Schmalzried

The enormous amount of research at the interface between physical and structural chemistry has been expertly reviewed recently by Schmalzried in a book about chemical kinetics of solids (Schmalzried 1995), dealing with matters such as morphology and reactions at evolving interfaces, oxidation specifically, internal reactions (such as internal oxidation), reactions under irradiation, etc. 

Two German physical chemists, W. Sehottky and C. Wagner, founded this branch of materials seience. The story is very clearly set out in a biographical memoir of Carl Wagner (1901 1977) by another pioneer solid-state chemist, Hermann Schmalzried (1991), and also in Wagner s own survey of point defects and their interaction (Wagner 1977) - his last publieation. Sehottky we have already briefly met in connection with the Pohl school s study of colour centres... 

Schmalzried, H. (1991) Memoir on Carl Wagner, in Ber. Bunsengesellschaft fiir Phys. Chem., vol. 95, p. 936 (In German). 

The transport of charged ions in alkali halides and, later on, in (insulating) ceramics is a distinct parepisteme, because electric fields play a key role. This large field is discussed in Schmalzried s 1995 book, already mentioned, and also in a review by one of the pioneers (Nowick 1984). This kind of study in turn led on to the developments of superionic conductors, in which ions and not electrons carry substantial currents (touched on again in Chapter 11, Section 11.3.1.1). 

H. Schmalzried, Solid State Reactions, (Verlag Chemie, Basel 1981). 

H. Schmalzried, Festkorperreaktionen Chemie des festen Zustandes, Verlag Chemie, Weinheim, 1971 Solid State reactions, Academic Press, New York, 1974. 

H. Schmalzried, in P. Barret (Ed.), Reaction Kinetics in Heterogeneous Chemical Systems, Elsevier, Amsterdam, 1975, p. 558. 

H. Schmalzried, in N.B. Hannay (Ed.), Treatise on Solid State Chemistry, Vol. 4, Plenum Press, New York, 1976, Chap. 5. 

Schmalzried, H. On the equilibration of solid phases. Some thoughts on Ostwalds contributions. Z. Physik. Chem. 2003, 217, 1281-1302. 

H. Schmalzried, in Chemical Kinetics of Solids. Weinheim VCH, 1995, Chapter 8. 

H. Schmalzried, in Metallurgical Chemstry, Proc. Symp. NPL, Teddington, England (O. Kubaschewski ed.). London HMSO, 1972, p. 39. 

Partial pressure as a variable. As mentioned in 2.1, many types of thermodynamic variables may be used in the construction of phase diagrams. The various rules of construction, based on the laws of chemical thermodynamics, which apply to the different types of phase diagrams have been discussed in several books and papers (for instance, Pelton and Schmalzried 1973, Okamoto 1991, Pelton 1991). Following a classification proposed by Pelton, the various, bidimensional, phase diagrams may be subdivided into three types as follows ... 

We have already noted that the concept of stoichiometric crystal is an extreme idealization of an effectively more complex reality. In the presence of extrinsic disorder, stoichiometry varies as a function of the chemistry of the coexisting phases and of T and P. To clarify this concept better, the procedure developed by Nakamura and Schmalzried (1983) to describe fayalite may be briefly recalled. 

Based on thermogravimetric experiments on the compound Fe2Si04 at various T and conditions, Nakamura and Schmalzried (1983) established that the extrinsic disorder of fayalite is conveniently represented by the equihbrium... 

Nakamura A. and Schmalzried H. (1983). On the nonstoichiometry and point defects in olivine. Phys. Chem. Minerals, 10 27-37. 

Schmalzried H. (1978). Reactivity and point defects of donble oxides with emphasis on simple silicates. Phy.. Chem. Minerals, 2 279-294. 

A number of important workers who, up to that time, had been working in relative isolation, now became more involved in CALPHAD conferences and publications. The Canadian group, led by Pelton, had evolved is own representation of thermodynamic quantities in a specific set of non-metallic systems (Pelton and Flengas 1969, Pelton and Schmalzried 1973, Bale and Pelton 1974) but found that many of the concepts being outlined for alloys could also be applied in their area. This was to eventually lead to a Facility for Analysis of Chemical Thermodynamics (F A C T) (Bale and Pelton 1979) and the foundation of the Centre of Research for Thermodynamic Calculations at Montreal. In due course there would be further collaboration (Thompson et al. 1983) between F A C T and the SOLGASMIX programme of Eriksson (1975). 

Mole fractions may not always be the most suitable composition variables for SE s. This is due to crystal structure conditions and the fact that a crystal is built from sublattices, x, on which SE s are distributed in the sense of thermodynamic (sub) systems [H. Schmalzried, A. Navrotsky (1975)]. This point, however, concerns the subject matter of the next section. 

In the case of nonideal solid solutions, the vacancies (or other point defects) by necessity interact differently with components A and B in their immediate surroundings. Therefore, the alloy composition near a vacancy differs from the bulk composition Nb. This is analogous to the problem of energies and concentrations of gas atoms dissolved in alloys under a given gas vapor pressure [H. Schmalzried, A. Navrotsky (1975)]. Let us briefly indicate the approach to its solution and transfer it to the formulations in defect thermodynamics. 

C contains the formation entropy and r is the coordination number of the vacancy. Thus, AJf j/r is the enthalpy per V-A bond in the sense of the thermodynamics of regular solutions [H. Schmalzried, A. Navrotsky (1975)]. For random A-B distributions, the probability of the configuration (/ a b) in the nearest neighbor shell of the vacancy V is... 

Martin, M, Pfeiffer, T Schmalzried, H. (1988) Kristallthermodynamik, Report, LJnivei.sitat Hannover... 

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