Congruently melting phases

The phase diagram for the Sr-Au system shows three congruently melting phases, /3-SrAu (970°C), SrAu2 (1085°C) and SrAu, (1040°C) four phases formed in peritectic reactions are also observed, Sr Au (640°C), SrjAu (590°C), y-Srj Au (750°C) and 5-Sr,Au2, which has a limited stability range from the eutectoid (725°C) to the peritectic reaction (770°C). Independent structural investigations confirm the forma-... 

Figure 3.3. Schematic representation of the diagrams for the alkali metals with a selected number of elements of the p-block. In each box the solid intermediate phases are represented in the positions approximately corresponding to their compositions (long bars congruent melting phases short bars non-congruent phases). In the top part of each box every mark corresponds to a characteristic composition of the liquid phase for which the formation of an associate ( liquid compound ) may be suggested, for instance by the presence of an extremum in the trend of some property of the liquid phase. The symbol 2 L shown for certain ranges of compositions in a few diagrams indicates the presence of a miscibility gap in the liquid state, that is two liquid phases.

When it melts, however, the melt then decomposes into two separate phases. On either side of the congruently- melting composition is a phase... 

Figure 2.18. Examples of binary phase diagrams in each of which one stoichiometric phase is formed. In the Mg-Ge system we have the congruently melting Mg2Ge (33.3 at.% Ge) in Au-Sb, AuSb2 is formed through a peritectic reaction. In the Pt-Ag system one compound at 47 at.%...

Figure 2.19. Examples of systems in which intermediate phases corresponding to small composition ranges are formed. These are SnTe (congruent melting), HfRu (congruent melting), ZrV2 (peritectic formation) and TaV2 (formed through a solid-state reaction).

Figure 3.50. The Yb-Cd binary phase diagram. The congruently melting compound YbCd57 is the first stable binary quasicrystal identified.

In the In-As phase diagram (see Fig. 6.18), the formation of only one compound, the congruently melting InAs, is observed. The assessed version of the diagram was reported by Okamoto (1992), whereas Chatillon et al. (1990) revised all the thermodynamic data and calculated an optimized version of the diagram. 

Figure 6.18. In-As phase diagram (at constrained pressure). Notice, (similarly to other III/V phase diagrams) the formation of the congruently melting 1 1 compound which gives two eutectics. The eutectic with In is practically coincident with In. As a consequence, for all the compositions from 0 up to 50 at.% As the primary crystallization of InAs may he obtained.

Lachwa, J. et al.. Condensed phase behaviour of ionic liquid-benzene mixtures congruent melting of a [emim][NTf2] C H inclusion crystal, Chem. Commun., 2445,2006. 

Fig. 3.33 Schematic drawing of phase diagram around GaAs composition. TJ denotes the incongruent melting temperature for stoichiometric GaAs and denotes the congruent melting temperature. The congruent melting composition is assumed to be in the As excess region.

The following two points are to be noted. The first is that, as shown in Fig. 3.45, the F p equals the congruent melting temperature F, F p being the temperature where the melt is coexistent with the solid phase. The composition of the melt, C e,(, which decides the composition of grown crystals, changes continuously with changing s- Only at C eit = composition... 

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