Phase competition and effect of chemical ordering in ferroelectric relaxor PbSc.sub.0,5./sub.Nb.sub.0,5./sub.O.sub.3./sub. from first principles

0465878 - FZÚ 2017 RIV GB eng J - Článek v odborném periodiku
Pasciak, Marek - Welberry, T.R. - Hlinka, Jiří
Phase competition and effect of chemical ordering in ferroelectric relaxor PbSc_0,5Nb_0,5O₃ from first principles.
Phase Transitions. Roč. 89, č. 7-8 (2016), s. 777-784. ISSN 0141-1594. E-ISSN 1029-0338
Grant CEP: GA ČR GA15-04121S
Institucionální podpora: RVO:68378271
Klíčová slova: ferroelectric relaxor * soft modes * antiferroelectricity * first principles
Kód oboru RIV: BM - Fyzika pevných látek a magnetismus
Impakt faktor: 1.060, rok: 2016

We present results of first principles calculations for ferroelectric relaxor PbSc0.5Nb0.5O3. An ordered supercell with Sc and Nb atoms alternating in all directions (NaCl-like superstructure) has a ferroelectric ground state with R3 spacegroup. It is characterized by a tilt system a−a−a− as well as different sizes of adjacent oxygen octahedra. Analysis of phonon instabilities in cubic reveals similarity with an antiferroelectric PbZrO3. This is further confirmed by the fact that possibly antiferroelectric P21/b structure of PbSc0.5Nb0.5O3 (symmetry lowered from Pbam due to Sc/Nb superstructure) is energetically very close to the ground state. The ferroelectric order is shown to be less sensitive to deviations in the B-site distribution than the antiferroelectric one.
Trvalý link: http://hdl.handle.net/11104/0264357