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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has been studied. Using powder X-ray diffraction, five distinct areas have been found in the triangle Bi 0.5 Li 0.5 TiO 3 /La 2/3 -TiO 3 /La 0.5 Li 0.5 TiO 3 . A region of perovskite-like solid solutions was obtained when the bismuth content in the general formula La 0.5+x−y Bi y Li 0.5−3x TiO 3 was less than y = 0.10. Two

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