Ionic superlattices

Pig. 5.99 Ionic superlattices of CaP2 and BaFa show significant enhancement of the F conductivity which progressively increases with the density of interfaces [283]. The period L/N is varied from nm to /im while the total thickness L is approximately constant. The temperature and thickness dependence is initially as predicted by semiinfinite space charge theory. The o-increase does not saturate in the sub-Debye regime, it rather increases more steeply. At extremely small spacings (cf. insert) the conductivity drops with decreasing L due to loss of connectivity. 

Tolstoi, V. P Tolstobrov, E. V. 1994. Cu02/Ba02 superlattices grown by ionic layering. Inorg. Mater. 30 875-878. 

Pang G., Feng S., Tang Y., Tan C. and Xu R., Hydrothermal synthesis, characterization, and ionic conductivity of vanadium-stabilized Bii7V3033 with fluorite-related superlattice structure, Chem. Mater 10 (1998) pp. 2446-2449. 

The ionic conductivity of YSZ can be also enhanced by the introduction of high density of dislocations [17] or interfaces that act as rapid diffusion paths for oxygen vacancies. Such an idea has been discussed for BaF2/CaF2/Bap2 superlattices where a substantial increase of ionic conductivity was observed [18]. In this system a progressive increase in the conductivity was correlated with the increase of interfacial density. 

Most 3d nanoparticle superlattices have a close-packed twofold coordination. Namre forms crystal lattices of lower coordinations in a great variety of ionic crystals. Recently Kalsin et al. (78) assembled an ionic lattice of oppositely charged nanoparticles. The nanoparticles were gold ligated with mercaptoundecanoic acid and silver ligated with A(,A(,A(-trimethyl(l 1-mercaptoundecyl) ammonium chloride salt. The nanoparticles were essentially the same size, each about 5 nm in diameter. 

Discotic molecules with a benzene-1,3,5-tricaboxyamide (BTA) core are used to form a columnar LC phase through threefold intermolecular H-bonding. The BTAs are functionalized with a carboxylic acid moiety, which is able to form an ionic interaction with amines. A well-ordered superlattice is formed by mixing the BTAs... 

Physically the simplest, though certainly not the easiest, of the electrostatic problems is the response of a system to constant external electric field. In general, there is no principal objection to incorporating one more potential "external to the SYstM of electrons" into the HKS equations the ionic potential V ° (r) can readily be replaced by some V ° (r) + V (r), where V is the potential of he field external to the crystal. The difficutly arises when V is to represent a macroscopic field constant in space it comes from the impossibility for plane-wave expansions to handle any quantity which does not have the periodicity of the lattice or superlattice. The problem was met already in Sections 6 and 4.3.10, and it is not new in solid state physics. The standard solution used in other contexts, viz. evaluating the q > 0 limit, is not practical in the "direct" approach, because the smallest q s which can be handled are likely to be still too large for evaluating the q > 0 limit numerically. 

Korte C, Peters A, Janek J, Hesse D, Zakharov N (2008) Ionic conductivity and activation energy for oxygen ion transport in superlattices - the semicoherent multilayer system YSZ (Zr02 -t 9.5 mol% Y203)1 203- Phys Chem Chem Phys 10(31) 4623 635... 

In the previous sections blends were considered in which entro-pic forces originating from different stretchings of chemically similar blocks controlled the formation of common superlattices. Besides entropic contributions, enthalpic interactions can also play a dominating role in block copolymer blending, for the same reasons as in the case of blends of homo or random copolymers. For example, hydrogen bonding or ionic interactions can force the formation of common super lattices, if, for example, a polyadd block of one block copolymer is mixed with the polybase block of another block copolymer. In such... 

A. Peters et al., Ionic conductivity and activation energy for oxygen ion transport in superlattices—The multilayer system CSZ (Z1O2 + CaO) / AI2O3. Solid State Ionics 178, 67-76 (2007)... 

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