Development of non-stoichiometric SrBi 4+2x Ti 4 O 15+3x (−0·04 ≤ x ≤ 0·04) ceramics

The non-stoichiometric compositions of Bi layered structural SrBi₄Ti₄O₁₅ ferroelectric materials (SrBi_4+2xTi₄O_15+3x, x=−0·04, −0·02, 0, 0·02 and 0·04) are investigated as the main precursors to find the influence of Bi₂O₃ content on the characteristics of SrBi₄Ti₄O₁₅ ceramics. The effect of compositional variation on the sintering and the dielectric characteristics of SrBi₄Ti₄O₁₅ ceramics are deduced with the aid of X-ray diffraction patterns, scanning electron microscopy observation and dielectric–temperature curves. From the scanning electron microscopy observations, the SrBi_3·92Ti₄O_14·88 and SrBi_3·96Ti₄O_14·94 ceramics reveal two phased grain growth, bar typed and irregularly disc typed grains coexist; the other SrBi_4+2xTi₄O_15+3x ceramics reveal irregularly disc typed grains. From the X-ray patterns, the Bi₂Ti₂O₇ and SrTiO₃ phases are observed in the SrBi_3·92Ti₄O_14·88 and SrBi_3·96Ti₄O_14·94 ceramics. Except the SrBi_3·96Ti₄O_14·94 ceramics, the other SrBi_4+2xTi₄O_15+3x ceramics have revealed a splitting peak in the (119) plane. It is also shown that the compositional variation has apparent influences on the grain morphologies, the bulk densities, the Curie temperatures and the maximum dielectric constants of SrBi_4+2xTi₄O_15+3x ceramics.