Phase Transition and Thermal Expansion of Ba3RB3O9 (R = Sm–Yb, and Y)

2017 ◽  
Vol 36 (8) ◽  
pp. 763-769 ◽  
Author(s):  
Rayko Simura ◽  
Shohei Kawai ◽  
Kazumasa Sugiyama
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Room Temperature ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Melting Temperatures ◽  
Type Phase

AbstractHigh temperature powder X-ray diffraction measurements of Ba3RB3O9 (R=Sm–Yb, and Y) were carried out at temperatures ranging from room temperature to just below the corresponding melting temperatures (1,200–1,300 °C). No phase transition was found for the H-type phase (R$\overline 3 $) with R=Sm–Tb and the L-type phase (P63 cm) with R=Tm–Yb. On the other hand, phase transition from the L phase to the H phase was observed for R=Dy–Er, and Y at around 1,100–1,200 °C. The obtained axial thermal expansion coefficient (ATEC) of the a-axis was larger than that of the c-axis for the H phase, and the ATEC of the c-axis was larger than that of the a-axis for the L phase. The observed anisotropic nature of ATEC is attributed to the distribution of the BO3 anionic group with rigid boron–oxygen bonding in the structures of the H and L phases.

Behaviors of the Zr–1.0Sn–0.39Nb–0.31Fe–0.05Cr Alloy at High Temperature

2011 ◽  
Vol 399-401 ◽  
pp. 80-84
Author(s):  
Yi Yuan Tang ◽  
Jie Li Meng ◽  
Kai Lian Huang ◽  
Jian Lie Liang
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
High Temperature ◽  
Oxide Film ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thin Oxide Film ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Phase transformation of the Zr-1.0Sn-0.39Nb-0.31Fe-0.05Cr alloy was investigated by high temperature X-ray diffraction (XRD). The XRD results revealed that the alloy contained two precipitates at room temperature, namely β-Nb and hexagonal Zr(Nb,Fe,Cr,)2. β-Nb was suggested to dissolve into the α-Zr matrix at the 580oC. Thin oxide film formed at the alloy’s surface was identified as mixture of the monoclinic Zr0.93O2and tetragonal ZrO2, when the temperature reached to 750oC and 850 oC. The thermal expansion coefficients of αZr in this alloy was of αa = 8.39×10-6/°C, αc = 2.48×10-6/°C.

Reinvestigation of the structure of BaCuSi2O6 – evidence for a phase transition at high temperature

2004 ◽  
Vol 60 (5) ◽  
pp. 491-495 ◽  
Author(s):  
Karine M. Sparta ◽  
Georg Roth
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Structural Phase ◽  
Original Structure ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Barium Copper

Superstructure reflections have been observed in the room-temperature X-ray diffraction pattern of BaCuSi2O6, barium copper disilicate. The tetragonal structure has a fourfold unit-cell volume compared with the original structure determined by Finger et al. [(1989), Am. Mineral. 74, 952–955]. At T s = 610 K BaCuSi2O6 undergoes a structural phase transition upon which the superstructure reflections disappear. The description of the structure in the larger cell removes the crystal-chemical inconsistencies observed for the original structure.

A high-temperature X-ray diffraction study of the NiO–Li2O system

1971 ◽  
Vol 4 (4) ◽  
pp. 293-297 ◽  
Author(s):  
C. J. Toussaint
Keyword(s):  
Crystal Structure ◽  
Phase Diagram ◽  
Thermal Expansion ◽  
High Temperature ◽  
Transition Temperature ◽  
Diffraction Study ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystallographic Study

A crystallographic study of the system Ni2+ 1−2x Ni3+ x Li+ x O has been carried out. The crystal structure of the material in the range 0≤x≤0.4 at room temperature and up to 1000°C has been studied. The principal coefficients of thermal expansion and the phase diagram are given. The structural rhombohedral → face-centred cubic transition temperature of NiO has been determined.

The thermal expansion and high temperature transformation of SnS and SnSe*

1979 ◽  
Vol 149 (1-2) ◽  
Author(s):  
Heribert Wiedemeier ◽  
Frank J. Csillag
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Melting Point ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
Orthorhombic Modification ◽  
Temperature Transformation ◽  
Increasing Temperature

AbstractThe thermal expansion of SnS and SnSe has been studied above room temperature up to the melting point of 1163 ± 5K and 1135 ± 5K, respectively, by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The changes of the lattice parameters indicate that the atomic positions in the (010) plane approach a square planar arrangement with increasing temperature. The transformation of SnS and SnSe from orthorhombic to a pseudotetragonal orthorhombic modification with

Phase transition and thermal expansion coefficient of leucite ceramics with addition of SiO2

2009 ◽  
Vol 24 (6) ◽  
pp. 1989-1993 ◽  
Author(s):  
Juan Paulo Wiff ◽  
Yoshiaki Kinemuchi ◽  
Shimako Naito ◽  
Ayako Uozumi ◽  
Koji Watari
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Intermediate Phase ◽  
Linear Thermal Expansion ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Before And After

In this work, the influence of SiO2 additions in leucite ceramics on the bulk linear thermal expansion coefficient (TEC) especially during the phase transition, has been studied. Thermal expansion and x-ray diffraction measurements at high temperatures were carried out to characterize the tetragonal-cubic phase transition. TEC for reference and SiO2-added leucite samples exhibited similar behavior as a function of temperature. Before and after the phase transition, the TEC values were similar to those observed in non-SiO2-added samples, whereas during the phase transition, a maximum TEC value was observed and it tends to decrease as the SiO2 addition increases. This behavior could be caused by the formation of an intermediate phase with an extremely high TEC (70 × 10–6 °C−1) during the phase transformation. Furthermore, the results suggest that as the intermediate phase is partially suppressed via SiO2 addition, the cubic phase can be partially stabilized at temperatures as low as 200 °C.

Investigation of tetragonal distortion in the PbTiO3–BiFeO3 system by high-temperature x-ray diffraction

1995 ◽  
Vol 10 (5) ◽  
pp. 1301-1306 ◽  
Author(s):  
V.V.S.S. Sai Sunder ◽  
A. Halliyal ◽  
A.M. Umarji
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Tetragonal Distortion ◽  
X Ray Diffraction ◽  
Solution System ◽  
X Ray ◽  
Lattice Constants ◽  
Solid Solution System ◽  
Different Temperatures

Compositions in the (Pb1−xBix (Ti1−xFex)O3 solid solution system for x ⋚ 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25–700 °C) for compositions (x = 0–0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature (TC) for compositions near the morphotropic phase boundary (MPB) (x ≃ 0.7). Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction.

Nonlinear thermal expansion in Li2NiMn3O8

2008 ◽  
Vol 23 (3) ◽  
pp. 224-227
Author(s):  
Lingmin Zeng ◽  
Yeqing Chen ◽  
Wei He ◽  
Liangqin Nong
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Linear Thermal Expansion ◽  
Lithium Ion ◽  
Entire Temperature Range ◽  
X Ray Diffraction ◽  
Spinel Type ◽  
X Ray ◽  
Temperature Range

A lattice thermal expansion study on Li2NiMn3O8, a high-voltage cathode material for lithium-ion batteries, was carried out by high-temperature X-ray diffraction from room temperature to 973 K. Rietveld refinement of a high-quality room-temperature diffraction pattern confirmed that Li2NiMn3O8 has the cubic Al2MgO4 spinel type of crystal structure. The analysis of the high-temperature X-ray diffraction patterns showed that the Li2NiMn3O8 structure remained stable and no phase transition was detected over the temperature range from 298 to 973 K. As expected, the value of lattice parameter a or unit cell volume V increases with increasing temperature. The increase in a or V is linear only in the low-temperature region and nonlinear over the entire temperature range from 298 to 973 K. Least-squares analysis of the data for a or V showed the thermal expansion of a or V for Li2NiMn3O8 can best be fitted by a 3-degree polynomial function of temperature. The linear thermal expansion coefficients for a and V averaged over the entire temperature range from 298 to 973 K were also calculated, and αTa=1.10×10−5 K−1; αTV=3.29×10−5 K−1.

Anisotropic Thermal Expansion of Barium Hexaferrite Using Dynamic High-temperature X-ray Diffraction

2000 ◽  
Vol 15 (6) ◽  
pp. 1349-1353 ◽  
Author(s):  
D. Sriram ◽  
R. L. Snyder ◽  
V. R. W. Amarakoon
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Barium Hexaferrite ◽  
X Ray Diffraction ◽  
Thermal Expansion Data ◽  
X Ray ◽  
Anisotropic Thermal Expansion ◽  
Short Period

Barium hexaferrite is a well-known ceramic permanent magnet and due to its high coercivity, remanence, and large uniaxial magnetic anisotropy, finds applications that compete with metallic magnets. Even though a number of the high-temperature properties of barium hexaferrite have been studied extensively, its anisotropic thermal expansion has not been reported so far. Dynamic high-temperature x-ray diffraction (HT-XRD) is one powerful method to obtain thermal expansion data for anisotropic polycrystalline materials in a very short period of time. In this paper the anisotropic nature of the thermal expansion coefficient of the barium hexaferrite phase is reported with the use of a dynamic HT-XRD setup. The thermal expansion coefficient (linear fit) was determined to be 8.36 × 10−6 K−1 along the a–b plane to 1.4 × 10−5 K−1 along the c axis between the temperature range of 293 to 1343 K.

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.

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

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