Determination of the Kind for Actual Ferroelectrics, Together with Examination of the Characters of Their Paraelectric Phase Transformations

1964 ◽  
Vol 136 (3A) ◽  
pp. A753-A758 ◽  
Author(s):  
Kêitsiro Aizu
Keyword(s):  
Phase Transformations ◽  
Paraelectric Phase

Resistiometric determination of phase transformations in VHx and VDx

1980 ◽  
Vol 75 (2) ◽  
pp. 207-222 ◽  
Author(s):  
M.W Pershing ◽  
G Bambakidis ◽  
J.F Thomas ◽  
R.C Bowman
Keyword(s):  
Phase Transformations

scholarly journals Crystalline forms of silver iodide II: Determination of phase transformations

2007 ◽  
Vol 72 (8-9) ◽  
pp. 857-868 ◽  
Author(s):  
Marija Vukic ◽  
Dragan Veselinovic ◽  
Vesna Markovic
Keyword(s):  
Phase Transition ◽  
Phase Transformations ◽  
Heating Rate ◽  
Silver Iodide ◽  
Room Temperature ◽  
Sample Heating ◽  
Crystalline Forms

In order to obtain appropriate forms of AgI (?- and ?-), a procedure was developed to synthesize AgI at room temperature (23?C), whereby samples of varying crystallographic purity and of varying crystallographic contents of the different forms were obtained. This paper presents the results of investigations of the influence of the manner of preparation of ?-AgI and ?-AgI samples and the sample heating rate on the phase transformations and their temperatures. During the heating of non-ground, ground and pressed synthesized AgI samples, the phase transformations and the corresponding temperatures for one ?-AgI and four ?-AgI samples with different ?-AgI contents (representing a crystallographic impurity) were identified. The following phase transformations were observed for the non-ground AgI samples: ?-AgI ? ?-AgI at 149.6?C (for the ?-AgI sample) and ?-AgI ? ?-AgI at 148.7?C or 148.2?C for the ?-AgI samples with a minimum content of ?-AgI (less than 7 %), as a crystallographic impurity. The phase transition ?-AgI ? ?-AgI was irreversible because ?-AgI was obtained whenever the samples were heated up to 260?C. Manual sample grinding, as well as pressing at p1 = 650 MPa and p2 = 900 MPa resulted in the ?-AgI ? ?-AgI phase transition in all the investigated cases. .

scholarly journals Phase transformations and thermal conductivity of the In-Ag alloys

10.30544/488 ◽  
2020 ◽  
Vol 26 (3) ◽  
pp. 239-251
Author(s):  
Dragan Miroslav Manasijevic ◽  
Ljubiša Balanović ◽  
Ivana Markovic ◽  
Milan Gorgievski ◽  
Uros Stamenkovic ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transformations ◽  
Silver Content ◽  
Calphad Method ◽  
Flash Method ◽  
Scanning Calorimetry ◽  
Phase Transition Temperatures ◽  
Equilibrium Solidification

Phase transformations and thermal conductivity of three In-Ag alloys with 5, 15, and 45 wt.% of Ag were experimentally investigated in the present work. Phase transition temperatures were measured using differential scanning calorimetry (DSC). DSC heating scans were compared with the equilibrium and non-equilibrium solidification paths, calculated by using optimized thermodynamic parameters from literature and calculation of phase diagrams (CALPHAD) method.  The flash method was employed for the determination of thermal diffusivity and thermal conductivity of the investigated alloys in the temperature range from 25 to 100 °C. It has been found that an increase in silver content does not lead to an increase in the thermal conductivity of the investigated alloys. Thermal conductivities for all three investigated In-Ag alloys slightly decrease with temperature increasing.

scholarly journals EXPERIMENTAL AND THEORETICAL DETERMINATION OF SPECIFIC HEATS, PHASE TRANSFORMATIONS TEMPERATURES AND ENTHALPY OF Fe-C-Cr-Ni ALLOWS

2020 ◽  
Author(s):  
Svetlana SOROKINA ◽  
Bedřich SMETANA ◽  
Ľubomíra DROZDOVÁ ◽  
Monika KAWULOKOVÁ ◽  
Simona ZLÁ 
Keyword(s):  
Phase Transformations ◽  
Theoretical Determination ◽  
Specific Heats

scholarly journals New advances in the laboratory characterization of refractories: testing and modelling

2017 ◽  
Vol 114 (6) ◽  
pp. 610 ◽  
Author(s):  
Jacques Poirier ◽  
Eric Blond ◽  
Emmanuel de Bilbao ◽  
Rudy Michel ◽  
Antoine Coulon ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Numerical Analyses ◽  
Laboratory Methods ◽  
Corrosion Kinetics ◽  
Laboratory Characterization ◽  
Deformation Phase ◽  
Macroscopic Deformation

This publication presents new advances in the field of refractories characterization. These laboratory methods that combine experiments and numerical analyses and concern both the thermomechanical and thermochemical behaviour are illustrated through different examples: identification of asymmetrical creep, determination of elastic and inelastic properties, measurements of macroscopic deformation, phase transformations or corrosion kinetics. These advanced techniques offer the refractory community new opportunities to improve the knowledge and the prediction of the phenomena of degradation of the refractories.

Neutron structures of ammonium tetrafluoroberyllate

1999 ◽  
Vol 55 (1) ◽  
pp. 17-23 ◽  
Author(s):  
R. C. Srivastava ◽  
W. T. Klooster ◽  
T. F. Koetzle
Keyword(s):  
Hydrogen Bonding ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Accurate Determination ◽  
Mirror Plane ◽  
Accurate Information ◽  
X Ray ◽  
The Past ◽  
Hydrogen Bonding Interactions

It is thought that hydrogen bonding is responsible for the ferroelectricity in ammonium tetrafluoroberyllate, (NH_{4})_{2}BeF_{4}. In the past X-ray data have been collected, but these did not permit accurate determination of the H-atom positions. In order to obtain more accurate information the neutron structures have now been determined for the paraelectric and ferroelectric phases. Going from the paraelectric to the ferroelectric phase, both the BeF_4^{2-} and the NH_4^+ ions rotate and shift from the mirror planes of the paraelectric phase. This results in removal of the mirror-plane symmetry and formation of a superlattice with the a axis doubled. Along the polar c axis, the NH_4^+ ions move towards the BeF_4^{2-} ions within chains of molecules and the chains move slightly relative to one another. The rotations and translations give rise to stronger hydrogen-bonding interactions.

Etude quantitative de l'énergie libre de PbZrO3 pur et dopé avec Nb2O5

1969 ◽  
Vol 47 (22) ◽  
pp. 2439-2443 ◽  
Author(s):  
L. Benguigui ◽  
H. Hervet
Keyword(s):  
Free Energy ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Temperature Phase ◽  
Phase Determination ◽  
Electrical Field ◽  
Antiferroelectric Phase ◽  
Field Temperature ◽  
Heat Transition

Pure and Nb2O5 doped PbZrO3 exhibit the following phases: antiferroelectric, ferroelectric, and paraelectric. By means of measurements of heat transition, dielectric constant in paraelectric phase, determination of electrical field – temperature phase diagrams, we calculate the free energy of each phase. Given that the free energy can be developed in powers of the polarization, we show the coefficients of the ferroelectric phase are slightly modified by the addition of Nb2O5, while those of the antiferroelectric phase vary by a factor greater than two.

scholarly journals Investigations of Temperatures of Phase Transformations of Low-Alloyed Reinforcing Steel within the Heat Treatment Temperature Range

2017 ◽  
Vol 62 (2) ◽  
pp. 891-897 ◽  
Author(s):  
T. Kargul
Keyword(s):  
Phase Transformations ◽  
Treatment Temperature ◽  
Protective Atmosphere ◽  
Eutectoid Transformation ◽  
Dsc Analysis ◽  
Temperature Range ◽  
Proeutectoid Ferrite ◽  
Temperatures Of Phase Transformations ◽  
Tempcore Process

AbstractThe paper presents the results of DSC analysis of steel B500SP produced in the process of continuous casting, which is intended for the production reinforcement rods with high ductility. Studies were carried out in the temperature range below 1000°C in a protective atmosphere of helium during samples heating program. The main objective of the study was to determine the temperature range of austenite structure formation during heating. As a result of performed experiments:Ac1s,Ac1f– temperatures of the beginning and finish of the eutectoid transformation,Ac2– Curie temperature of the ferrite magnetic transformation and the temperature Ac3of transformation of proeutectoid ferrite into austenite were elaborated. Experimental determination of phase transformations temperatures of steel B500SP has great importance for production technology of reinforcement rods, because good mechanical properties of rods are formed by the special thermal treatment in Tempcore process.

scholarly journals Solid-Solid Phase Transformations and Their Kinetics in Ti-Al-Nb Alloys

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1991
Author(s):  
Benedikt Distl ◽  
Katja Hauschildt ◽  
Florian Pyczak ◽  
Frank Stein
Keyword(s):  
Phase Transformations ◽  
Heating Rate ◽  
Solid Phase ◽  
Thermal Analyses ◽  
Order Type ◽  
Heating Rates ◽  
Transformation Temperatures ◽  
Intermetallic Materials ◽  
Reduction Of Co2

The application of light-weight intermetallic materials to address the growing interest and necessity for reduction of CO2 emissions and environmental concerns has led to intensive research into TiAl-based alloy systems. However, the knowledge about phase relations and transformations is still very incomplete. Therefore, the results presented here from systematic thermal analyses of phase transformations in 12 ternary Ti-Al-Nb alloys and one binary Ti-Al measured with 4–5 different heating rates (0.8 to 10 °C/min) give insights in the kinetics of the second-order type reaction of ordered (βTi)o to disordered (βTi) as well as the three first-order type transformations from Ti3Al to (αTi), ωo (Ti4NbAl3) to (βTi)o, and O (Ti2NbAl) to (βTi)o. The sometimes-strong heating rate dependence of the transformation temperatures is found to vary systematically in dependence on the complexity of the transformations. The dependence on heating rate is nonlinear in all cases and can be well described by a model for solid-solid phase transformations reported in the literature, which allows the determination of the equilibrium transformation temperatures.

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