Differential thermal analysis of Ag–Ge–Se, Ge–Se charge materials in the process of their heating and Ag8GeSe6, GeSe2 compound synthesis

Enhancement of Power Factor for Inherently Poor Thermal Conductor Ag8GeSe6 by Replacing Ge with Sn

“…Figure b depicts the exothermic peaks across the phase transition from orthorhombic (space group Pmn2 1 ) to cubic (space group F 4̅ 3m ) structural units for Ag 8 SnSe 6 and Ag 8 GeSe 6 . The minor peak at 353 K in Ag 8 GeSe 6 is associated with ε to γ phase transition while peak around 415 K for both the samples is related to crystallization of Se into γ phase …”

“…The minor peak at 353 K in Ag 8 GeSe 6 is associated with ε to γ phase transition while peak around 415 K for both the samples is related to crystallization of Se into γ phase. 38 To understand further, we have performed Raman spectroscopy across the structural phase transition in the temperature range of 300−453 K (Figure 4). At room temperatures, we have observed three peaks at ∼193, 219 and 250 cm −1 for Ag 8 GeSe 6 , while two peaks at ∼205 and 213 cm −1 for Ag 8 SnSe 6 .…”

Comments on “Kinetics of non-isothermal crystallization and glass transition phenomena in Ga10Se87Pb3 and Ga10Se84Pb6 chalcogenide glasses by DSC” by Al-Agel et al.

“…These spectra do not show sharp diffraction peaks presenting crystalline phases. Neither they show any broad peak (halo) which should characterize the amorphous structure and which is typical also for chalcogenide glasses [2,3]. Moreover, these two curves are entirely identical; thus they cannot represent even noise.…”

Conceptual approach to thermal analysis and its main applications/Aproximación conceptual al análisis térmico y sus principales aplicaciones

“…In particular, the area under the curve (of an endothermic peak or exothermic), which produces a phase transition of first order, is directly proportional to the mass of substance involved and depends on the enthalpy of the process (eg latent heat, reaction enthalpy), the heat capacity of the substance and certain geometric factors (shape, particle size and degree of compaction of substances); in general, a peak area (A C ) is given by the equality [25]: (2) Where k is an associated thermal conductivity and constant c is a parameter related to the sample geometry and m is the mass. For a given mass k` it remains constant if the heating rate, particle size and location of the thermocouples in the dishes, which support the samples, are carefully controlled.…”