Multinary systems

One practical problem of the determinant method is the common unavailability of thermodynamic data and phase diagrams for multiphase compounds. For practical applications, an estimate obtained from data for binary compounds of the multinary system may be useful. 

The class of oxide materials has greatly benefited from the chemical exploration of multinary systems, virtually right from the beginning. Thus, besides a number of binary compounds, mainly in use as structural ceramics, there is an impressive pleAora of multinary oxide materials being applied as functional, as well as structural ceramics. In some instances these are even... 

Tan = 1550°C the binary eutectic temperatures 1362°C (quartz-diopside), 1270°C (diopside-anorthite), and 1368°C (quartz-anorthite) and the ternary eutectic temperature of 1200 °C. The composition of the ternary eutectic is 30 mass% quartz, 33 mass% diopside, and 37 mass% anorthite (Clark et al., 1962 Osborn and Tail, 1952). The ternary phase diagram discussed above refers to high-fired calcareous UMtic clays with the four components Si02, AI2O3, CaO, and MgO, but fails to incorporate an important fifth component such as Fe203. Hence, even more complex phase relations must be considered in appropriate multicomponent (quaternary, quinary, hexanary,... multinary) systems. 

The reason for uncommon phase diagram often lies in the polydispersity of the polymer sample, which means that we are strictly speaking no longer dealing with ternary but with multinary systems, for which the representation of phase diagrams requires a projection into a plane. In the present case, the polydispersity is due to the... 

Polymer-derived ceramics have been investigated in the last two decades concerning their high temperature oxidation behavior (i.e., usually temperatures exceeding 1000 °C and oxidizing environments such as air or combustion atmosphere). Mainly ternary and multinary systems based on the Si-M-O-C and Si-M-C-N-O systems (M = B, Al, Zr) were tested and showed passive oxidation behavior. (Chollon, 2010) Within this context, they can be considered as behaving to some extent like silica formers (e.g., silicon, metal silicides, SiC or SijN ). 

Jansen M, Jaschke B, Jaschke X (2002) Amorphous Multinary Ceramics in the Si-B-N-C System. 101 137-192... 

The same reasoning may hold for the virtual absence of transition metal dicarbides with (C2) anions. On the other hand, stable multinary compounds in A-M-(BNx), AE-M-(BNx), or Ln-M-(BNx) systems can exist with an electron-rich transition metal (M), similar to the known ternary dicarbides AM(C2) with A=alkali and M = Pd, Pt [25]. In these cases the valence electrons provided from A or AE metals fill the bonding (BNx)" or (C2) levels, and the transition metal retains an approximate d ° configuration. 

M. Jansen, T. Jaeschke, B. Jaeschke, Amorphous multinary ceramics in the Si-B-N-C system in Structure and Bonding, Vol. 101 (Ed. M. Jansen), Springer-Verlag, Berlin, Heidelberg, 2002, p. 137. 

This is in agreement with experiment, according to which no solid state syntheses of multinary compounds within the system Si/B/N/C from the binary border phases have been successful so far (for the corresponding thermodynamic considerations cf. [9]). In the course of the past decades, however, considerable progress has been achieved in the synthesis of multinary compounds by applying an alternative synthetic approach via molecular and polymeric intermediates (cf. Fig. 1). 

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