TY - JOUR
T1 - Structural Evolution in BiNbO4
AU - Yu, Chuying
AU - Viola, Giuseppe
AU - Zhang, Dou
AU - Stroscio, Zaira
AU - Hu, Zimeng
AU - Eskilla, Venkata Ramana
AU - Grasso, Salvatore
AU - Wilson, Rory M.
AU - Zhou, Kechao
AU - Bonini, Nicola
AU - Fortes, A. Dominic
AU - Abrahams, Isaac
AU - Yan, Haixue
N1 - Funding Information:
C.Y. and Z.H. gratefully acknowledge funding for Ph.D. scholarships from the China Scholarship Council. N.B. acknowledges the ARCHER UK National Supercomputing Service and the UK Materials and Molecular Modelling Hub for computational resources, which are partially funded by EPSRC (No. EP/P020194/1). V.R.E. acknowledges FCT, Portugal and I3N for Project No. 032-88-ARH/2018. The authors also acknowledge the STFC ISIS facility for beam-time, under No. RB1510218 (doi: 10.5286/ISIS.E.61004647 ) and thank the Pressure & Furnaces sample-environment team for assistance with the high-temperature measurements on HRPD.
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/6/21
Y1 - 2021/6/21
N2 - The sequence of transitions between different phases of BiNbO4 has been thoroughly investigated and clarified using thermal analysis, high-resolution neutron diffraction, and Raman spectroscopy. The theoretical optical phonon modes of the α-phase have been calculated. Based on thermoanalytical data supported by density functional theory (DFT) calculations, the β-phase is proposed to be metastable, while the α- and γ-phases are stable below and above 1040 °C, respectively. Accurate positional parameters for oxygen positions in the three main polymorphs (α, β, and γ) are presented and the structural relationships between these polymorphs are discussed. Even though no significant changes, only relaxation phenomena, are observed in the dielectric behavior of α-BiNbO4 below 1000 °C, evidence of two further subtle transitions at ∼350 and 600 °C is presented through careful analysis of structural parameters from variable temperature neutron diffraction measurements. Such phase variations are also evident in the phonon modes in Raman spectra and supported by changes in the thermoanalytical data. These subtle transitions may correspond to the previously proposed antiferroelectric to ferroelectric and ferroelectric to paraelectric phase transitions, respectively.
AB - The sequence of transitions between different phases of BiNbO4 has been thoroughly investigated and clarified using thermal analysis, high-resolution neutron diffraction, and Raman spectroscopy. The theoretical optical phonon modes of the α-phase have been calculated. Based on thermoanalytical data supported by density functional theory (DFT) calculations, the β-phase is proposed to be metastable, while the α- and γ-phases are stable below and above 1040 °C, respectively. Accurate positional parameters for oxygen positions in the three main polymorphs (α, β, and γ) are presented and the structural relationships between these polymorphs are discussed. Even though no significant changes, only relaxation phenomena, are observed in the dielectric behavior of α-BiNbO4 below 1000 °C, evidence of two further subtle transitions at ∼350 and 600 °C is presented through careful analysis of structural parameters from variable temperature neutron diffraction measurements. Such phase variations are also evident in the phonon modes in Raman spectra and supported by changes in the thermoanalytical data. These subtle transitions may correspond to the previously proposed antiferroelectric to ferroelectric and ferroelectric to paraelectric phase transitions, respectively.
UR - http://www.scopus.com/inward/record.url?scp=85108351277&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.1c00149
DO - 10.1021/acs.inorgchem.1c00149
M3 - Article
C2 - 34060816
AN - SCOPUS:85108351277
SN - 0020-1669
VL - 60
SP - 8507
EP - 8518
JO - INORGANIC CHEMISTRY
JF - INORGANIC CHEMISTRY
IS - 12
ER -