The B-C-N System

Suenaga et al. (1999) [16] produced nanoparticles and nanotubes by arc discharging and found by means of electron energy loss spectroscopy (EELS) that such materials consist of immiscible BN and C-layers. The growth mechanism was explained by using the calculated phase diagram sections in the B-C-N system according to [33, 244]. 

A remarkable variety of compounds in the Ca-(B,C,N) system has opened a window for research in related fields. With the elements boron, carbon and nitrogen, substance classes such as borocarbides, boronitrides, and carbonitrides can be considered to contain anionic derivatives of binary compounds B4C, BN, and C3N4. Until now, most compounds in these substance classes have been considered to contain alkali, alkaline-earth, or lanthanide elements. Lanthanide borocarbides are known from the work of Bauer [1]. Lanthanide boronitrides represent a younger family of compounds, also assigned as nitridoborates [2] following the nomenclature of oxoborates. 

Fig. 8.15 Concentration simplex of the La-B-C-N system. Combinations include one quaternary system, four ternary systems, and six binary systems.

In contrast, less is known about La-(CNx) compounds. The composition La2(CN2)3 was reported many years ago [43], without any structural information. Solid-state metathesis reactions of lanthanum chloride with Li2(CN2) or Zn(CN2) have recently brought up three series of the lanthanide compounds Ln2(CN2)3 [44], LnCl(CN2) [45], and Ln2Cl(CN2)N [46], Syntheses routes for Ln-(CNx) compounds containing new anions such as [C2N4] are to be developed, as well as for compounds in the La-B-C-N system (Fig. 8.15). 

Schulz S (2002) Synthesis, Structure and Reactivity of Group 13/15 Compounds Containing the Heavier Elements of Group 15, Sb and Bi 103 117-166 Seifert HJ, Aldinger F (2002) Phase Equilibria in the Si-B-C-N System. 101 1-58 Stahlke D, see Mahalakshmi L (2002) 103 85-116... 

B-C-O ring systems have been examined less often than B-C-N systems, presumably owing to the lack of... 

This paper gives an overview of experimental results and thermodynamic calculations in the Si-B-C-N system and its binary and ternary subsystems. 

The compositions of solid phases appearing in the Si-B-C-N system are indicated in the concentration tetrahedron as shown in Fig. 1. Some of them appear in different modifications. The basic crystallographic data of stable phases are given in Table 1. 

The CALPHAD method of computer coupling of phase diagrams and thermodynamics [24] was used to explore the phase equilibria in the Si-B-C-N system. Analytical descriptions of the Gibbs free energies for all stable phases and gaseous species of the system were established in the literature and by the... 

The ternary system Si-B-C was optimized in the scope of our work on the Si-B-C-N system [33, 34]. The other three ternary systems (Si-B-N, Si-C-N, B-C-N) could be calculated comprehensively by thermodynamic extrapolations since all solid phases have negligible ranges of solubility. Thermodynamic data of the ternary phases pSiCJti4 and Si2CN4, are not known yet, however they are reported not to be stable at the conditions treated here (P = 1 bar, T > 1300 K) [21]. 

Table 2. Gas species in the Si-B-C-N system. Thermodynamic data were used from [32]...

The descriptions of all ternary systems were combined in one dataset to simulate the phase equilibria in the quaternary Si-B-C-N system. The results of the thermodynamic calculations of individual systems are shown in the corresponding sections. Thermodynamic models used are the Redlich-Kister polynomial [39], extrapolations according to Muggianu et al. [40] and the compound energy formalism [41] to describe the solid solution phases )S-boron, SiBn, SiBg, SiBs and B4+ C. 

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