Synchrotron x-ray powder diffraction measurements have been performed on unpoled ceramic samples of $(1\ensuremath{-}x)\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}x{\mathrm{PbTiO}}_{3}$ (PMN-xPT) with $30%l~xl~39%$ as a function of temperature around the morphotropic phase boundary, which is the line separating the rhombohedral and tetragonal phases in the phase diagram. The experiments have revealed very interesting features previously unknown in this or related systems. The sharp and well-defined diffraction profiles observed at high and intermediate temperatures in the cubic and tetragonal phases, respectively, are in contrast to the broad features encountered at low temperatures. These peculiar characteristics, which are associated with the monoclinic phase of ${\mathrm{M}}_{C}$-type previously reported by Kiat et al. [Phys. Rev. B 65, 064106 (2000)] and Singh and Pandey [J. Phys. Condens Matter 13, L931 (2001)], can only be interpreted as multiple coexisting structures with ${\mathrm{M}}_{C}$ as the major component. An analysis of the diffraction profiles has allowed us to properly characterize the PMN-xPT phase diagram and to determine the stability region of the monoclinic phase, which extends from $x=31%$ to $x=37%$ at 20 K. The complex lansdcape of observed phases points to an energy balance between the different PMN-xPT phases which is intrinsically much more delicate than that of related systems such as ${\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ or $(1\ensuremath{-}x)\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{1/3}){\mathrm{O}}_{3}\ensuremath{-}x{\mathrm{PbTiO}}_{3}.$ These observations are in good accord with an optical study of $x=33%$ by Xu et al. [Phys. Rev. B 64, 020102 (2001)], who observed monoclinic domains with several different polar directions coexisting with rhombohedral domains, in the same single crystal.

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Phase diagram of the ferroelectric relaxor (1-x)PbMg1/3Nb2/3O3-xPbTiO3

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg1/3Nb2/3)O3-PbTiO3, Sr0.53Ba0.47Nb2O6, and (N...

Templated Grain Growth of Textured Piezoelectric Ceramics

Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.

A review of the recent advances in the understanding of piezoelectricity in lead oxide solid solutions is presented, giving special attention to the structural aspects. It has now become clear that the very high electromechanical response in these materials is directly related to the existence of low symmetry monoclinic phases.

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Structure and high-piezoelectricity in lead oxide solid solutions

We report on the observation of an orthorhombic ferroelectric phase in 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 single crystals, whose polarization is along 〈011〉 direction and stability can be altered by poling conditions. We studied the piezoelectric properties on poled 〈011〉 crystals, in both monodomain and polydomain states, and found that the piezoelectric d32 coefficient, which is the piezoelectric response in perpendicular to the poling direction, is positive in both cases. Based on the phenomenological theory, we show that this is possible in a crystal with the electrostrictive coefficients Q11>Q44–Q12.

D. Viehland

Papers

Phase transitional behavior and piezoelectric properties of the orthorhombic phase of Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals