Silver chalcogenide

Alternatively, it is possible to install fibre optic probes directly in the main stream in-line while the IR spectrophotometer remains remotely in a low vibration laboratory environment. In-line analysers, which do not remove any sample from the line, have the minimum possible lag time and do not change the sample physically or chemically from its nature in the process. Recently, bundles of 500 /xm optic fibres have been developed for the 5000-900 cm (2000-11,000 nm region), which permit transmission of IR energy over distances of several metres. Lowry et al. [76] have evaluated fibre-optic cables that might prove useful in FTIR remote sampling applications. The various optical fibres (chalcogenide, silver halide, heavy metal fluoride or sapphire) differ in their spectral window [77]. Due to the thermal stability and the spectral window, sapphire fibres are considered suitable for in-line characterisation of polymer melts in a production line (e.g. in an extruder head) as an alternative to discontinu-ously operating conventional off-line transmission IR spectroscopy of polymer films [78]. 

Some MIECs exhibit metallic properties. These materials can have different concentration of the mobife ioiflc species, compared with that of electrons and holes. Silver chalcogenides, Ag2+sX (X = S, Se, or Te) is an example of a metallic MIEC that conduct electrons and silver ions. These materials are good electronic conductors (close to metallic) and show interesting electronic behavior as a function of temperature as... 

CsFeo.72Agi.28Te2,1053 and Cs2Ag2ZrTe4. The latter has a structure that comprises 2D slabs of Ag- and Zr-centered tetrahedral separated by Cs+ cations.1054 Gas-phase silver chalcogenide ions of the type [Ag2 i E ] (E = S, Se, Te) with < 14 have been investigated by laser-ablation Fourier transform ion cyclotron resonance mass spectrometry.1055... 

Lead-calcium-silver anodes, 74 777 Lead-calcium-tin alloys, 74 775-776 Lead carbonates, 74 794-795 Lead chalcogenides, 79 157 Lead chloride, 74 785 Lead chromate... 

The group of ion-selective electrodes with fixed ion-exchange sites includes systems with various membrane structures. The membranes are either homogeneous (single crystals, pressed pellets, sintered materials) or heterogeneous, set in an inactive skeleton of various polymeric materials. Important electrode materials include silver halides, silver and divalent metal chalcogenides, lanthanum trifluoride and various glassy materials. Here, the latter will be surveyed only briefly, for the sake of completeness. 

A table of ionic conductors that behave in a similar way to a-Agl is given in Table 5.4. Some of these structures are based on a close-packed array of anions and this is noted in the table the conducting mechanism in these compounds is similar to that in a-Agl. The chalcogenide structures, such as silver sulfide and selenide, tend to demonstrate electronic conductivity as well as ionic, although this can be quite useful in an electrode material as opposed to an electrolyte. 

The solubility products of most halides are much higher in general than those of chalcogenides. Those of the silver halides are fairly low, which allows these depositions to take place readily. 

Although CD seems to have been limited to chalcogenides (including oxides and hydroxides) and isolated cases of carbonates, silver halides, and elemental Se, it should be possible to deposit salts of other anions. There are a number of other anions that can be slowly and homogeneously generated. These are discussed in Chapter 3. 

In contrast, in most ion-selective membranes the charge conduction is done by ions. Thus, a mismatch between the charge-transfer carriers can exist at the noble metal/membrane interface. This is particularly true for polymer-based membranes, which are invariably ionic conductors. On the other hand, solid-state membranes that exhibit mixed ionic and electronic conductivity such as chalcogenide glasses, perovskites, and silver halides and conducting polymers (Lewenstam and Hulanicky, 1990) form good contact with noble metals. 

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