La3+ substitution in four-layers Aurivillius phase SrBi4Ti4O15

Ceramics with the nominal composition of SrBi4−xLaxTi4O15 have been prepared within the range of 0≤x≤1.8, and the dielectric properties are investigated. Single phase SrBi4−xLaxTi4O15 solid solution exists until the secondary phase of La2/3TiO3 appears at x=1.6. The Curie temperature is 520 °C for pure SrBi4Ti4O15, and it shifts to low temperature with increasing x, which is due to the smaller structural distortion caused by La3+ substitution. In addition, the dielectric constant anomaly is suppressed with the substitution. No dielectric relaxation behavior is observed. When x≥1.2, the paraelectric state is attained in the present ceramics. La3+ substitution effects on the SrBi4Ti4O15 ceramics are also compared with the previous work on Bi4−xLaxTi3O12.