Morphotropic phase boundary of heterovalent perovskite solid solutions: Experimental and theoretical investigation of PbSc{sub 1/2}Nb{sub 1/2}O{sub 3}-PbTiO{sub 3}
- Laboratoire Structures, Proprietes et Modelisation des Solides, Ecole Centrale Paris, CNRS-UMR8580, Grande Voie des Vignes 92295, Chatenay-Malabry Cedex (France)
X-ray and neutron diffraction techniques are combined with first-principles-based simulations to derive and understand the structural properties of Pb(Sc,Nb,Ti)O{sub 3} (PSN-PT) near its morphotropic phase boundary (MPB). An analysis of our measurements yields, at room and low temperatures, an overall tetragonal T--monoclinic M{sub C}--monoclinic M{sub B}--rhombohedral R path (when adopting the notations of Vanderbilt and Cohen, Phys. Rev. B 63, 94108 (2001) for the monoclinic phases) as the Ti composition decreases across the MPB. A composition- and temperature-dependent significant mixing between some of these phases is also measured and reported here. The overall T-M{sub C}-M{sub B}-R path, which has also been proposed for Pb(Mg,Nb,Ti)O{sub 3} [A. K. Singh and D. Pandey, Phys. Rev. B 67, 64102 (2003)] is rather complex since it involves a change in the polarization path: this polarization first rotates in a (100) plane for the T-M{sub C} part of the path and then in a (1-10) plane for the M{sub B}-R part of the path. Moreover, a comparison between these measurements and first-principles-based calculations raises the possibility that this complex path, and the associated M{sub C} and M{sub B} phases, can only occur if the samples exhibit a deviation from a perfectly homogeneous and disordered situation, e.g. possess nanoscale chemically-ordered regions. If not, homogeneously disordered PSN-PT is predicted to exhibit at low temperature the same polarization path as Pb(Zr,Ti)O{sub 3}, that is T-monoclinic M{sub A}-R which involves a 'single' polarization rotation in a (1-10) plane. Nanoscale inhomogeneity may thus play a key role on the macroscopic properties of PSN-PT, in particular, and of other heterovalent complex solid solutions, in general, near their MPB.
- OSTI ID:
- 20666236
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 10 Vol. 71; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
LEAD COMPOUNDS
MONOCLINIC LATTICES
NANOSTRUCTURES
NEUTRON DIFFRACTION
NIOBIUM COMPOUNDS
PEROVSKITE
PHASE TRANSFORMATIONS
POLARIZATION
SCANDIUM COMPOUNDS
SIMULATION
SOLID SOLUTIONS
TETRAGONAL LATTICES
TITANATES
TRIGONAL LATTICES
X-RAY DIFFRACTION