Layer-structure family

An alternative structure that has also been widely investigated both for high temperature piezoelectric, as well as for ferroelectric memory applications is the bismuth layer structure family as shown in Figure 1.14 for SrBi2Ta209 (sbt), e.g. [8], The structure consists of perovskite layers of different thicknesses, separated by Bi20 + layers. It has been shown that when the perovskite block is an even number of octahedra thick, the symmetry imposes a restriction on the polarization direction, confining it to the a-b plane. In contrast, when the perovskite block is an odd number of octahedra thick, it is possible to develop a component of the polarization along the c axis (nearly perpendicular to the layers). This could be used in... 

Layer-structure family 28 NaNOa family (2, 2 1) 58 DSP (Ca2Sr(CH3CH2COO)6)... 

This highhght examines several new hybrid layered structures in the hetero-metallic perrhenate and vanadate families, whereby the late transition-metals are incorporated and their roles probed in the structures of layered solids. From these two families, new structural principles have emerged that not only help us understand key stractural features and correcdy forecast new compositions, but equally, have yielded many surprises (chirality, reduced phases) that show some of the most exciting chemistry is still waiting to be discovered or even imagined ... 

Clay minerals belong to a structural family of minerals known variously as sheet silicates, layer silicates, or phyllosilicates. Sheet silicates contain Si04 tetrahedra that are polymerized in two... 

From the above discussions it is clear that the amine has an important role in the formation of open-framework metal phosphates. Recent studies from this laboratory have shown that in the family of zinc phosphates, almost all the members in the hierarchy of open-framework structures can be synthesized using the same structure-directing agent, triethylenetetramine (TETA) [32], In Fig. 7.18 we show all the structures obtained with TETA along with the relative concentrations of the amine and the phosphoric acid employed in the synthesis. We see that the one-dimensional (ladder) and the two-dimensional (layer) structures are obtained when the relative concentration of phosphoric acid is high with the ratio of concentrations of the acid and the amine in the range 3 1-4 1. This is in contrast to the three-dimensional structures where the ratio... 

AB2 Systems. Since layered structures are important variants in AB2 systems (e.g. the Cdl2 and CdCb families of structures), it was deemed necessary to always use a Coulomb potential without a damping term. The method chosen to perform the full Coulomb sum was the one suggested by de Leeuw66. Again, the resulting structure candidates in general did not depend on the exact values of the effective potential. The most common structure types found are summarized in table 3. We note that these include many commonly found structures like anatas,... 

Among the inorganic open-framework compounds, the family of phosphates is a large one [3]. A large variety of open-framework metal phosphates of different architectures have been synthesized in the last few years. They include one-dimensional (ID) linear chain and ladder structures, two-dimensional (2D) layer structures and three-dimensional (3D) channel structures [4]. In the linear chain and ladder structures, four-membered metal phosphate units of the type M2P2O4 share comers and edges respectively. Zero-dimensional four-membered zinc phosphates have been synthesised and characterized recently [5]. Several open-framework metal carboxylates have also been reported [6] and the presence of a hierarchy of zinc oxalates covering the monomer, dimer, chain, honeycomb-layer and 3D structures has indeed been established [7]. 

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