Anomalous phase in the relaxor ferroelectricPb(Zn1∕3Nb2∕3

Abstract

X-ray diffraction studies on a Pb(Zn 1/3 Nb 2/3 )O3 (PZN) single crystal sample show the presence of two different structures. An outer-layer exists in the outer most ∼ 10 to 50 µm of the crystal, and undergoes a structural phase transition at the Curie temperature TC ≈ 410 K. The inside phase is however, very different. The lattice inside the crystal maintains a cubic unit cell, while ferroelectric polarization develops below TC. The lattice parameter of the cubic unit cell remains virtually a constant, i.e., much less variations compared to that of a typical relaxor ferroelectric, in a wide temperature range of 15 K to 750 K. On the other hand, broadening of Bragg peaks and change of Bragg profile line-shapes in both longitudinal and transverse directions at TC clearly indicate a structural phase transition occurring.

Ground state monoclinic (Mb) phase in (110)c BiFeO3 epitaxial thin films

“…Similar effects have been observed in lead-based relaxors as well, where the near-surface region or "skin" layers have different structures than that of the bulk. [23][24][25][26] Our finding of the M b phase confirms that, in the ͑110͒ epitaxial film, the resulting polarization indeed lies in the ͑HHL͒ plane, in between the ͓110͔ and ͓111͔ directions. It is also relevant to note the presence of a slight offset of one of the domains with respect to the other along the ͑00L͒ in the mesh scans.…”

Damped soft phonons and diffuse scattering in40%Pb(Mg1∕3Nb2∕3)O3Stock1, Ellis2, Swainson3 et al. 2006Phys. Rev. BSelf Cite703551View full textAdd to dashboardCite

“…In PMN and PZN, the unit cell remains cubic in shape at all temperatures, though PZN has been found to have a near surface region where a structural transition is observed. 3,28 With increasing PT doping, the bulk unit cell in PMN does eventually undergo a structural transition, though PMN-10PT has been found to have an anomalous near surface layer similar in nature to that observed in PZN. the second ͑denoted as the high-temperature diffuse component͒ is not temperature dependent and present at the highest temperatures measured.…”

Dynamic origin of the morphotropic phase boundary: Soft modes and phase instability in0.68Pb(Mg1/3Nb2/3Cao1, Stock2, Xu3 et al. 2008Phys. Rev. BSelf Cite262150View full textAdd to dashboardCite

“…Second, the temperature at which the soft mode begins to recover is almost identical for PMN and PMN-0.32PT, even though PMN-0.32PT exhibits two well-defined structural phase transitions and no structural transition has been unambiguously identified in the bulk of PMN ͑in either zero or nonzero applied electric field͒ using neutron or x-ray diffraction techniques. [36][37][38][39][40] Third, the soft-mode recovery and the C → T phase transition occur at about the same temperature in both PMN-0.32PT and PMN-0.60PT, with the transition temperature T C being higher in PMN-0.60PT. Together these results suggest that the MPB defines a PT concentration where the structural transition temperature T C matches the temperature at which the soft mode recovers.…”