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

ABSTRACT: 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 and twice each, respectively, in perovskite crystallography, in each case in compositions prepared at high pressure.

SUBMITTER: Dixon CAL

PROVIDER: S-EPMC5414396 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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

Dixon Charlotte A L CAL McNulty Jason A JA Huband Steven S Thomas Pamela A PA Lightfoot Philip P

IUCrJ 20170308 Pt 3

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- ...[more]

PMID: 28512569

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