Borides homogeneity range

Little information is available on homogeneity ranges and defect structures in the dodecaborides. The only variation from stoichiometry in these borides is for YB,2i the limiting phase determined by density measurements is Yq92B,2. This result can be attributed to the size of Y which is the maximum for metals that form the dodecaborides. Attempts to prepare DyB,2 with a nonstoichiometric composition are conclusive. ... 

Besides the homogeneity ranges of the silicon borides mainly phase diagram data concerning the liquidus and the silicon solvus were published. The eutectic temperature between SiBg and silicon was calculated to 1658 K [36] (1657 K in the Scheil schemes) in good agreement with measurements with experimental data [52, 56, 61]. 

Bolmgren H (1994) On the crystal structure and homogeneity range of rhombohedral silicon boride. Report UUIC-B18-266. Institute of Chemistry, Uppsala University, Sweden... 

Figure 1. (a) Crystal structure (P6/mmm) of the refractory di-borides [Fahrenholtz, 2007, Li, 2010] and (b) Zr-B phase diagram showing very narrow homogeneity range for ZrB [McHale, 1994]... 

While most of the binary carbides and nitrides considered above form unlimited homogeneous solid solutions, some other 5 and p elements (B, Be, Al, Mg, etc.) have only a low solubility in these phases. As their content in carbides and nitrides increases, ternary compounds with very specific crystal structures are formed which were reviewed by Alyamovsky et al (1981) and Goldschmidt (1967). It is well known (see Samsonov, Serebryakov and Neronov (1975)) that B or transition metal borides do not form unlimited solid solutions, when interacting with MX phases (X = C, N) and single-phase TiNjBj, compounds exist over a narrow composition range for example, when z + y = 0.62-0.94, y < 0.03 (see Alyamovsky, Zainulin and Shveikin (1976)). As the B/N ratio increases. 

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