The role of Tb-doping on the structural and functional properties of Bi4−xTbxTi3O12 ferroelectric phases with the Aurivillius type structure

Abstract

Synthesis, crystal structure, dielectric, and magnetic properties of the Aurivillius phase Bi 4-x Tb x Ti 3-O 12 (x = 0.0, 0.4, 0.6, 0.8) are reported. The samples were synthesized using standard solid state reaction technique. The thermal stability of the obtained solid solutions was investigated. For x B 0.8, the samples crystallized in an orthorhombic symmetry. All the samples showed finite second harmonic generation response indicating a noncentrosymmetric structure. The structural data could be refined using the polar orthorhombic space group B2cb. The orthorhombicity decreases with an increase in the Tb 3? concentration. The orthorhombic distortions in these compositions are related to the Bi 3?-based perovskite sublattice. Our results indicate that the non-lone pair Tb 3? cations preferentially occupy the perovskite sublattice initially, but with an increase in the doping concentration they can partially substitute the Bi 3? ions in the fluorite block. Temperature dependent dielectric measurements revealed a decrease in the ferroelectric Curie temperature T C with an increase in x from T C = 904 K (for x = 0) to 877 K (for x = 0.4). Further increase in x led to a cross-over to a relaxor-type behavior. Magnetic measurements showed that the samples are paramagnetic down to 5 K.