Dopant inclusion

Dopant inclusion by co-crystallisation and vapour phase doping during polymerization have also been investigated (140). Conductivities as high as lO S/cm have been observed, but despite the apparently unperturbed crystal quality the conductivities of the doped samples were essentially isotropic. It should be noted that TS crystals grown in air contain considerable quantities of O2, this does not seem to affect their conductivity but is capable of oxidation of the polymer chain immediately after photo-excitation of charge transfer between the polymer backbone and the 2 (141). 

Inherently Conducting Polymers. Conducting polymers are polymers with a pi-electron backbone capable of passing an electrical current. These polymers generally are not sufficiently conductive as neat polymers but require the inclusion of an oxidi2ing or reducing agent (dopant) to render them conductive. 

Extrinsic Defects Extrinsic defects occur when an impurity atom or ion is incorporated into the lattice either by substitution onto the normal lattice site or by insertion into interstitial positions. Where the impurity is aliovalent with the host sublattice, a compensating charge must be found within the lattice to pre-serve elec-troneutality. For example, inclusion of Ca in the NaCl crystal lattice results in the creation of an equal number of cation vacancies. These defects therefore alter the composition of the solid. In many systems the concentration of the dopant ion can vary enormously and can be used to tailor specific properties. These systems are termed solid solutions and are discussed in more detail in Section 25.1.2. 

The spin transition could be monitored by ESR in Mn(II) or Cu(II)-doped materials. The related pure compounds of the dopants are strictly isomor-phous with [Fe(abpt)2(TCNQ)2]. The inclusion of a small percentage of the paramagnetic Mn(II) or Cu(II) ions provides ESR probes for monitoring the Fe(II) spin transition from within the crystal lattice. The results are displayed in Fig. 11. 

The introduction of defects into the perovskite structure and their distribution in the structure are key factors that determine the protonic conductivity [50,51], The inclusion of trivalent dopants ideally takes place, as described in the Kroger-Vink notation, [43] by... 

Alternative methods for introducing electrical conductivity into diamond have been developed, which include dopants such as nitrogen[72,78,81,89], sp2 carbon inclusions in grain boundaries[75], and metal and metal cluster inclusions, and subsurface hydrogen[75]. Other forms of conductive diamond, such as surface conductive[81] or ultracrystalline diamond[78] have also been quoted in literature, suggesting that several types of chemically vapor-deposited diamond may find electrochemical applications[75],... 

In reduction of the doped oxide, part of the dopants is incorporated during the CVT growth of the metal particles in the form of silicates. Excess dopant, which remains on the tungsten crystal surfaces, is removed by subsequent leaching of the powder in HCl and HF acids, while the dopants which are internally trapped are retained. The amount of incorporated dopants, the size of the inclusions, and their chemical composition can be influenced by the reduction conditions within certain limits. About 100-150 ppm K, 60-100 ppm Al, and 200-300 ppm Si commonly remain in the acid-washed powder. 

In addition to nanostructural properties of the conducting polymer, considerable influence on actuation behavior has been demonstrated due to the choice of electrolyte. This has included properties of the solvent employed, and crucially the size of doping ions and their interaction with the conducting polymer. As mentioned above, PPy films doped with moderately small anions (e.g. CP) lead to actuation driven by anion movement. By contrast, it is generally found that the inclusion of a large dopant anion (e.g. DBS) within PPy leads to cation-driven actuation, typically when a smaller cation is employed (e.g. Na ). However, it is not always a simple matter of predicting which movement, anion or cation, will predominate for a particular electrolyte system, and for a particular type of... 

The role of inclusions sometimes is similar to that of dopants. If the drag on the grain boundary is sufficiently strong, the boundary could be pinned. Similarly, their effect on densification is not very significant. The effectiveness of inclusions is almost the same as that of dopants, in terms of G or p/G. 

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