Thermal Diffusivity and Phase Transition of Rare Earth Manganites

2006 ◽  
Vol 321-323 ◽  
pp. 1695-1698 ◽  
Author(s):  
Migaku Kobayashi ◽  
Hirohisa Sato ◽  
Yoshihiko Hiyoshi ◽  
Naoki Kamegashira ◽  
Doh Jae Lee ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Oxygen Nonstoichiometry ◽  
Flash Method ◽  
X Ray ◽  
Increasing Temperature

Thermal diffusivity of nonstoichiometric PrMnO3 and NdMnO3 phases were measured by laser flash method from room temperature to 1100 K, in addition to the data of electrical conductivity, thermal analysis and high temperature X-ray diffractometry to detect the phase transition. The thermal diffusivity curve varied with increasing temperature and showed a clear anomaly with a sudden dip at the phase transition temperature. The transition temperature decreases with oxygen nonstoichiometry in each phase.

Phase Behavior of La1-xMnO3-1.5x with Trivalent Manganese Ion

2004 ◽  
Vol 449-452 ◽  
pp. 741-744 ◽  
Author(s):  
M. Kobayashi ◽  
Hirohisa Sato ◽  
Naoki Kamegashira
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Orthorhombic Phase ◽  
Ceramic Method ◽  
X Ray ◽  
Manganese Ion

Defect perovskite, La1-xMnO3-1.5x (x=0.00-0.10), was synthesized by conventional ceramic method and phase transition was measured by X-ray diffractometry, electrical conductivity, thermal diffusivity and thermal analysis. La1-xMnO3-1.5x (x=0.00-0.09) have single orthorhombic phase corresponding to GdFeO3 type perovskite structure at room temperature, while have rhombohedral structural at high temperature. The transition temperatures observed from electric conductivity, DSC, thermal diffusivity were mostly in agreement and they slightly decrease with increasing x.

Thermal Conductivities of Cs-M-O (M= Mo or U) Ternary Compounds

2009 ◽  
Vol 1215 ◽  
Author(s):  
Kazuyuki Tokushima ◽  
Kosuke Tanaka ◽  
Ken Kurosaki ◽  
Hiromichi Gima ◽  
Hiroaki Muta ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Flash Method ◽  
Ternary Compounds ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Thermal Diffusivities ◽  
Thermal Conductivities

AbstractThermal conductivities of Cs-M-O (M= Mo or U) ternary compounds, observed in the pellet-cladding gap region and in the pellet periphery in irradiated oxide fuels with high oxygen potentials, were investigated. Bulk samples of Cs2MoO4and Cs2UO4were prepared by hot pressing or spark plasma sintering, and their thermal diffusivities were measured by the laser flash method from room temperature to 823 K for Cs2MoO4and to 900 K for Cs2UO4. The thermal conductivities were evaluated from the thermal diffusivity and bulk density, and the specific heat capacity values available in the literature. The thermal conductivities of Cs2MoO4and Cs2UO4were quite low compared with UO2(e.g. 0.5 Wm−1K−1at 800 K for Cs2MoO4).

X-Ray Diffraction Study of the Phase Transition of the ${\rm Si}(111)(\sqrt{3} \times \sqrt{3})\mbox{-Ag}$ Surface

2003 ◽  
Vol 10 (02n03) ◽  
pp. 519-524 ◽  
Author(s):  
Toshio Takahashi ◽  
Hiroo Tajiri ◽  
Kazushi Sumitani ◽  
Koichi Akimoto ◽  
Hiroshi Sugiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Low Temperatures ◽  
Diffuse Scattering ◽  
Room Temperature ◽  
Bragg Reflection ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Displacive Phase Transition

The structure of the [Formula: see text] surface was studied at both room temperature and a low temperature of 50 K using grazing incidence X-ray diffraction. At low temperatures diffuse scattering was observed in addition to Bragg reflection. Least squares analyses for Bragg reflections using anisotropic Debye–Waller factors show that the structure at 50 K is consistent with an inequivalent triangle (IET) model, while the structure at room temperature is explained by a honeycomb-chained triangle (HCT) model with strong anisotropic Debye–Waller factors. From the temperature dependence of diffuse scattering, the phase transition temperature Tc and critical exponent β were determined to be about 150 K and 0.27. Some Bragg intensities showed discontinuous changes in their first derivatives at Tc. The results favor a displacive phase transition rather than an order–disorder one.

Phase transitions in KTP isostructures: correlation between structure and T c in germanium-doped RbTiOPO4

2003 ◽  
Vol 59 (5) ◽  
pp. 588-595 ◽  
Author(s):  
Stefan T. Norberg ◽  
Joacim Gustafsson ◽  
Bengt-Erik Mellander
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Room Temperature ◽  
Dielectric Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Distorted Octahedral Coordination ◽  
Distorted Octahedral ◽  
The Relationship ◽  
Germanium Concentration

Crystals of germanium-doped rubidium titanyl phosphate, Rb2(Ti)(Ge0.121Ti0.879)O2(PO4)2 (GeRTP#1) and Rb2(Ge0.125Ti0.875)(Ge0.225Ti0.775)O2(PO4)2 (GeRTP#2), have been structurally characterized from X-ray diffraction data at room temperature. In addition, a third structure, Rb2(TiO)2(PO4)2 (RTP), has been reinvestigated. The exchange of titanium for germanium results in a less distorted octahedral coordination around the two crystallographically independent titanium sites. Additionally, rubidium split-cation positions have been found in these doped RTP crystals. Dielectric measurements show that the phase-transition temperature, T c , decreases with increasing germanium concentration, and a direct correlation between the room-temperature split of the rubidium cations and T c has been discovered. General trends regarding the relationship between the room-temperature structures of KTP-like compounds and their T c values are discussed.

Powder Diffraction Data of Polymorphic Phases of Dicesium Cadmium Tetraiodide Cs2CdI4

1986 ◽  
Vol 1 (2) ◽  
pp. 35-36 ◽  
Author(s):  
V. Touchard ◽  
M. Louër ◽  
D. Louër
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Indexing Methods ◽  
X Ray ◽  
Two Phases

Introduction: Phase transition has been recently observed in Cs2CdI4 (Touchard, Louër, Auffrédic & Louër, 1986). Thermal analysis has shown that the transformation occurs at 122°C. By quenching, the high temperature phase (β) can be stabilized at room temperature. In the present work we report the X-ray diffraction powder data, at room temperature, for the two phases α- and β-Cs2CdI4. Both phases have been indexed automatically by using powder indexing methods.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

scholarly journals X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)2I3

1986 ◽  
Vol 41 (11) ◽  
pp. 1319-1324 ◽  
Author(s):  
H. Endres ◽  
H. J. Keller ◽  
R. Swietlik ◽  
D. Schweitzer ◽  
K. Angermund ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
Slight Variation ◽  
X Ray ◽  
Organic Metals ◽  
Β Phase ◽  
Α Phase

The structure of single crystals of the organic metals α- and β-(BEDT-TTF)2I3* was determined at 100 K, well below the phase transitions indicated by resistivity and thermopower measurements as well as by differential thermal analysis. In the α-phase no unusual change of the room temperature unit cell but a slight variation in the triiodide network and especially a more pronounced dimerization in one of the two donor stacks have been found. The β-phase develops a superstructure with a unit cell volume three times as large as that at room temperature and with pronounced distortions of the I3--ions.

scholarly journals Influence of the Al content on the phase transformations in Cu-Al-Ag alloys

2003 ◽  
Vol 28 (1) ◽  
pp. 33-38 ◽  
Author(s):  
A. T. Adorno ◽  
A. V. Benedetti ◽  
R. A. G. da Silva ◽  
M. Blanco
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Transition Temperature ◽  
Phase Transformations ◽  
Decomposition Reaction ◽  
Phase Decomposition ◽  
Stability Range ◽  
X Ray ◽  
Al Content ◽  
The Stability

The influence of the Al content on the phase transformations in Cu-Al-Ag alloys was studied by classical differential thermal analysis (DTA), optical microscopy (OM) and X-ray diffractometry (XRD). The results indicated that the increase in the Al content and the presence of Ag decrease the rate of the <FONT FACE=Symbol>b</font>1 phase decomposition reaction and contribute for the raise of this transition temperature, thus decreasing the stability range of the perlitic phase resulted from the b1 decomposition reaction.

Study of the Thermal Diffusivity Variation in Thin Duplex Steel Plates Welded by GTAW Process

2018 ◽  
Vol 930 ◽  
pp. 460-465
Author(s):  
Evandro Giuseppe Betini ◽  
Maurilio Pereira Gomes ◽  
Cristiano Stefano Mucsi ◽  
Temístocles de Souza Luz ◽  
Marcos Tadeu D'azeredo Orlando ◽  
...  
Keyword(s):  
Thermal Diffusivity ◽  
Welding Process ◽  
Laser Flash ◽  
Nitrogen Atmosphere ◽  
Steel Plates ◽  
Digital Data ◽  
Flash Method ◽  
Temperature Profiles ◽  
Butt Weld ◽  
Duplex Steel

This study describes the thermal diffusivity of thin duplex steel plates in the thickness direction measured using the laser-flash method after welding. The work reports the experimental efforts in recording temperature profiles of the grade UNS S32304 duplex steel during autogenous welding. The butt weld autogenous joints were carried out by the GTAW (gas tungsten arc welding) process with either argon or argon - 2% nitrogen atmospheres. The amount of nitrogen in the heat affected regions, after welding, was measured and correlated with the variation of the thermal diffusivity of the studied material. The temperature profiles were obtained using k-type thermocouples connected to a digital data acquisition system. Different thermal cycles and thermal diffusivity values were observed in the heat-affected zone (HAZ) for both samples. In the solidified zone (SZ) was observed similar increase of the thermal diffusivity values for the plates welded with pure argon and argon plus nitrogen atmosphere.

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