Te Phase Diagram Research Articles

Write-Erase Characteristics of Phase Change Optical Recording in Ga–Se–Te Systems

Reversible optical changes in a thin-film system of parylene/Tez(GaxSe1-x)1-z film (0.6≤z≤0.9, 0≤x≤0.3)/parylene structure has been studied by measuring the time required to crystalline from the amorphous state (the erasing time) and the number of reversible reflectance changes occurring between amorphous (written) and crystalline (erased) states. For a specimen with a Ga composition of x=0.15, the erasing time is about 1 µs. From a discussion of the Ga–Se–Te phase diagram, it becomes clear that the optimum composition showing write-erase characteristics is obtained at an eutectic point, in which the segregation is not caused and many cycle operations are possible. The SIC (Surface Induced Crystallization) model seems to be suitable for explaining the erasing process in the chalcogenide thin films.

Calculation of some thermodynamic properties and the phase diagram of the PbTe system

The strongly associated regular solution model has been used to calculate the phase diagram of the PbTe system, and most of the thermodynamic vuantities of the PbTe livuid alloys at 1200 K, for which evperimental values were available in the literature. These are the molar partial and miving enthalpies, entropies and Gibbs free energies. The dissociation evuilibrium constant and the pair interaction parameters used in the calculation were derived from evperimental values for both the molar partial enthalpies at infinite dilution and the enthalpy of miving at 50 at.% Te. The PbTe phase diagram has been calculated using the aforementioned parameters, and compared with the data reported in the literature. Agreement is generally vuite good between calculated and evperimental results, although we assume a negligible solubility range for PbTe in the solid state.

Phase diagram of the ternary system GeSbTe. I. The subternary GeTeSb 2Te 3Te

The GeTeSb 2Te 3Te phase diagram was investigated using differential thermal analysis, differential scanning calorimetry, thermogravimetry, powder X-ray diffraction and metallographic techniques. Isopleths of four composition sections were constructed. Five transitory reactions (U type) were characterized with compositions in the range 8.5–15 at.% Ge and about 84.5 at.% Te and temperatures very close one of the other. There are also indications of a eutectoid reaction at about 45 at.% Ge and 52 at.% Te. Seven isothermal sections are presented.

Transition metal-chalcogen systems viii: The CrTe phase diagram

The CrTe phase diagram was investigated in the composition range 30–100 at.% Te using differential thermal analysis and powder diffraction methods. Six NiAs-related phases were characterized between 52.4 and 62 at.% Te. Two of them, hexagonal Cr 1− x Te (52.4–53.5 at.% Te) and monoclinic Cr 3Te 4-h (53.5–59.3 at.% Te), are high temperature phases. At lower temperatures monoclinic Cr 3Te 4-l (56.4–59.2 at.% Te) and trigonal Cr 2Te 3 (59.5–60.0 at.% Te) are stable. Two phases, monoclinic Cr 5Te 8-m (59.6–61.5 at.% Te) and trigonal Cr 5Te 8-tr (61.5–62.0 at.% Te), were found on the tellurium-rich side of this phase system. At 75 at.% Te monoclinic CrTe 3, a novel polytelluride, is formed in a peritectic reaction at 753 K. There are also indications of the formation of another tellurium-rich phase at about 70 at.% Te and 734 K.