Phase Stability of 10mol%Sc2O3-1mol%CeO2-ZrO2 Ceramics

2008 ◽  
Vol 1074 ◽  
Author(s):  
Sergey Yarmolenko ◽  
Svitlana Fialkova ◽  
Devdas M. Pai ◽  
Jag Sankar
Keyword(s):  
Phase Transition ◽  
Sintering Temperature ◽  
Beta Phase ◽  
Slow Phase ◽  
Cubic Phase ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Oxygen Conductivity ◽  
Temperature Range ◽  
Β Phase

ABSTRACTScandia-doped zirconia is a very promising material for solid oxide fuel cells due to its high oxygen conductivity in the 700-850°C temperature range. 10 mol% Sc2O3 - 1 mol% CeO2 - ZrO2 ceramics were sintered at temperatures 1100-1600°C using different heating rates and dwell times. Ceramics sintered at temperatures higher 1300°C were found to exist in cubic phase at room temperature and exhibit slow phase transformation from cubic (c) to rhombohedral (beta) phase between 330 and 400°C. Analysis of c-β phase transition efficiency in the ceramics shows a strong correlation between the transition rate and sintering temperature. Kinetics of phase transitions were studied by high temperature X-ray diffractometry (HTXRD) and differential scanning calorimetry methods. The reversible c-β phase transition was found to have very wide hysteresis (45-70°C), which depends on sintering temperature and density. Coefficients of thermal expansion of c- and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25-800°C. Microstructural changes on the surface of the cubic phase due to c-β phase transition studied by SEM and AFM.

Phase Transitions and Thermal Expansion of 10mol%Sc2O3-1mol% CeO2-ZrO2 Ceramics

2007 ◽  
Author(s):  
Sergey Yarmolenko ◽  
Devendra Ray ◽  
Devdas Pai ◽  
Jag Sankar
Keyword(s):  
Thermal Expansion ◽  
Phase Transitions ◽  
Grain Structure ◽  
Slow Phase ◽  
Cubic Phase ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Operational Conditions ◽  
Β Phase

Phase transitions and CTE of 10mol%Sc2O3-1mol%CeO2-ZrO2 ceramics sintered from two commercial powders produced by Praxair Surface Technologies, USA and DKKK, Japan are studied. Morphology of powders and grain structure of ceramics were studied by SEM and AFM. Ceramics produced from Praxair powder exist in cubic phase while DKKK-based ceramics exhibit slow phase transformation from cubic to rhombohedral (β) phase at temperatures 350–400°C. c-β Phase transition temperature is 440°C obtained by high temperature x-ray diffractometry (HTXRD) and differential scanning calorimetry. Coefficients of thermal expansion of cubic and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25–800°C. These results can be further used for the optimal design of SOFC layered structures as well as for determination of their reliability and durability under operational conditions.

scholarly journals Phase transformations during continuous heating: effect of Sn addition on the microstructure of Ti-13Mo alloy

2020 ◽  
Vol 321 ◽  
pp. 05017
Author(s):  
M.G. de Mello ◽  
F.H. da Costa ◽  
R. Caram
Keyword(s):  
Lattice Parameter ◽  
Continuous Heating ◽  
Phase Precipitation ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Heat Treated ◽  
Kinetics Of

The addition of Sn to the Ti-Mo system can diminish the formation of ω phase and slow down the precipitation kinetics of α phase due to the low atomic diffusivity of Sn atoms in Ti. To explore α phase precipitation in Ti-13Mo and Ti-13Mo-6Sn (wt.%) alloys, differential scanning calorimetry (DSC) was applied using different heating rates to determine ω phase dissolution, α phase precipitation and β transus temperatures. The DSC results were then used to determine the aging heat treatment temperatures. Samples were heat-treated at 600 °C for 1 h and 24 h to examine microstructure features. The addition of Sn to Ti-13Mo alloy was found to increase the β phase lattice parameter, increasing β transus temperatures and resulting in microstructures with heterogeneous and coarser α phase precipitation.

scholarly journals Phase Transition and Melt-Recrystallization Behavior of Poly(Butylene Adipate) Investigated by Simultaneous Measurements of Wide-Angle X-Ray Diffraction (WAXD) and Differential Scanning Calorimetry (DSC)

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 75
Author(s):  
Mengfan Wang ◽  
Weiyu Cao
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Heating Process ◽  
Wide Angle ◽  
Melt Crystallization ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Simultaneous Measurements

Simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were carried out to investigate the phase transition and melting behaviors of poly(butylene adipate) (PBA). Thermal expansion changes along the a and b axes of the β form unit cell are different from each other during the heating process. At the beginning of the β to αH (high-temperature α phase) phase transition, the β phase melts very fast, while the recrystallization of the αH phase is delayed and slowed. With the further increment of the temperature, the melting rate of the β phase slows down, while the recrystallization of the αH phase accelerates. The diffraction peak intensity ratios of the β(020):β(110) and αH(020):αH(110) diffraction peaks during the first heating process have similar value. However, the above value is different from the value of α(020):α(110) during the following melt-crystallization process. This difference comes from the different orientations of the crystal lattices of the α and αH(β) crystals to the substrate plane, which indicates that the αH phase inherits the orientation of the β phase during phase transition and the orientation of αH form crystals is different from the α form crystals that crystallized from the melt.

TEM characterization of the α' and β phases in polycrystalline distrontium silicate (Sr2SiO4)

1992 ◽  
Vol 50 (1) ◽  
pp. 354-355
Author(s):  
Y. J. Kim ◽  
J. L. Shull ◽  
W. M. Kriven
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Atmospheric Pressure ◽  
Sintering Temperature ◽  
Major Phase ◽  
Space Group ◽  
Temperature Range ◽  
Β Phase ◽  
Tem Characterization

Two polymorphs, α' and β, are known to be major phases in pure distrontium silicate (Sr2SiO4) at atmospheric pressure. Fully dense pellets were fabricated by sintering chemically prepared powders in the temperature range of 900° to 1400°C for 1 to 5 hours. Their phases and microstructures were studied by TEM. At lower sintering temperatures such as 900°C, the major phase was orthorhombic α' (space group, Pmnb). The euhedral α' grains had a size of about 1 μm diameter (Fig. la). As the sintering temperature increased, the amount of monoclinic β phase (space group, P21/n) tended to increase. These β grains were usually irregular and twinned on {100}β or {001}β planes. Concentration of the electron beam on the grains gave rise to a disappearance of twins (Fig. lb).

X-ray diffraction study revealing phase coexistence in barium titanate stannate

2004 ◽  
Vol 19 (10) ◽  
pp. 2834-2840 ◽  
Author(s):  
Volkmar Mueller ◽  
Horst Beige ◽  
Hans-Peter Abicht ◽  
Christian Eisenschmidt
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Temperature Range ◽  
Xrd Study ◽  
Xrd Patterns ◽  
Tetragonal Phase Transition

In this paper, the results of a temperature dependent x-ray diffraction (XRD) study on BaTi0.95Sn0.05O3 (BTS-5) ceramics are compared with dielectric measurements. The orthorhombic-tetragonal phase transition at T2 = 306 K is found to proceed in a considerably wider temperature range than expected from the dielectric anomaly. Although the macroscopic properties of BTS-5 indicate a rather sharp ferroelectric phase transition at Tc = 358K, we observe anomalous XRD-patterns in a 25 K wide temperature range. This is interpreted in terms of mechanically clamped tetragonal and cubic phase, coexisting in the vicinity of Tc in grains with inhomogeneous Sn-distribution.

Structural phase transition in polycrystalline SnSe: a neutron diffraction study in correlation with thermoelectric properties

2016 ◽  
Vol 49 (6) ◽  
pp. 2138-2144 ◽  
Author(s):  
F. Serrano-Sánchez ◽  
N. M. Nemes ◽  
O. J. Dura ◽  
M. T. Fernandez-Diaz ◽  
J. L. Martínez ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase ◽  
Neutron Diffraction Study ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Temperature Range ◽  
Seebeck Coefficients ◽  
Structure Space ◽  
Arc Melting

SnSe has been recently reported as a promising and highly efficient thermoelectric intermetallic alloy. The present material has been prepared by arc melting, as mechanically robust pellets, consisting of highly oriented polycrystals. The evolution of its orthorhombic GeS-type structure (space groupPnma) and phase transition to TlI-type structure (space groupCmcm) at high temperature has been studiedin situby neutron powder diffraction (NPD) in the temperature range 295–873 K. This transition has been identified by differential scanning calorimetry measurements, yielding sharp peaks at 795 K. In addition, thermal transport properties were measured in a similar temperature range, and large Seebeck coefficients, as high as 1050 µV K−1at 625 K, were found. The analysis from NPD data demonstrates an almost perfect stoichiometry, Sn0.998(8)Se, that does not evolve with temperature, and a progressive decrease of the anharmonicity of the chemical bonds upon entering the domain of theCmcmstructure.

Determination of the melting enthalpy of β phase of poly(vinylidene fluoride)

e-Polymers ◽  
2013 ◽  
Vol 13 (1) ◽  
Author(s):  
Arkadiusz Gradys ◽  
Pawel Sajkiewicz
Keyword(s):  
Thermodynamic Stability ◽  
Vinylidene Fluoride ◽  
Melting Enthalpy ◽  
Dimethyl Formamide ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Β Phase ◽  
Α Phase ◽  
Poly Vinylidene Fluoride ◽  
Limited Temperature Range

Abstract Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared spectroscopy (FTIR) analyses of phase composition and of thermal properties of PVDF samples, crystallized at temperatures 27 - 155 °C by casting from N,N-dimethyl formamide (DMF) solution, are reported. Samples obtained at 27 °C contain only β crystal phase and with increase of casting temperature content of β phase decreases in favor of α phase. Evaluation of combined: phase content (WAXS) and melting heat (DSC), leads to two fold higher than for 100 % α phase value of 100% β melting enthalpy, ΔHβ0= 219.7 J.g-1, which may be justified by strong polar interactions in β phase TTT conformation. The relation ΔHβ0 > ΔHα0 leads either to the thermodynamic stability of β phase in whole temperature range (if Tmβ0 ≥ Tmα0) or to the limited temperature range of thermodynamic stability of α phase (if Tmβ0 < Tmα0).

Thermodynamic Properties of EuCl2 and the NaCl-EuCl2 System

2001 ◽  
Vol 56 (9-10) ◽  
pp. 647-652 ◽  
Author(s):  
F. Da Silva ◽  
L. Rycerz ◽  
M. Gaune-Escard
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Linear Equation ◽  
Scanning Calorimetry ◽  
Temperature Range

Abstract The temperature and enthalpy of the phase transition and fusion of EuCl2 were determined and found to be 1014 K, 11.5 kJ mol-1and 1125 K, 18.7 kJ mol-1 , respectively. Addition­ ally, the heat capacity of solid EuCl2 was measured by Differential Scanning Calorimetry in the temperature range 306 -1085 K. The results were fitted to the linear equation C0p,m = (68.27 + 0.0255 T/K) J mol -1 K-1 in the temperature range 306 -900 K. Due to discrepancies in the liter­ ature on the temperature of fusion of EuCl2, the determination of the NaCl-EuCl2 phase diagram was repeated. It consists of a simple eutectic equilibrium at Teut = 847 K with x(EuCl2) = 0.49.

Hydrogen permeability study of the thin Pd–Ag alloy membranes in the temperature range across the α–β phase transition

2006 ◽  
Vol 282 (1-2) ◽  
pp. 370-374 ◽  
Author(s):  
J OKAZAKI ◽  
D TANAKA ◽  
M TANCO ◽  
Y WAKUI ◽  
F MIZUKAMI ◽  
...  
Keyword(s):  
Phase Transition ◽  
Hydrogen Permeability ◽  
Temperature Range ◽  
Β Phase ◽  
Permeability Study

scholarly journals The α–β phase transition in volcanic cristobalite

2014 ◽  
Vol 47 (4) ◽  
pp. 1205-1215 ◽  
Author(s):  
David E. Damby ◽  
Edward W. Llewellin ◽  
Claire J. Horwell ◽  
Ben J. Williamson ◽  
Jens Najorka ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ambient Temperature ◽  
Volcanic Ash ◽  
Phase Identification ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
The Stability ◽  
First Time

Cristobalite is a common mineral in volcanic ash produced from dome-forming eruptions. Assessment of the respiratory hazard posed by volcanic ash requires understanding the nature of the cristobalite it contains. Volcanic cristobalite contains coupled substitutions of Al3+ and Na+ for Si4+; similar co-substitutions in synthetic cristobalite are known to modify the crystal structure, affecting the stability of the α and β forms and the observed transition between them. Here, for the first time, the dynamics and energy changes associated with the α–β phase transition in volcanic cristobalite are investigated using X-ray powder diffraction with simultaneous in situ heating and differential scanning calorimetry. At ambient temperature, volcanic cristobalite exists in the α form and has a larger cell volume than synthetic α-cristobalite; as a result, its diffraction pattern sits between ICDD α- and β-cristobalite library patterns, which could cause ambiguity in phase identification. On heating from ambient temperature, volcanic cristobalite exhibits a lower degree of thermal expansion than synthetic cristobalite, and it also has a lower α–β transition temperature (∼473 K) compared with synthetic cristobalite (upwards of 543 K); these observations are discussed in relation to the presence of Al3+ and Na+ defects. The transition shows a stable and reproducible hysteresis loop with α and β phases coexisting through the transition, suggesting that discrete crystals in the sample have different transition temperatures.

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