piezoelectric coefficient d 33 =134 pC/N and electromechanical coupling factor k p =35%. It is verified that nonlinearity is significantly reduced. Thus, the creation of complex defects capable of pinning the domain wall motion is enhanced with doping, probably due to by the formation of oxygen vacancies.These results strongly suggest that compositional engineering using low concentrations of acceptor doping is a good means of improving the functional properties of KNN lead-free piezoceramic system.

The stoichiometry, polymorphism, and electrical behaviour of the solid solutions Pr 0.5+x−y Bi y Li 0.5−3x TiO 3 with perovskitelike structure have been studied. Data are given as a solid solution triangle, XRD patterns for two polymorphs T and O, the composition dependence of their parameters, and ionic conductivity plots. A region of perovskite-like solid solutions was obtained when the bismuth content in the general formula Pr 0.5+x−y Bi y Li 0.5−3x TiO 3 was y Յ 0.10 and the lithium IntroductionThere has been much recent interest in the development of novel ionic conductors as solid electrolytes in lithium batteries.[1Ϫ12] Fast ionic conductors with the general formula RE 0.5ϩx Li 0.5Ϫ3x TiO 3 , where RE ϭ La, Pr, Nd, and Sm have been reported, [7Ϫ12] for which the maximum conductivity was for the La series (1.1·10Ϫ3 S·cm Ϫ1 for x ϭ 0.07 at room temperature). [7] More recently the phase diagram, crystal chemistry, and ionic conductivity of the system La 0.5ϩxϪy Bi y Li 0.5Ϫ3x TiO 3 have been reported.[13] The compounds of this system are ionic conductors whose conductivity increases as the amount of lithium increases, up to x ϭ 0.075, but decreases when the amount of bismuth increases. The system with Bi needs less time in the thirst treatment at 1250°C than a similar system without bismuth. [13] We aimed to investigate the stoichiometry range, crystal chemistry, and electrical behaviour of materials of the general formula Pr 0.5ϩxϪy Bi y Li 0.5Ϫ3x TiO 3 and to establish the phase diagram at room temperature of the system Pr 0.67 TiO 3 /Pr 0.5 Li 0.5 TiO 3 /Bi 0.5 Li 0.5 TiO 3 . XRD patterns of perovskites with different Li and Bi contents have been analyzed and a study of the thermal treatment time with the [a] content was 0.033 Յ x Յ 0.133. The compounds are mixed conductors. With increasing amounts of lithium the ionic conductivity first increased, reached a maximum for x = 0.20, with a conductivity at 25°C of 6.639·10 −3 S·cm −1 , and then decreased.

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