Structural and magnetic characterisation of Aurivillius material Bi2Sr2Nb2.5Fe0.5O12

Proper Ferroelectricity in the Dion–Jacobson Material CsBi2Ti2NbO10: Experiment and Theory

“…This is in agreement with our DFT results and with results from recent first-principles calculations which show significant polar displacement of B site cations in n = 2 DJ phases, which provides the major contribution to the polarization in these materials . This is in contrast to most other families of layered perovskite-related materials and might explain the difficulties in introducing magnetic d n ions onto the DJ B sites, in contrast to other systems such as the Aurivillius materials. ,− …”

Synthesis, structure and characterisation of the n=4 Aurivillius phase Bi5Ti3CrO15

“…7, the Bi cations in the perovskite-type layer of Table 2 appears typical of Aurivillius phases with cation disorder on both A-and B-sites of the perovskite type layer (see e.g. [20] and [40]). The larger thermal parameters may relate to small static displacements of these atoms from the refined positions, influenced by cation disorder.…”

“…The final combined agreement indices were w 2 ¼4.09, R wp ¼9.92, and R p ¼9. 20. Refinement of a model in space group Amam, which permits the same co-operative octahedral tilt pattern as A2 1 am but without polar displacements, yielded physically unrealistic thermal parameters for several atoms and so was rejected.…”

“…The higher homologues Bi 6 Fe 2 Ti 3 O 18 (n ¼5) and Bi 9 Fe 5 Ti 3 O 27 (n¼ 8) are also reported to show co-existence of ferroelectric and antiferromagnetic ordering, but have not been investigated in detail [17,18]. Several recent studies have demonstrated the potential for doping n¼3 Aurivillius phases with transition metal 5 ), exhibited almost ideal Curie-Weiss paramagnetism with short range antiferromagnetic exchange; both compounds adopt the non-polar aristotype I4/mmm structure [19,20]. Sharma et al reported ferroelectric behaviour in a family of transition metal substituted Aurivillius phases, formulated Bi 2 À x S r2 + x (Nb,Ta) 2 + x M 1 À x O 12 with M ¼Ru 4 + (4d 4 ), Ir 4 + (5d 5 ), Mn 4 + (3d 3 ) and xE0.5; these compounds are paramagnetic with short range ferromagnetic (Mn) or antiferromagnetic (Ru, Ir) exchange [21,22].…”

Tuning between Proper and Hybrid-Improper Mechanisms for Polar Behavior in CsLn2Ti2NbO10 Dion-Jacobson Phases

“…For CsLn 2 Ti 2 NbO 10 , Ti 4+ preferentially occupies the smaller and higher-symmetry central B(1) site, consistent with its size (six-coordinate ionic radii of 0.605 and 0.64 Å for Ti 4+ and Nb 5+ , respectively). 49 In common with many n = 3 layered perovskite-related materials, the B cations in the outer layers of the perovskite blocks in CsLn 2 56 and Bi 4 Ti 3 O 12 . 19 However, the noncentrosymmetric, polar structures reported for A′Bi 2 Ti 2 NbO 10 (A′ = Cs, Rb) 20,23 differ from the results of NPD analysis described here for CsLn 2 Ti 2 NbO 10 (Ln = La, Nd).…”