Phase diagram of the Bi4Ti3O12-BaTiO3-(Na1/2Bi1/2)TiO3 system

The phases formed in the ternary system (Na1/2Bi1/2)TiO3- Bi4Ti3O12-BaTiO3 (NBT-BTO-BT) were studied at 11501C in air. A very accurate picture of the ternary phase diagram was obtained examining almost 90 different compositions, exploiting low-angle XRD analyses to study the layer compounds. New compounds with five perovskite blocks (m55) were discovered deep in the phase diagram. No compounds with m45 were found. It was also established that pure perovskite compounds can be obtained only at compositions very close to the NBT-BT line. The relationships between the phases is discussed and it is hypothesized that the number of perovskite blocks in the system is determined by charged sites being created by the progressive substitution of Bi31 in the A site of the perovskite blocks of BTO with the A cations of the perovskite end-member.