Slicing the Perovskite Structure into Layers: Synthesis of Novel Three-Dimensional and Layered Perovskite Oxides, ALaSrNb2MIIO9 (A = Na, Cs)

Abstract

NaLaSrNb2Co09 brown 3.967(5) NaLaSrNb2Ni09 gray 3.966(3) NaLaSrNb2Cu09 brown 3.978(5) NaLaSrNb2Zn09 white 3.988(4) CsLaSrNb2Cu09 gray 7.846(5) CsLaSrNb2Zn09 white 7.837 (8) 3-D perovskite 4.00 3-D perovskite 2.96 3-D perovskite 1.70 3-D perovskite 30.49(2) 2-D perovskite 1.68 30.66(3) 2-D perovskiteThe oxides possessing perovskite (CaTi03)-related structures are indeed legion.* 1 Besides the stoichiometric (ABO3) perovskites and their ordered variants (e.g., A2BB'06, AsBB^Oci), quite a few defective perovskites (e.g., ABO3-*) forming a variety of perovskite superstructures are known.2 Furthermore, a number of layered oxides, such as the Ruddlesden-Popper phases3 and the Aurivillius phases,4 which could be regarded as derivatives of the perovskite structure, are also known. These materials contain two-dimensional (2-D) perovskite slabs of composition [A"-iB"03"+i] as one of the units building the layered structure. The A"-iBn03"+i units may be thought of as derived by slicing, as it were, the three-dimensional (3-D) perovskite structure along one of the three cubic directions.5Considering the large number of perovskite-related oxides known at present,1 one would feel that all the possible combinations of elements that would give perovskite-related oxides have already been exhausted. Fortunately, this is not so, because time and again, novel members are being added to the growing list of perovskite-related phases. A typical example is the discovery of superconducting YBa2Cu307, which possesses a unique vacancy-ordered perovskite structure.6As a part of our continuing efforts to synthesize novel layered oxides exhibiting interlayer chemistry,7 we investigated the formation of perovskite-related phases for the compositions ALaSrNb2Mn09 (A = alkali metal and M = Co, Ni, Cu, or Zn). To our surprise, the compositions adopted a cubic (3-D) perovskite structure when A = Na and a layered (2-D) perovskite structure, related to CsCa2Nb30io,8 when A = Cs. This result, which is reported in this communication, reveals the interesting possibility of tailoring perovskite (ABO3) oxides into 2-D or 3-D structures by the appropriate choice of A-site cations. Furthermore, the strategy can be extended to synthesize layered perovskite oxides of variable thickness by choosing appropriate chemical compositions. We believe that the present f Contribution No. 1075 from the Solid State and Structural Chemistry Unit.

Photocatalytic properties of a novel layered photocatalyst CsLaSrNb2NiO9

“…In accordance with the previous paper [7], CsLaSrNb 2 NiO 9 crystallized in a layered perovskite structure similar to that of CsCa 2 Nb 3 O 10 . The color of the prepared CsLaSrNb 2 NiO 9 powders is gray.…”

“…As shown in figure 3, [9]. Different with NaLaSrNb 2 NiO 9 oxides that crystallizing in a 3-D perovskite, the CsLaSrNb 2-NiO 9 was crystallized in a 2-D layered perovskite structure because of the large tolerance factor [7]. It is reported that the layered perovskite CsLaSrNb 2 NiO 9 consists of perovskite-like slabs of composition [LaSrNb 2 NiO 9 ] interleaved by the large Cs cations.…”

“…It is reported that the layered perovskite CsLaSrNb 2 NiO 9 consists of perovskite-like slabs of composition [LaSrNb 2 NiO 9 ] interleaved by the large Cs cations. The Nb and Ni metal ions occupy the octahedral sites at random with some oxygen vacancies in ordered or disordered distributing around [7]. Previous studies of Ni-doping on the photocatalytic properties of TiO 2 and SrTiO 3 showed that an occupied level was created in the center of the band gap due to the Ni 3d band splitting in the oxides [10], indicating the important role of Ni 3d band in deciding the visible-light-induced photocatalytic activities.…”

“…The CsLaSrNb 2 NiO 9 was prepared according to the literature: [7] the stoichiometric mixtures of the starting oxides were ground and mixed thoroughly in an agate mortar. An excess amount of Cs 2 CO 3 (40 mol%) was added to compensate for the loss due to the volatilization of the cesium component.…”

Photocatalytic degradation of organic dyes under visible light irradiation by floral-like LaFeO3nanostructures comprised of nanosheet petals

“…Thus, from the scientific and technological point of view developing convenient and effective pathways for the synthesis of surfactant assisted nanostructures is of special significance. 21,22 It has been reported by Fujishima and Honda that the photocatalytic reaction has the potential to eliminate pollutants. Subsequently, extensive research efforts have been devoted towards environment and energy challenges.…”