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.

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