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Noguchi, Yuji*; Aso, Seiyu*; Oyama, Kenji*; Ishigaki, Toru*; Yoneda, Yasuhiro; Matsuo, Hiroki*
Physical Review B, 111(21), p.214113_1 - 214113_13, 2025/06
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)We explore the electronic structure of high-quality bismuth sodium titanate (Bi
NaTiO
) powders through a comprehensive approach combining the maximum entropy method (MEM)/Rietveld analysis of synchrotron radiation X-ray diffraction data collected at 200 K with density functional theory (DFT) calculations. We conclude that the covalent Bi-O bond and the resultant ferroelectricity stem primarily from the Bi-6p-O3-2p orbital interaction mediated through Ti-3d.
phases in undoped and Ca-modified sodium niobatesAso, Seiyu*; Matsuo, Hiroki*; Yoneda, Yasuhiro; Morikawa, Daisuke*; Tsuda, Kenji*; Oyama, Kenji*; Ishigaki, Toru*; Noguchi, Yuji*
Physical Review B, 111(17), p.174114_1 - 174114_12, 2025/05
Times Cited Count：1 Percentile：64.20(Materials Science, Multidisciplinary)We investigate the crystal structures, phase transitions, and phase stability of undoped and Ca-modified NaNbO
through a combined analysis of high-resolution synchrotron radiation X-ray and neutron diffraction, convergent-beam electron diffraction, and density functional theory (DFT) calculations. It is demonstrated that the antiferroelectric (AFE)- phase is stabilized over a wide temperature range of 200 to 800 K by Ca modification, and that the NaNbO is stabilized by temperature-driven isostatic pressure accompanied by lattice expansion, whereas the Ca-modified NaNbO is induced by composition-induced chemical pressure along with lattice shrinkage.
Aso, Seiyu*; Yoneda, Yasuhiro; Matsuo, Hiroki*; Noguchi, Yuji*
no journal, ,
We have attempted to introduce positive chemical pressure into NaNbO by replacing Na
with a small Ca
. The superlattice reflections originating from the antiferroelectric P phase appeared both before and after the application of an electric field, which confirmed that a reversible electric-field-induced phase transition was achieved.
Yoneda, Yasuhiro; Kobayashi, Toru; Tsuji, Takuya; Saito, Yuji; Matsumura, Daiju; Aso, Seiyu*; Noguchi, Yuji*
no journal, ,
no abstracts in English
in high-temperature phaseAso, Seiyu*; Matsuo, Hiroki*; Noguchi, Yuji*; Yoneda, Yasuhiro; Morikawa, Daisuke*; Tsuda, Kenji*
no journal, ,
Recently, higher energy storage density than that of typical ferroelectric BaTiO has been achieved in NaNbO-based antiferroelectrics by utilizing the electric-field-induced phase transition between the antiferroelectric (AFE) and ferroelectric (FE) phases. In this study, we attempted to identify the space group using synchrotron X-ray diffraction and convergent electron diffraction in order to elucidate the full picture of the phase transition behavior in NaNbO and Ca-doped NaNbO. On the other hand, the Ca-doped sample showed that the space group is Pnma, which is consistent with the results obtained by convergent electron diffraction measurements.
