Unprecedented phase transition sequence in the perovskite Li0.2Na0.8NbO3

Charlotte A. L. Dixon; Jason A. McNulty; Steven Huband; Pamela A. Thomas; Philip Lightfoot

doi:10.1107/S2052252517002226

Unprecedented phase transition sequence in the perovskite Li_0.2Na_0.8NbO₃

Charlotte A. L. Dixon, Jason A. McNulty, Steven Huband, Pamela A. Thomas, Philip Lightfoot

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

Abstract

We demonstrate the existence of a novel phase transition sequence in the perovskite Li_0.2Na_0.8NbO₃ at elevated temperature. The rare Glazer tilt system, a⁺a⁺c^-, is observed in both polar and centrosymmetric polymorphs.

The perovskite Li_0.2Na_0.8NbO₃ is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P4₂mc) in the region 150 – 300 °C; these two phases correspond to Glazer tilt systems a^-a^-a^- and a⁺a⁺c^-, respectively. At 500 °C a ferroelectric – paraelectric transition takes place from P4₂mc to P4₂/nmc, retaining the a⁺a⁺c^- tilt. Transformation to a single-tilt system, a⁰a⁰c⁺ (space group P4/mbm), occurs at 750 °C, with the final transition to the aristotype cubic phase at 850 °C. The P4₂mc and P4₂/nmc phases have each been seen only once previously in perovskite crystallography, in both cases in compositions prepared at high pressure.

Original language	English
Pages (from-to)	215-222
Journal	International Union of Crystallography Journal (IUCrJ)
Volume	4
Issue number	3
Early online date	8 Mar 2017
DOIs	https://doi.org/10.1107/S2052252517002226
Publication status	Published - May 2017

Keywords

Perovskite
Ferroelectric
Powder neutron diffraction

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Final published version, 1.06 MBLicence: CC BY

Philip Lightfoot
- plst-andrews.acuk
- School of Chemistry - Emeritus Professor
- EaSTCHEM
Person: Emeritus Professor

Data underpinning article "Unprecedented phase transition sequence in the perovskite Li0.2Na0.8NbO3 "
Dixon, C. A. L. (Creator), McNulty, J. A. (Creator), Huband, S. (Creator), Thomas, P. A. (Creator) & Lightfoot, P. (Creator), University of St Andrews, 27 Mar 2017
DOI: 10.17630/c97a6cc7-05e8-4f3a-b881-0ee334dee69d
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title = "Unprecedented phase transition sequence in the perovskite Li0.2Na0.8NbO3",

abstract = "We demonstrate the existence of a novel phase transition sequence in the perovskite Li0.2Na0.8NbO3 at elevated temperature. The rare Glazer tilt system, a+a+c-, is observed in both polar and centrosymmetric polymorphs.The perovskite Li0.2Na0.8NbO3 is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P42mc) in the region 150 – 300 °C; these two phases correspond to Glazer tilt systems a-a-a- and a+a+c-, respectively. At 500 °C a ferroelectric – paraelectric transition takes place from P42mc to P42/nmc, retaining the a+a+c- tilt. Transformation to a single-tilt system, a0a0c+ (space group P4/mbm), occurs at 750 °C, with the final transition to the aristotype cubic phase at 850 °C. The P42mc and P42/nmc phases have each been seen only once previously in perovskite crystallography, in both cases in compositions prepared at high pressure.",

keywords = "Perovskite, Ferroelectric, Powder neutron diffraction",

author = "Dixon, {Charlotte A. L.} and McNulty, {Jason A.} and Steven Huband and Thomas, {Pamela A.} and Philip Lightfoot",

note = "Funding for this research was provided by: EPSRC (award No. EP/L505079/1).",

year = "2017",

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language = "English",

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TY - JOUR

T1 - Unprecedented phase transition sequence in the perovskite Li0.2Na0.8NbO3

AU - Dixon, Charlotte A. L.

AU - McNulty, Jason A.

AU - Huband, Steven

AU - Thomas, Pamela A.

AU - Lightfoot, Philip

N1 - Funding for this research was provided by: EPSRC (award No. EP/L505079/1).

PY - 2017/5

Y1 - 2017/5

N2 - We demonstrate the existence of a novel phase transition sequence in the perovskite Li0.2Na0.8NbO3 at elevated temperature. The rare Glazer tilt system, a+a+c-, is observed in both polar and centrosymmetric polymorphs.The perovskite Li0.2Na0.8NbO3 is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P42mc) in the region 150 – 300 °C; these two phases correspond to Glazer tilt systems a-a-a- and a+a+c-, respectively. At 500 °C a ferroelectric – paraelectric transition takes place from P42mc to P42/nmc, retaining the a+a+c- tilt. Transformation to a single-tilt system, a0a0c+ (space group P4/mbm), occurs at 750 °C, with the final transition to the aristotype cubic phase at 850 °C. The P42mc and P42/nmc phases have each been seen only once previously in perovskite crystallography, in both cases in compositions prepared at high pressure.

AB - We demonstrate the existence of a novel phase transition sequence in the perovskite Li0.2Na0.8NbO3 at elevated temperature. The rare Glazer tilt system, a+a+c-, is observed in both polar and centrosymmetric polymorphs.The perovskite Li0.2Na0.8NbO3 is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P42mc) in the region 150 – 300 °C; these two phases correspond to Glazer tilt systems a-a-a- and a+a+c-, respectively. At 500 °C a ferroelectric – paraelectric transition takes place from P42mc to P42/nmc, retaining the a+a+c- tilt. Transformation to a single-tilt system, a0a0c+ (space group P4/mbm), occurs at 750 °C, with the final transition to the aristotype cubic phase at 850 °C. The P42mc and P42/nmc phases have each been seen only once previously in perovskite crystallography, in both cases in compositions prepared at high pressure.

KW - Perovskite

KW - Ferroelectric

KW - Powder neutron diffraction

U2 - 10.1107/S2052252517002226

DO - 10.1107/S2052252517002226

M3 - Article

SN - 2052-2525

VL - 4

SP - 215

EP - 222

JO - International Union of Crystallography Journal (IUCrJ)

JF - International Union of Crystallography Journal (IUCrJ)

IS - 3

ER -

Unprecedented phase transition sequence in the perovskite Li0.2Na0.8NbO3

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Unprecedented phase transition sequence in the perovskite Li_0.2Na_0.8NbO₃