Synthesis of novel compounds with cation ordered fluorite and α-PbO2 related structures by oxidation of Sn2Nb 2O7 pyrochlore

Takahisa Omata; Masao Kita; Shinya Otsuka-Yao-Matsuo; Motomi Katada

doi:10.1016/j.jallcom.2003.08.090

Synthesis of novel compounds with cation ordered fluorite and α-PbO₂ related structures by oxidation of Sn₂Nb ₂O₇ pyrochlore

Takahisa Omata, Masao Kita, Shinya Otsuka-Yao-Matsuo, Motomi Katada

Research output: Contribution to journal › Article

4 Citations (Scopus)

Abstract

Sn(II)_1.2(Nb(V)_1.6Sn(IV)_0.4)O₆ pyrochlore precursor was oxidized at temperature of the range 573-973K in 1% O₂/Ar and O₂ gases for various periods of time. Two kinds of novel metastable phases with a composition of Sn(IV)_0.6(Nb(V) _0.8Sn(IV)_0.2)O_3.6 could be synthesized. Further, the other novel metastable phase with the same composition was found as a phase contained. One of the metastable phases was the cubic κ-CeZrO₄ related-type possessing the fluorite-related structure, which was formed by the cation diffusionless insertion of the oxygen atom into original oxygen vacant site of the pyrochlore-type structure. Another was an orthorhombic α-PbO₂ related-type possessing a cation ordered arrangement unlike a well known NiWO₄ structure. The other was the rutile related-type possessing a cation ordered arrangement. Appearance of the two latter metastable phases could be attributed to the displacement of the oxygen stacking in the κ-CeZrO₄ related-type phase without cation redistributions. The appearance mechanisms were analogous to the well known transformations for AX₂ compounds among rutile-type, α-PbO₂-type, and fluorite-type phases under high pressure and its release. The dependence of the appearance of these novel metastable phases on oxygen partial pressure and temperature has been discussed in terms of the driving forces and energy barriers for reactions.

Original language	English
Pages (from-to)	80-89
Number of pages	10
Journal	Journal of Alloys and Compounds
Volume	370
Issue number	1-2
DOIs	https://doi.org/10.1016/j.jallcom.2003.08.090
Publication status	Published - 2004 May 12
Externally published	Yes

Keywords

Crystal growth
X-ray diffraction

ASJC Scopus subject areas

Mechanics of Materials
Mechanical Engineering
Metals and Alloys
Materials Chemistry

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Omata, T., Kita, M., Otsuka-Yao-Matsuo, S., & Katada, M. (2004). Synthesis of novel compounds with cation ordered fluorite and α-PbO₂ related structures by oxidation of Sn₂Nb ₂O₇ pyrochlore. Journal of Alloys and Compounds, 370(1-2), 80-89. https://doi.org/10.1016/j.jallcom.2003.08.090

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title = "Synthesis of novel compounds with cation ordered fluorite and α-PbO2 related structures by oxidation of Sn2Nb 2O7 pyrochlore",

abstract = "Sn(II)1.2(Nb(V)1.6Sn(IV)0.4)O6 pyrochlore precursor was oxidized at temperature of the range 573-973K in 1% O2/Ar and O2 gases for various periods of time. Two kinds of novel metastable phases with a composition of Sn(IV)0.6(Nb(V) 0.8Sn(IV)0.2)O3.6 could be synthesized. Further, the other novel metastable phase with the same composition was found as a phase contained. One of the metastable phases was the cubic κ-CeZrO4 related-type possessing the fluorite-related structure, which was formed by the cation diffusionless insertion of the oxygen atom into original oxygen vacant site of the pyrochlore-type structure. Another was an orthorhombic α-PbO2 related-type possessing a cation ordered arrangement unlike a well known NiWO4 structure. The other was the rutile related-type possessing a cation ordered arrangement. Appearance of the two latter metastable phases could be attributed to the displacement of the oxygen stacking in the κ-CeZrO4 related-type phase without cation redistributions. The appearance mechanisms were analogous to the well known transformations for AX2 compounds among rutile-type, α-PbO2-type, and fluorite-type phases under high pressure and its release. The dependence of the appearance of these novel metastable phases on oxygen partial pressure and temperature has been discussed in terms of the driving forces and energy barriers for reactions.",

keywords = "Crystal growth, X-ray diffraction",

author = "Takahisa Omata and Masao Kita and Shinya Otsuka-Yao-Matsuo and Motomi Katada",

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doi = "10.1016/j.jallcom.2003.08.090",

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T1 - Synthesis of novel compounds with cation ordered fluorite and α-PbO2 related structures by oxidation of Sn2Nb 2O7 pyrochlore

AU - Omata, Takahisa

AU - Kita, Masao

AU - Otsuka-Yao-Matsuo, Shinya

AU - Katada, Motomi

PY - 2004/5/12

Y1 - 2004/5/12

N2 - Sn(II)1.2(Nb(V)1.6Sn(IV)0.4)O6 pyrochlore precursor was oxidized at temperature of the range 573-973K in 1% O2/Ar and O2 gases for various periods of time. Two kinds of novel metastable phases with a composition of Sn(IV)0.6(Nb(V) 0.8Sn(IV)0.2)O3.6 could be synthesized. Further, the other novel metastable phase with the same composition was found as a phase contained. One of the metastable phases was the cubic κ-CeZrO4 related-type possessing the fluorite-related structure, which was formed by the cation diffusionless insertion of the oxygen atom into original oxygen vacant site of the pyrochlore-type structure. Another was an orthorhombic α-PbO2 related-type possessing a cation ordered arrangement unlike a well known NiWO4 structure. The other was the rutile related-type possessing a cation ordered arrangement. Appearance of the two latter metastable phases could be attributed to the displacement of the oxygen stacking in the κ-CeZrO4 related-type phase without cation redistributions. The appearance mechanisms were analogous to the well known transformations for AX2 compounds among rutile-type, α-PbO2-type, and fluorite-type phases under high pressure and its release. The dependence of the appearance of these novel metastable phases on oxygen partial pressure and temperature has been discussed in terms of the driving forces and energy barriers for reactions.

AB - Sn(II)1.2(Nb(V)1.6Sn(IV)0.4)O6 pyrochlore precursor was oxidized at temperature of the range 573-973K in 1% O2/Ar and O2 gases for various periods of time. Two kinds of novel metastable phases with a composition of Sn(IV)0.6(Nb(V) 0.8Sn(IV)0.2)O3.6 could be synthesized. Further, the other novel metastable phase with the same composition was found as a phase contained. One of the metastable phases was the cubic κ-CeZrO4 related-type possessing the fluorite-related structure, which was formed by the cation diffusionless insertion of the oxygen atom into original oxygen vacant site of the pyrochlore-type structure. Another was an orthorhombic α-PbO2 related-type possessing a cation ordered arrangement unlike a well known NiWO4 structure. The other was the rutile related-type possessing a cation ordered arrangement. Appearance of the two latter metastable phases could be attributed to the displacement of the oxygen stacking in the κ-CeZrO4 related-type phase without cation redistributions. The appearance mechanisms were analogous to the well known transformations for AX2 compounds among rutile-type, α-PbO2-type, and fluorite-type phases under high pressure and its release. The dependence of the appearance of these novel metastable phases on oxygen partial pressure and temperature has been discussed in terms of the driving forces and energy barriers for reactions.

KW - Crystal growth

KW - X-ray diffraction

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