Properties of Bi₄Ti₃O₁₂–(Na_1/2Bi_1/2)TiO₃ Piezoelectric Ceramics

Ceramics of the series (1-x)Bi₄Ti₃O₁₂-x(Na_1/2Bi_1/2)TiO₃ (BTO-NBT) were made using a conventional mixed oxide and carbonate process. The structural properties revealed that the system passes through the formation of Aurivillius compounds with increasing number of perovskite blocks for an increasing amount of NBT up to a maximum of four. Regions of coexistence of two layered compounds are also present. A perovskite phase starts to appear, as NBT, at 40%mol BTO. Even at low concentrations (5% BTO) a four layer Aurivillius phase formed together with the perovskite structure. X-ray diffraction (XRD) analysis at low angles (2θ<20°) proved to be a powerful tool for the identification and characterization of the layered structures. dc resistivity was measured for the composition corresponding to pure phases of the series in the range 15–65°C. The data obtained were interpreted on the basis of the structures of the Aurivillius compounds.