Single-Phase Solid Electrolytes

FIGURE 1.5 The aging of the solid electrolyte Zr(Y)Oi909 at the consecutive temperature changes. 

One of the reasons of aging in the single-phase electrolytes is the development of the ordering structure in the cation sublattice of the solid solution [30]. However, it is impossible to use ordinary XRD methods for investigating these ordering structures owing to the same value of the X-ray dissipation factor for Zf and Y +. 

Another possible reason of aging in such solid electrolytes can be the appearance and growth of the microdomains of a small size possessing equal to the lattice value. These microdomains of size 5-30 nm have been discovered by the electron-graphical method in the system Zr02-CaO [38, 39], However, no direct experimental data have been reported so far about their existence in the solid solutions Zr02-R203. 

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Because of the interest in its use in elevated-temperature molten salt electrolyte batteries, one of the first binary alloy systems studied in detail was the lithium-aluminium system. As shown in Fig. 1, the potential-composition behavior shows a long plateau between the lithium-saturated terminal solid solution and the intermediate P phase "LiAl", and a shorter one between the composition limits of the P and y phases, as well as composition-dependent values in the single-phase regions [35], This is as expected for a binary system with complete equilibrium. The potential of the first plateau varies linearly with temperature, as shown in Fig. 2. 

The purpose of this chapter is to outline the simplest methods of arriving at a description of the distribution of species in mixtures of liquids, gases and solids. Homogeneous equilibrium deals with single phase systems, such as electrolyte solutions (e.g., seawater) or gas mixtures (e.g., a volcanic gas). Heterogeneous equilibrium involves coexisting gaseous, liquid and solid phases. 

It is a misinterpretation of the concept of a phase to consider these two possible sites for a counterion as separate phases. This confuses a macroscopic property of a well-defined phase (a solid) in equilibrium with another well-defined phase (a homogeneous electrolyte solution) with an internal property of an inhomogeneous single phase, the macroionic (or colloidal or gel) phase. It divides the macroionic phase into two regions that have no physical counterpart. 

Figure 8. Reactor assembly and fiimace used with the single-pellet configuration. 1 glass tube volume SO-i 00 mL. 2 electrochemical cell. WE working electrode CE counter electrode RE reference electrode SE solid electrolyte. Reprinted from / Electroanal. Chem., G. F6ti, V. Stankovid, I. Boizonella, and Ch. Comninellis, Transient Behavior of Electrochemical Promotion of as-Phase Catalytic Reactions, (2002) in press, with permission from Elsevier Science.

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