Coulometric titration solid electrolytes

A solid state galvanic cell consists of electrodes and the electrolyte. Solid electrolytes are available for many different mobile ions (see Section 15.3). Their ionic conductivities compare with those of liquid electrolytes (see Fig. 15-8). Under load, galvanic cells transport a known amount of component from one electrode to the other. Therefore, we can predetermine the kinetic boundary condition for transport into a solid (i.e., the electrode). By using a reference electrode we can simultaneously determine the component activity. The combination of component transfer and potential determination is called coulometric titration. It is a most useful method for the thermodynamic and kinetic investigation of compounds with narrow homogeneity ranges. For example, it has been possible to measure in a... 

The measurements of metaUurgically prepared alloys, which were used as alloy electrodes in cells as in Figure 3.7, are limited in their number of data points. A big advantage that was introduced by Wagner is the coulometric titration. The cell is either a two-electrode cell or a three-electrode cell with a solid electrolyte or a molten salt electrolyte. The alloy is not preformed but is formed instead by a slow electrochemical deposition of component A into the component B (current 1). The mole number of A deposited is determined by the equation... 

Gas Titration with Solid Electrolytes, Fig. 3 Schematic drawing of a coulometric SE sensor based rai batch-lite oxygrai titration into a closed chamber [9]... 

Oxygen solid electrolyte coulometry in quasi-closed systems is understood at first the complete isolation of the material to be investigated in a minimal chamber with gas-dense solid electrolyte wall attached out- and inside with electrochemical active electrodes. Then oxygen can only be admitted to the chamber or removed from it quantitatively by coulometric titration. The chamber can be made completely (Fig. 2) or partly of solid electrolyte material. Current (lei) and potential (Uei) electrodes are insulated from each other with gas-dense high temperature glass (HTG) layer, so titration current and voltage are simultaneously measurable at this construction of the cell. 

In the case of diffusion of foreign atoms in small concentrations into a host lattice, e. g., a solid or liquid metal, this situation is simplified because of the applicability of the laws of ideal diluted solid solutions. The concentration of the electroactive species at the interface with the electrolyte is given directly by Nemst s law. In case of nonideal behavior, further information concerning the activity-concentiation relation of the diffusing species is necessary. This may be acquired from coulometric titration measurements. 

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