Solid stability range

The dotted lines represent the cases when the above cathodic reactions, (a) or (b), drive the reaction. The solid lines indicate the stability ranges for Fe and its corrosion products (Fe, Fe, Fe O, Fc202, tthcOT). 

The third aspect, the stability range of solid electrolytes, is of special concern for alkaline-ion conductors since only a few compounds show thermodynamic stability with, e.g., elemental lithium. Designing solid electrolytes by considering thermodynamic stability did lead to very interesting compounds and the discovery of promising new solid electrolytes such as the lithium nitride halides [27]. However, since solid-state reactions may proceed very slowly at low temperature, metasta-... 

Today, the term solid electrolyte or fast ionic conductor or, sometimes, superionic conductor is used to describe solid materials whose conductivity is wholly due to ionic displacement. Mixed conductors exhibit both ionic and electronic conductivity. Solid electrolytes range from hard, refractory materials, such as 8 mol% Y2C>3-stabilized Zr02(YSZ) or sodium fT-AbCb (NaAluOn), to soft proton-exchange polymeric membranes such as Du Pont s Nafion and include compounds that are stoichiometric (Agl), non-stoichiometric (sodium J3"-A12C>3) or doped (YSZ). The preparation, properties, and some applications of solid electrolytes have been discussed in a number of books2 5 and reviews.6,7 The main commercial application of solid electrolytes is in gas sensors.8,9 Another emerging application is in solid oxide fuel cells.4,5,1, n... 

Valyashko and Gode (414) have summarized the conditions necessary for formation of borates of sodium, potassium, ammonium, calcium, and magnesium. The effect of varying the cation is to alter the type of borate that is stable in contact with the aqueous solution. The stability ranges for solid phases in the sodium and calcium systems are shown in Table V. 

The pH ranges over which the solid phases are stable agree reasonably well with the stability ranges of the polyborate ions BsOsCOH) , B4Os(OH)4, B3Oa(OH)i outlined in Section IV,A thus it can be expected that to precipitate a borate of a particular structure, it should be prepared from a solution containing those same borate ions. 

A great variety of formulas for this phase can be found, e.g. 48 s°). Some of these data are dubious, others are only correct in respect of the temperature-dependent solid solution range of the Y-phase. However, the Y-phase should be described as a compound with a Fe Mo ratio of 1 4, as this represents the only formula valid for the temperature stability range from slightly below 800 °C up to its melting point. The Y-phase can only be synthesized above 535 15 °C46 it is quench-able and probably remains metastable at room temperature. 

In many cases data are given for one substance in several states (for instance several solid states, liquid or gaseous states). For each state a new entry is made. Usually data are given for the minimum and the maximum of the stability range. 

Figs. 6A and B illustrate the plots of the functions G and H versus temperature (energy/temperature diagrams) for each polymorph and for the liquid. The thermodynamic reversibility of the solid transition between two crystalline forms is characteristic of enantiotropic systems. Each form has its thermodynamic stability range. The lower melting form is... 

Pressure is a fundamental state variable like temperature or composition and is, thus, a suitable means to modify the properties of solids. Its application induces a continuous shortening of interatomic distances, within the stability ranges of structural phases. Different types of chemical bonding will generally exhibit dissimilar changes upon application of pressure, resulting in different compressibility for covalent and metallic solids (Figure 15.7), for example. 

As far as thermodynamics is concerned, much attention has been paid to the M3LnCl6 stoichiometric compounds that exist in most of the LnCls-MCl systems and have a more extended stability range than those of a different stoichiometry. Gaune-Escard and Rycerz (2003) determined the temperatures and enthalpies of the solid-solid phase transition, as well as of fusion of MsLnCle compounds (Ln = La, Ce, Pr, Nd, Tb M = K, Rb, Cs). They are presented in Table 2.7, together with the data of the enthalpy of formation taken from the literature. 

The phase diagram iron-selenium was assessed by Okamoto [91 OKA] and it is shown in Figure V-21. The system contains several solid solution phases with stability ranges delimited by temperature. The naming of the phases is confusing and has varied over the years. The names used in [91 OKA] are adopted by the review. 

In the case of dispersions (from Latin dispergere = fine distribution) a solid phase has dispersed into the liquid phase (water as dispersing agent) owing to the polymer particles in diameter ranges of 10-4—10-5 cm (ten-thousandth to hundred-thousandth cm). The smallness of the particles and special additives (stabilizers, emulsifiers) prevent them from deposition. The solid content ranges between 40-70%. The setting mechanism for the formation of the adhesive layer is initiated by the removal of the liquid phase. This may occur by... 

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