Vertical unseeded vapor growth of large α-GeTe crystals

Thermochemistry of (germanium + tellurium)

“…However, evidence in the literature that we have already discussed suggests that GeTe may not result necessarily from this procedure, but, rather, a mixture of the Te-rich phase Ge x Te and uncombined germanium. Several authors, notably Yellin and Gafni, (16) Abrikosov et al, (11) Korzhuyev et al, (17) and, most recently, Koren' et al (18) addressed the question of the composition of GeTe near exact stoichiometry. Whether our sample consisted of single-phase, exactly stoichiometric GeTe, as intended, or a mixture of Ge x Te and Ge is crucial for the interpretation of the calorimetric results and calculation of D f H°m.…”

“…Accordingly, we ask: how should the calorimetric results be interpreted if the measurements had actually been made on a mixture of Ge x Te and a small, but X-ray insensitive, quantity of Ge, rather than the assumed GeTe? Let us suppose that the rather extreme (in light of the literature on the nonstoichiometry of GeTe cited earlier) (11,(16)(17)(18) composition GeTe 1.1 had resulted from the synthesis. On the basis of that assumption, the initial composition of the (germanium + tellurium) mixture placed in the quartz tube would require a mass 0.33 g of Ge to have remained as a separate phase.…”