Levin, I. ; Reaney, I. M. ; Anton, Eva-Maria ; Jo, Wook ; Rödel, Jürgen ; Pokorny, J. ; Schmitt, L. A. ; Kleebe, Hans-Joachim ; Hinterstein, Manuel ; Jones, J. L. (2013)
Local structure, pseudosymmetry, and phase transitions in Na1/2Bi1/2TiO3–K1/2Bi1/2TiO3 ceramics.
In: Physical Review B, 87 (2)
doi: 10.1103/PhysRevB.87.024113
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
The structural behavior of ceramic solid solutions (1−x)Na1/2Bi1/2TiO3–xK1/2Bi1/2TiO3 (NBT-KBT) was studied using high-resolution powder diffraction and transmission electron microscopy. A temperature-independent morphotropic phase boundary (MPB) separating NBT-like pseudorhombohedral (R) and KBT-like pseudotetragonal (T) phases was observed at x ≈ 0.2. For x<0.2, both local and average room-temperature structures are similar to those in NBT. Simultaneous long-range antiphase and short-range in-phase octahedral rotations average, resulting in effective antiphase a−a−c− tilting, which yields monoclinic symmetry when probed by x-ray diffraction (XRD). For these compositions, polar ordering is coupled to antiphase octahedral rotations so that tilting and ferroelectric (FE) domains coincide. Compositions with x>0.2 exhibit a tetragonal-like distortion; however, complex splitting of reflections in XRD patterns suggests that the actual symmetry is lower than tetragonal. For 0.2≤x≤0.5, in-phase octahedral tilting a0b+a0 (or a+b0b0) is present but confined to the nanoscale, while for x>0.5 the structure becomes untilted. In-phase tilting evolves above the ferroelectric transition and occurs around a nonpolar (a or b) axis of the average T structure. The onset of polar order has no significant effect on the coherence length of in-phase tilting, which suggests only weak coupling between the two phenomena. The average symmetry of the T phase is determined by the effective symmetry (Imm2) of assemblages of coherent in-phase tilted nanodomains. Near the MPB, the coexistence of extended R- and T-like regions is observed, but lattice distortions within each phase are small, yielding narrow peaks with a pseudocubic appearance in XRD. The temperature of the FE phase transition exhibits a minimum at the MPB. The structured diffuse scattering observed in electron diffraction patterns for all the compositions suggests that polar order in NBT-KBT solid solutions is modulated away from the average displacements refined using powder diffraction data.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2013 |
| Autor(en): | Levin, I. ; Reaney, I. M. ; Anton, Eva-Maria ; Jo, Wook ; Rödel, Jürgen ; Pokorny, J. ; Schmitt, L. A. ; Kleebe, Hans-Joachim ; Hinterstein, Manuel ; Jones, J. L. |
| Art des Eintrags: | Bibliographie |
| Titel: | Local structure, pseudosymmetry, and phase transitions in Na1/2Bi1/2TiO3–K1/2Bi1/2TiO3 ceramics |
| Sprache: | Englisch |
| Publikationsjahr: | 31 Januar 2013 |
| Verlag: | APS |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Physical Review B |
| Jahrgang/Volume einer Zeitschrift: | 87 |
| (Heft-)Nummer: | 2 |
| DOI: | 10.1103/PhysRevB.87.024113 |
| Kurzbeschreibung (Abstract): | The structural behavior of ceramic solid solutions (1−x)Na1/2Bi1/2TiO3–xK1/2Bi1/2TiO3 (NBT-KBT) was studied using high-resolution powder diffraction and transmission electron microscopy. A temperature-independent morphotropic phase boundary (MPB) separating NBT-like pseudorhombohedral (R) and KBT-like pseudotetragonal (T) phases was observed at x ≈ 0.2. For x<0.2, both local and average room-temperature structures are similar to those in NBT. Simultaneous long-range antiphase and short-range in-phase octahedral rotations average, resulting in effective antiphase a−a−c− tilting, which yields monoclinic symmetry when probed by x-ray diffraction (XRD). For these compositions, polar ordering is coupled to antiphase octahedral rotations so that tilting and ferroelectric (FE) domains coincide. Compositions with x>0.2 exhibit a tetragonal-like distortion; however, complex splitting of reflections in XRD patterns suggests that the actual symmetry is lower than tetragonal. For 0.2≤x≤0.5, in-phase octahedral tilting a0b+a0 (or a+b0b0) is present but confined to the nanoscale, while for x>0.5 the structure becomes untilted. In-phase tilting evolves above the ferroelectric transition and occurs around a nonpolar (a or b) axis of the average T structure. The onset of polar order has no significant effect on the coherence length of in-phase tilting, which suggests only weak coupling between the two phenomena. The average symmetry of the T phase is determined by the effective symmetry (Imm2) of assemblages of coherent in-phase tilted nanodomains. Near the MPB, the coexistence of extended R- and T-like regions is observed, but lattice distortions within each phase are small, yielding narrow peaks with a pseudocubic appearance in XRD. The temperature of the FE phase transition exhibits a minimum at the MPB. The structured diffuse scattering observed in electron diffraction patterns for all the compositions suggests that polar order in NBT-KBT solid solutions is modulated away from the average displacements refined using powder diffraction data. |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Geowissenschaften > Fachgebiet Geomaterialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Nichtmetallisch-Anorganische Werkstoffe |
| Hinterlegungsdatum: | 04 Feb 2013 08:39 |
| Letzte Änderung: | 16 Aug 2021 07:56 |
| PPN: | |
| Sponsoren: | This work benefited from the use of the Advanced Photon Source supported by the Department of Energy Office of Basic Energy Sciences under Contract No DE-AC02-06CH11357., J.J. acknowledges funding support from the US National Science Foundation under Award No. DMR-0746902 and the US Department of the Army under Contract No. W911NF-09-1-0435., Contributions by the Institute of Materials Science at Darmstadt were supported through the state center ADRIA. |
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