Chemical insertion in the perovskite solid solutions Pr _0.5+x-yLi_0.5-3xBi_y□_2xTiO ₃: Implications on the electrical properties

Chemical insertion and de-insertion of lithium in pellet samples of the solid solutions Pr_0.5+x-yLi _0.5-3xBi_y□_2xTiO₃ were studied. Two regions of the phase diagram are studied: one having constant composition of bismuth and the other of lithium. The amount of inserted lithium depends on both the number of vacancies and the amount of bismuth in the original samples. The conductivity of the samples is directly related to the amount of inserted lithium and the activation energy depends on the unit cell volume. An analysis of the electronic and ionic components of the conductivity reveals that the untreated materials are pure ionic conductors, while after Li-insertion an additional electronic conductivity (t < 10^-2) occurs, due to a polaron mechanism, with an activation energy of 0.8 eV.