Electron charge density study of (Na1-xKx)NbO 3 in cubic structure

Chikako Moriyoshi; Jun Ichi Kato; Yoshihiro Terado; Satoshi Wada; Masaki Takata; Yoshihiro Kuroiwa

doi:10.1143/JJAP.47.7745

Electron charge density study of (Na_1-xK_x)NbO ₃ in cubic structure

Chikako Moriyoshi, Jun Ichi Kato, Yoshihiro Terado, Satoshi Wada, Masaki Takata, Yoshihiro Kuroiwa

SRIS - SR Core Research Division

Research output: Contribution to journal › Article › peer-review

15 Citations (Scopus)

Abstract

The electron charge density study by synchrotron-radiation powder diffraction has been performed for the cubic structure of (Na _1-xK_x)NbO₃ (NKN: 0 ≤ x ≤ 1) at 1000 K to investigate the atomic substitution effect on chemical bonding. Our precise analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the covalent bonding is formed on the Nb-O bond whereas the Na/K atoms are ionic in the entire composition range. The thermal motion of the Na ion in NaNbO₃ is fairly larger than that of the K ion in KNbO₃. The charge density distributions around the O atoms in NaNbO₃ are extended in the directions perpendicular to the Nb-O bond, which can be related to the rotational mode of the Nb-O₆ octahedron driving the antiferroic phase transition. No such anisotropy is clearly observed in KNbO₃ around the O atoms. These behaviors are closely related to the change in the tolerance of the perovskite structure caused by the atomic substitution.

Original language	English
Pages (from-to)	7745-7748
Number of pages	4
Journal	Japanese Journal of Applied Physics
Volume	47
Issue number	9 PART 2
DOIs	https://doi.org/10.1143/JJAP.47.7745
Publication status	Published - 2008 Sept 19

Keywords

Charge density
KNbO
Maximum entropy method
NKN
NaNbO
Perovskite
Powder diffraction
Synchrotron radiation
Thermal motion
Tolerance factor

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title = "Electron charge density study of (Na1-xKx)NbO 3 in cubic structure",

abstract = "The electron charge density study by synchrotron-radiation powder diffraction has been performed for the cubic structure of (Na 1-xKx)NbO3 (NKN: 0 ≤ x ≤ 1) at 1000 K to investigate the atomic substitution effect on chemical bonding. Our precise analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the covalent bonding is formed on the Nb-O bond whereas the Na/K atoms are ionic in the entire composition range. The thermal motion of the Na ion in NaNbO3 is fairly larger than that of the K ion in KNbO3. The charge density distributions around the O atoms in NaNbO3 are extended in the directions perpendicular to the Nb-O bond, which can be related to the rotational mode of the Nb-O6 octahedron driving the antiferroic phase transition. No such anisotropy is clearly observed in KNbO3 around the O atoms. These behaviors are closely related to the change in the tolerance of the perovskite structure caused by the atomic substitution.",

keywords = "Charge density, KNbO, Maximum entropy method, NKN, NaNbO, Perovskite, Powder diffraction, Synchrotron radiation, Thermal motion, Tolerance factor",

author = "Chikako Moriyoshi and Kato, {Jun Ichi} and Yoshihiro Terado and Satoshi Wada and Masaki Takata and Yoshihiro Kuroiwa",

year = "2008",

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doi = "10.1143/JJAP.47.7745",

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T1 - Electron charge density study of (Na1-xKx)NbO 3 in cubic structure

AU - Moriyoshi, Chikako

AU - Kato, Jun Ichi

AU - Terado, Yoshihiro

AU - Wada, Satoshi

AU - Takata, Masaki

AU - Kuroiwa, Yoshihiro

PY - 2008/9/19

Y1 - 2008/9/19

N2 - The electron charge density study by synchrotron-radiation powder diffraction has been performed for the cubic structure of (Na 1-xKx)NbO3 (NKN: 0 ≤ x ≤ 1) at 1000 K to investigate the atomic substitution effect on chemical bonding. Our precise analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the covalent bonding is formed on the Nb-O bond whereas the Na/K atoms are ionic in the entire composition range. The thermal motion of the Na ion in NaNbO3 is fairly larger than that of the K ion in KNbO3. The charge density distributions around the O atoms in NaNbO3 are extended in the directions perpendicular to the Nb-O bond, which can be related to the rotational mode of the Nb-O6 octahedron driving the antiferroic phase transition. No such anisotropy is clearly observed in KNbO3 around the O atoms. These behaviors are closely related to the change in the tolerance of the perovskite structure caused by the atomic substitution.

AB - The electron charge density study by synchrotron-radiation powder diffraction has been performed for the cubic structure of (Na 1-xKx)NbO3 (NKN: 0 ≤ x ≤ 1) at 1000 K to investigate the atomic substitution effect on chemical bonding. Our precise analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the covalent bonding is formed on the Nb-O bond whereas the Na/K atoms are ionic in the entire composition range. The thermal motion of the Na ion in NaNbO3 is fairly larger than that of the K ion in KNbO3. The charge density distributions around the O atoms in NaNbO3 are extended in the directions perpendicular to the Nb-O bond, which can be related to the rotational mode of the Nb-O6 octahedron driving the antiferroic phase transition. No such anisotropy is clearly observed in KNbO3 around the O atoms. These behaviors are closely related to the change in the tolerance of the perovskite structure caused by the atomic substitution.

KW - Charge density

KW - KNbO

KW - Maximum entropy method

KW - NKN

KW - NaNbO

KW - Perovskite

KW - Powder diffraction

KW - Synchrotron radiation

KW - Thermal motion

KW - Tolerance factor

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Electron charge density study of (Na_1-xK_x)NbO ₃ in cubic structure

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