Study on the phase behavior of BaEu2Mn2O7 through heat treatment of a single crystal

Kamegashira, Naoki; Meng, Jian; Fujita, Kouji; Satoh, Hiroyuki; Shishido, Toetsu; Nakajima, Kazuo

doi:10.1016/j.jallcom.2004.12.197

Cited by 8 publications

(6 citation statements)

References 18 publications

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“…However, the transformation temperature was lower than that of phase transition (277 • C) measured by DSC. 11 With increasing temperature, we found the phase transformation in the next step. The I4/mmm phase was stable in a narrow temperature region.…”

Section: Resultsmentioning

confidence: 82%

“…Then, a new phase III started to nucleate in the low-temperature phase matrix at 277 • C, and the temperature agreed with the DSC and electrical conductivity results. 10,11 The complex pattern (e) can be interpreted as a mixture of the low-temperature phase (d) and the high-temperature phase (f). At around 500 • C, the intensity of 1 1 0 reflection became very weak, which indicated that the low-temperature phase nearly disappeared in (f).…”

Section: Resultsmentioning

confidence: 99%

“…The phase transformations of the oxides have been investigated by high-temperature X-ray diffraction (XRD), electrical conductivity, and thermal analyses. 3,10,11 The transformation temperatures tend to increase with decreasing ionic radii of the Ln cations. 10 These results showed that the transformation occurring is the successive phase transition series common in perovskite-related families, whose symmetries are expected to change from lower to higher with increasing temperature.…”

Section: Introductionmentioning

confidence: 99%

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In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7

Nakano

Ishizawa

Kamegashira

2010

Journal of the European Ceramic Society

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7

Nakano

Ishizawa

Kamegashira

2010

Journal of the European Ceramic Society

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“…From the SAED patterns, phase III seems to have a close relation with the monoclinic B112/m structure that was observed in BaTb 2 Mn 2 O 7 upon annealing. 39) It is expected that one or more phase transitions occur at temperatures above 1023 K because the symmetry of phase III is still much lower than the F4/mmm assumed for the prototype.…”

Section: )mentioning

confidence: 99%

Microstructural evolution by in-situ TEM observations of oxides

Nakano

2011

J. Ceram. Soc. Japan

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In-situ observations using high-temperature transmission electron microscopy (TEM) is a promising technique for obtaining new findings and developing phenomenological theory for ceramic materials at high temperatures. By observing the changes in hydrothermal BaTiO 3 due to heating, we clarify the vanishing mechanism of internal pores and the mechanism of BaCO 3 phase generation/vanishing at high temperatures. Through observations of the grain growth of BaTiO 3 prepared by radio-frequency plasma chemical vapor deposition, we calculate the grain-boundary diffusion coefficient, which is an important parameter controlling the sinterability of ceramics. Observations of the shrinkage and disappearance of Ba 5 Nb 4 O 15 , as well as simulations, indicate that high energy and low diffusivity at the grain boundary make grains vanish while maintaining a truncated spherical shape. Finally, observations of the structural changes in layered perovskite BaLn 2 Mn 2 O 7 (Ln = Gd, Pr, Eu) reveal a first-order phase transition that has not been previously reported.

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“…20) We already reported the results of structure analysis for BaLn 2 Mn 2 O 7 compounds of some rare earths. [21][22][23][24] In this paper, we report the refined structures of BaTb 2 Mn 2 O 7 single crystal appeared by thermal treatments.…”

Section: Introductionmentioning

confidence: 99%

High Temperature Phase Behavior of BaTb2Mn2O7 by Thermal Treatment of Single Crystals

Satoh

Nara

Nakano

et al. 2014

Trans. Mat. Res. Soc. Japan

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In order to clarify complicated phase behaviors and to obtain a unified explanation in such sequential phase transitions, formation of three kinds of tetragonal phases with a fundamental structure (I4/mmm) and the superstructures (P4 2 /mnm and Ccmm) for BaTb 2 Mn 2 O 7 are mainly discussed in this study. Single crystal of this compound was also grown by Floating Zone method. The crystal structure was analyzed by four circle X-ray method. As grown single crystal showed the tetragonal phase with a superstructure with the lattice parameters of a x a x c (a and c are lattice parameters of fundamental tetragonal cell). Thermal anomalies were observed at 440 K and 740 K from DSC curve. When this as-grown specimen was annealed in purified argon atmosphere at 1373K for several days and quenched to room temperature, this phase changed into the fundamental tetragonal phase. On the one hand, When same specimen was annealed in purified argon atmosphere at 573 K for several days and slowly cooled to room temperature, phase changed into the orthorhombic space group Ccmm. As grown crystals have P4 2 /mnm type tetragonal phase within the middle temperature, Ccmm type orthorhombic phase at room temperature and I4/mmm type tetragonal phase at high temperature.

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Study on the phase behavior of BaEu2Mn2O7 through heat treatment of a single crystal

Cited by 8 publications

References 18 publications

In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7

In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7

Microstructural evolution by in-situ TEM observations of oxides

High Temperature Phase Behavior of BaTb<sub>2</sub>Mn<sub>2</sub>O<sub>7</sub> by Thermal Treatment of Single Crystals

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