Two New Non-centrosymmetric n = 3 Layered Dion–Jacobson Perovskites: Polar RbBi₂Ti₂NbO₁₀ and Nonpolar CsBi₂Ti₂TaO₁₀

Abstract

Single crystals of CsBi2Ti2TaO10 (I) are prepared by solid state reaction of Cs2CO3, Bi2O3, TiO2, and Ta2O5 (Pt crucible, 1000 °C, 24 h, 30% yield).

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

“… 49 In common with many n = 3 layered perovskite-related materials, the B cations in the outer layers of the perovskite blocks in Cs Ln 2 Ti 2 NbO 10 are displaced out-of-center toward the interblock layers, giving shorter B –O apical bond lengths, as reported previously for CsBi 2 Ti 2 NbO 10 20 and for n = 3 Aurivillius phases such as Bi 2 Sr 1.4 La 0.6 Nb 2 MnO 12 , 55 Bi 2 Sr 2 Nb 2.5 Fe 0.5 O 12 , 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 Cs Ln 2 Ti 2 NbO 10 ( Ln = La, Nd). We will consider first the average structures for Cs Ln 2 Ti 2 NbO 10 ( Ln = La, Nd) and distortions that give rise to lower symmetry (polar) regions at shorter length scales, as well as the factors that give rise to the differing origins of polar behavior.…”

“…The long-range, average structures described above for Cs Ln 2 Ti 2 NbO 10 ( Ln = La, Nd) share similarities with those reported for A′ Bi 2 Ti 2 NbO 10 ( A′ = Cs, Rb), 20 , 23 with the same B -site cation ordering and similar out-of-center displacements for these ions. For Cs Ln 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).…”

“… 20 Experimental studies of RbBi 2 Ti 2 NbO 10 and CsBi 2 Ti 2 TaO 10 suggest these closely related materials behave analogously. 23 However, the possibility of tuning between proper and hybrid-improper mechanisms and the role of A cations in these systems has not been explored.…”

Ferroelectric Sr3Zr2O7: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

“…Here, we demonstrate that ferroelectricity emerges by layering nonpolar perovskite SrZrO 3 with nonpolar rock salt‐structured SrO to form the n = 2 Ruddlesden–Popper (RP) A 3 B 2 O 7 structure . We show that Sr 3 Zr 2 O 7 is a hybrid improper ferroelectric (HIF), whereby ferroelectricity with an electric polarization P occurs from a combination of two nonpolar lattice modes, Q 1 and Q 2 , interacting through a trilinear term of the form PQ 1 Q 2 . The role played by the two nonpolar structural distortions—oxygen octahedral rotations (OOR, out‐of‐plane rotational modes) and oxygen octahedral tilts (OOT, in‐plane rotational modes)—in stabilizing ferroelectricity is determined using a combination of synchrotron X‐ray diffraction (SXRD), neutron powder diffraction (NPD), optical second harmonic generation (SHG), and first‐principles density functional theory (DFT) calculations.…”

Solid‐state nuclear magnetic resonance of spin‐9/2 nuclei 115In and 209Bi in functional inorganic complex oxides

“…[26,27] The stereochemically active lone pair in Bi 3+ can lead to noncentrosymmetric structures with useful optoelectronic and ferroic properties. [28][29][30][31][32] Given the range of technological applications and frequently cation-mixed and/or poorly diffracting nature of bismuth and indium oxides, it is desirable to develop alternative metrologies to study their atomic environments. 115 In and 209 Bi solid-state nuclear magnetic resonance (NMR) spectroscopy could, in principle, offer additional insights into the local coordination, symmetry, and ionic/polyhedral dynamics.…”