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Phase transitions and ferroelectricity in NaSb 3 F 10
Author(s) -
Christie R. J.,
Wu P. K.,
Photinos P.,
Abrahams S. C.
Publication year - 2009
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889808036182
Subject(s) - ferroelectricity , dielectric , phase transition , pyroelectricity , materials science , phase (matter) , hysteresis , supergroup , crystallography , permittivity , condensed matter physics , analytical chemistry (journal) , nuclear magnetic resonance , chemistry , physics , optoelectronics , organic chemistry , geochemistry , chromatography , geology
Atomic coordinate analysis allows materials with appropriate but previously unrecognized dielectric properties to be predicted as new ferroelectrics if their crystal structure is known. An earlier such prediction that NaSb 3 F 10 is ferroelectric is confirmed herein without ambiguity. Its spontaneous polarization P s is found to exhibit reproducible dielectric hysteresis at room temperature, with P s ≃ 60 µC m −2 , under the application of a field of 0.3 MV m −1 or greater. The pyroelectric coefficient 〈 p 〉 = 17 (5) µC m −2 K −1 at 298 K. NaSb 3 F 10 undergoes a phase transition at T C ≃ 461 K, on correction for thermal hysteresis, with entropy change Δ S = 5.7 (3) J mol −1 K −1 . The colorless crystals melt at T m ≃ 515 K and decompose above ∼600 K. The thermal hysteresis of ∼35 K in T C , on heating and cooling at 5–25 K min −1 , is typical of first‐order phase transitions. The space group in ferroelectric phase III is P 6 3 , and that in phase II is predicted to be P 6 3 22, a nonpolar supergroup of P 6 3 ; the supergroup expected in the prototypic nonferroic phase I is P 6 3 / mmc . The space group of phase III is not a direct subgroup of phase I. The dielectric permittivity ɛ′ at 1 kHz increases over an order of magnitude between 300 K and a major inflection at T C , continuing to increase steadily thereafter to T m .