Na₂Ln₂Ti_3-xMn_xO₁₀ (Ln = Sm, Eu, Gd, and Dy; 0 ⩽ x ⩽ 1):  A New Series of Ion-Exchangeable Layered Perovskites Containing B-Site Manganese

Abstract

Na 2 Ln 2 Ti 3-x Mn x O 10 (Ln ) Sm, Eu, Gd, and Dy; 0 e x e 1), a new series of triple-layer Ruddlesden-Popper phases, were synthesized by direct solid-state reaction. The smaller lanthanides enhance manganese solubility in the parent titanate, and an optimized synthetic approach allows Na 2 Ln 2 Ti 3-x Mn x O 10 to be stabilized relative to competing single-layer and cubic phases. The X-ray diffraction patterns of Na 2 Ln 2 Ti 3-x Mn x O 10 can be indexed on a tetragonal unit cell with a doubled a axis. The Na 2 Ln 2 Ti 3-x Mn x O 10 phases undergo ion exchange, forming A 2 Ln 2 Ti 3-x Mn x O 10 (A ) Li, NH 4 ) by exchange in the molten nitrates. Na 2 Ln 2 Ti 3-x Mn x O 10 is also amenable to divalent ion exchange, evidenced by the formation of A II Gd 2 Ti 2 MnO 10 (A II ) Mg, Ca) by ion exchange in aqueous MgCl 2 and Ca(NO 3 ) 2 , respectively. Temperature-dependent magnetic susceptibility measurements indicate that the Na 2 Ln 2 Ti 3-x Mn x O 10 phases are paramagnetic and suggest the onset of weak magnetic ordering at low temperatures (<10 K).

Perovskites by Design: A Toolbox of Solid-State Reactions

“…Ruddlesden−Popper phases 18,19 (Figure c) also undergo ion-exchange reactions. Like the Dion−Jacobson phases, the interlayer alkali cations of Ruddlesden−Popper phases (typically Na + , K + , and sometimes Rb + ) can be replaced by smaller alkali cations such as Na + , Li + , NH 4 + , and Ag + using molten salt ion-exchange reactions (Figure b). ,,, Ruddlesden−Popper phases are especially amenable to divalent ion exchange because two interlayer alkali cations can be replaced with one divalent cation to form a Dion−Jacobson phase (Figure a). Hyeon and Byeon prepared M II La 2 Ti 3 O 10 (M = Co, Cu, Zn) by exchanging 2Na + for M 2+ using the molten nitrates, chlorides, or eutectic mixtures …”

“…By introducing d n ( n > 0) cations into the B-sites of ion-exchangeable layered perovskites, it may be possible to design new electronic or magnetic materials that have ordered sequences of A- and/or B-site cations. Electronically active B-site cations could be incorporated directly into the parent Ruddlesden−Popper phase, as in Na 2 La 2 Ti 3 - x Ru x O 10 and Na 2 Ln 2 Ti 3 - x Mn x O 10 (Ln = Sm, Eu, Gd, Dy), or by topochemical methods such as the reductive intercalation of a Dion−Jacobson phase, as in the synthesis of Rb 2 LaNb 2 O 7 from RbLaNb 2 O 7 , By starting with Aurivillius phases, it may be possible to expand the choice of interesting electronic or magnetic cations in designing new perovskites that yield interesting properties.…”

“…Using this approach, it is possible to precisely define the number of defect sites in the product perovskite simply by adjusting the ratio of Eu: La in the layered precursor and the amount of Ca 2+ that is exchanged for Na + in the ion-exchange step. By applying this approach to layered perovskite precursors that contain reducible B-site cations, such as Na 2 La 2 -Ti 3-x Ru x O 10 94 and Na 2 Ln 2 Ti 3-x Mn x O 10 , 50 it may be possible to fine-tune the oxidation state of Ru or Mn in the product perovskite phase by using substoichiometric ion exchange followed by combined topochemical dehydration and reduction. Work along these lines is currently in progress.…”

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

“…As one of the most versatile classes of materials, perovskites have been continuously attracted by materials scientists owing to their fascinating characteristics such as magnetic, superconductive, dielectric, thermoelectric, electrocatalytic, ferroelectric, and optical properties. − Specific families of the perovskites with layered structures are generally classified as Ruddlesden–Popper (RP; A′ 2 [A n –1 B n O 3 n +1 ]), − Aurivillius ((Bi 2 O 2 )­[A n –1 B n O 3 n +1 ]), − and Dion–Jacobson (DJ; A′[A n –1 B n O 3 n +1 ]) phases. − While each of the different layered perovskites shares common two-dimensional anionic slabs ([A n –1 B n O 3 n +1 ]), the motifs separating the layers (A′ or Bi 2 O 2 ) and the subsequent offsetting of the layers are dissimilar. Many interesting aforementioned characteristics found from bulk ABO 3 perovskites have been also similarly observed from layered perovskites. − Interestingly, however, while the greater part of the known ABO 3 perovskites crystallized in centrosymmetric (CS) space groups, a number of layered perovskites were found to crystallize in non-centrosymmetric (NCS) polar structures. − Several representative NCS polar layered perovskites are Ca 3 Ti 2 O 7 (RP), Bi 4 Ti 3 O 12 (Aurivillius), , and CsBiNb 2 O 7 (DJ). ,, Since very enchanting properties such as pyroelectricity and ferroelectricity may be expected from polar materials, layered perovskites with polar symmetry must be one of the most promising materials for thermal detectors, pollution monitors, and random-access memories.…”

Synthesis and Photoluminescence Properties of a Novel Red-Emitting Na2Y2Ti3O10:Eu3+,Sm3+ Phosphor for White-Light-Emitting Diodes

“…This material belongs to the Na 2 Ln 2 Ti 3 O 10 (Ln = lanthanide ions) group containing triple perovskite layers. Such materials have been studied for use as photocatalysts, ion-exchangeable materials, and phosphors. − Na 2 Y 2 Ti 3 O 10 itself is a novel composition. The photoluminescence (PL) properties of the Na 2 Y 2 Ti 3 O 10 :Eu 3+ phosphor and the effects of codoping with the Sm 3+ ion on the PL properties were investigated in detail.…”