Authors:V. A. Drebushchak, S. N. Dementiev, and Yu. V. Seryotkin
stellerite, with two close peaks one by one. The first one (∼200 °C) is narrow and high and the second one (∼250 °C) is broader and smaller. The first peak was reported to be the first-order phasetransition with the step change of 3.24% in the UC volume and
Authors:Ke Liu, Xiao-Lin Zhou, Hai-Hua Chen, and Lai-Yu Lu
]. Although several research groups have experimental and theoretically investigated the pressure induced phasetransitions in TiN using different methods. For example, Zhao et al. [ 13 ] investigated the behavior of TiN using axial X-ray diffraction under
has been investigated for almost two decades and its ambient and sub-ambient phases have been well characterized: it has an orthorhombic structure with space group Fdd 2 below its ferro-paraelectric phasetransition at T c = −126 °C, and a
properties and phasetransition temperatures of (NH 4 ) 2 Co(SO 4 ) 2 ·6H 2 O crystals have not previously been reported. Further, some questions about Tutton salts are still open, especially those related to the nature of their structural changes and their
There are several approaches for the description of phase transitions (PT). leading to different classification schemes:ApproachClassification scheme bythermodynamicorder (after Ehrenfest)kineticreversibility, quenchability, hysteresisstructuralrelationship of crystallographic axes before and after PTmechanisticactual migration path of atoms during PT The most important techniques for investigating PT include DTA and DSC thermo-optical analysis, melastic neutron scattering, IR and Raman spectroscopy and elastic X-ray and neutron diffraction. The latter, as dependent on the temperature, can give indications on the mechanism of PT. The appropriate application of these techniques is demonstrated on the example of the polymorphism of KPO3.
Authors:M. de la Rubia, R. Alonso, J. de Frutos, and A. López-Garcia
The objective of this study is to determine the influence of partial substitutions of Ti4+ by isovalent Hf4+ in the perovskite-type crystalline structure of PbTiO3. Different samples over the whole composition range (0 ≤ x≤1) in the PbTi1-xHfxO3 family have been prepared. Phase transitions have been determined by thermal analysis (differential scanning calorimeter:
DSC) and complex impedance spectroscopy (IS) over a wide temperature range. As a consequence of the cation replacement the
changes that take place in the different phase transition temperature are reported. By both techniques, thermal analysis and
electrical characterization, it is shown that for all compositions prepared there is only one phase transition in a temperature
range between 230 and 460 °C. With these results and the previously known crystalline structure of pure PbTiO3 and PbHfO3 perovskites, the phase diagram of the PbTi1-xHfxO3 family is presented including a morphotropic phase transition at x ~ 0.5.
Authors:Alfredo Román-Tejeda and Heriberto Pfeiffer
phasetransition reversed when the process was performed at 500 °C or higher temperatures. Of course, a part of the ceramic reacted to produce lithium carbonate. These findings are all in good agreement with the literature, where it has been shown that α
Authors:M. Arai, T. Sakuma, T. Atake, and H. Kawaji
The phase transition and the crystal structures of CuITe were investigated by differential thermal analysis and X-ray powder
diffraction measurements in the temperature range between 300 and 683 K. The new phase transition in CuITe was observed at
592 K. The enthalpy of transition is ΔH=0.125 kJ mol-1. The new phase above 592 K belongs to tetragonal system with the space group I41/amd.
Authors:George G. G. de Oliveira, Humberto G. Ferraz, Patrícia Severino, and Eliana B. Souto
The aim of this article was to analyse the phasetransition and dehydration processes of nevirapine using DSC and thermogravimetry differential thermal analysis (TG-DTA).
Materials and methods
Nevirapine was provided by the