Medina-Cruz, Olga L.

Profile Picture

Filters

20051
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    Estudio de las propiedades térmicas de algunos vidrios y policristales de la forma A2BX4
    (2005) Medina-Cruz, Olga L.; Castellano-Rodríguez, Dorial; College of Arts and Science - Science; Quiñones, Luis M.; Velázquez Esov; Department of Physics; Quiñones, Wilfredo
    The properties of specific heat, thermal conductivity, and heat flow were studied in polycrystalline materials of the form A2BX4, like: Cs2CoCl4, Cs2ZnI4, [N(CH3)4]2CoCl4 and (NH4)2CrO4 elaborated by the methods of quick and slow evaporation, as well as, in vitreous materials like: SiO2: Al2O3: Sb2O3: CaO: Na2O: Cr2O3 and [N(CH3)4]2CoCl4: P2O5: Al2PO4: CaCO3 and the ceramic SiO2: Cr2O3: B2O3, obtained by the fusion method. To analyze these variables, each of these compounds was submitted to temperature variations in the range of 260K to 370K at constant volume, which allowed to register the behavior of the samples under a change of temperature. With the help of graphic analysis of the specific heat, thermal conductivity and heat flow as functions of the temperature, it was possible to evidence the phase transitions and anomalous behavior experienced by each compound. The polycrystals presented a transition of incommensurable phase to normal phase at 273K for Cs2ZnI4 and [N(CH3)4]2CoCl4, 290K for the compound (NH4)2CrO4 and the transition from commensurate to incommensurate at 291K for Cs2CoCl4, a fact that allowed to differentiate these materials from the glasses. Also, the transition due to the Jahn-Teller effect was registered for all materials: at 304K for Cs2ZnI4 and [N(CH3)4]2CoCl4, at 310K for (NH4)2CrO4, at 286K for Cs2CoCl4, and for the glasses it was around 309.55K. When comparing the results obtained with those found in published studies, for the same compounds it is found that there is agreement among these; even when the technique used by them is different to the one that we use in this study. The dynamic form of the technique used (thermoelectric camera) to measure the studied variables was extraordinarily effective, since it allowed the samples to carry out the processes of energy absorption and emission. This fact contributed to differentiate the structures of the materials in question. This can be better seen when observing the behavior of the heat flow when increasing the temperature, because an almost linear flow is registered, with smaller slope for the glasses than for the polycrystals, as expected. These curves show clearly the phase transitions and the effects produced by the properties of the elements in each compound. When comparing the results obtained for specific heat and thermal conductivity with data already established, we were able to classify these compounds as semiconductor materials in the case of the polycrystals and as insulators for the glasses, in the normal phase.