Uniaxial-stress induced phase transitions in [001]c-poled 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3

First-order, rhombohedral to orthorhombic, stress-induced phase transitions have been evidenced by bulk charge-stress measurements and X-ray diffraction derived lattice strain measurements in [001]c-poled PZN-4.5PT. The transitions are induced by uniaxial, compressive loads applied either along or perpendicular to the poling direction. In each case, they occur via rotation of the polar vector in the Cm monoclinic plane and the induced lattice strain is hysteretic yet reversible. Although no depoling is observed in the transverse mode, net depolarization is observed under longitudinal stress which is important for the use of [001]c-poled PZN-PT and PMN-PT single crystals in Tonpilz-type underwater projectors.Comment: To be published in Applied Physics Letters, 16 pages, 3 figure

Partial decoupling between strain and polarization in mono-oriented Pb(Zr0.2Ti0.8)O3 thin film

The structural evolution of epitaxial mono-oriented (i.e. with the c-axis perpendicular to the interface) ferroelectric Pb(Zr0.2,Ti0.8)O3 thin film has been investigated, using high resolution, temperature dependent, X-ray diffraction. The full set of lattice parameters was obtained, it allowed to estimate the variation of the polarization as a function of temperature, underlying the difference between the polarization-induced tetragonality and the elastic one. The temperature evolution of the misfit strain has been calculated and found to be in good agreement with the theoretical temperature-misfit strain phase diagramComment: 11 pages, 3 figure

Giant direct magnetoelectric effect in strained multiferroic heterostructures

The direct magnetoelectric (ME) effect mediated by lattice strains induced in a ferroelectric film by a ferromagnetic substrate is evaluated using first-principles-based calculations. To that end, the strain sensitivity of ferroelectric polarization and the film permittivity are calculated as a function of the in-plane biaxial strain for Pb(Zr0.52Ti0.48)O3 films under various depolarizing fields. It is found that the ME voltage coefficient varies nonmonotonically with this strain and may reach giant values exceeding 100 Vcm-1 Oe-1 over a strain range that can be controlled through the electrical boundary conditions.Comment: Accepted as a Rapid Communication by Phys.Rev.B (http://prb.aps.org/

Phase diagram of Pb(Zr,Ti)O3 solid solutions from first principles

A first-principles-derived scheme, that incorporates ferroelectric and antiferrodistortive degrees of freedom, is developed to study finite-temperature properties of PbZr1-xTixO3 solid solutions near its morphotropic phase boundary. The use of this numerical technique (i) resolves controversies about the monoclinic ground-state for some Ti compositions, (ii) leads to the discovery of an overlooked phase, and (iii) yields three multiphase points, that are each associated with four phases. Additional neutron diffraction measurements strongly support some of these predictions.Comment: 10 pages, 2 figure

Generalized relation between electromechanical responses at fixed voltage and fixed electric field

We present a general relation between the electromechanical couplings of infinitesimal strain and electric field to arbitrary order, measured at fixed voltage and at fixed electric field. We show that the improper response at fixed field can be written as the strain derivative of the $n^{\text{th}}$ order susceptibility tensor, and the proper response at fixed voltage drop can be written as the response at fixed field plus corrections for dilations and 90$^{\circ}$ rotations induced by strain. Our theory correctly reproduces the proper piezoelectric response and we go beyond with the electrostrictive response. We present first-principles calculations of the improper electrostrictive response at fixed field, and illustrate how the correction is used to obtain the proper response at fixed voltage. This distinction is of high importance given the recent interest in giant electrostrictors exhibiting electromechanical responses as large as the piezoelectric ones.Comment: Accepted versio

Synthesis dependent characteristics of Sr1-xMnxTiO3 (x=0.03, 0.05, 0.07 and 0.09)

Sr1-xMnxTiO3 (where x = 0.03, 0.05, 0.07 and 0.09) was synthesized via different routes that include solid-state, oxalate precipitation and freeze drying. In oxalate precipitation technique, compositions corresponding to 3 and 5 mol % doping of Mn were monophasic whereas the higher compositions revealed the presence of the secondary phases such as MnO, Mn3O4 etc., as confirmed by high resolution X-ray diffraction (XRD) studies. The decomposition behavior of the precursors prepared using oxalate precipitation method corresponding to the above mentioned compositions was studied. Nanopowders of compositions pertaining to 5 to 9 mol % of Mn doping were obtained using freeze-drying technique. The average crystallite size of these nanopowders was found to be in the 35 to 65 nm range. The microstructural studies carried out on the sintered ceramics, fabricated using powders synthesized by different routes established the fine grained nature (< 1 microm) of the one obtained by freeze drying method. Raman scattering studies were carried out in order to complement the observations made from XRD regarding the phase purity. The dielectric properties of the ceramics obtained by different synthesis routes were studied in the 80 - 300 K temperature range at 100 kHz and the effect of grain size has been discussed.Comment: 38 pages, 4 tables, 13 figure

Original Reaction Sequence of Pb(Yb_1/2Nb_1/2)O₃-PbTiO₃:Consequences on dielectric properties and chemical order

International audienceThe solid solution [Pb(Yb 1/2 Nb 1/2)O 3 ] 1−x-[PbTiO 3 ] x was synthesized with í µí±¥ ≤ 60%, using several high-temperature techniques as well as room-temperature mechanosynthesis. The high-temperature synthesis reveals a reaction path involving the synthesis first of the end-members before the solid solution. The density and dielectric constant measured on the ceramics prepared from these powders indicate the crucial role of the synthesis technique in the subsequent properties. Mechanosynthesis results in ceramics with higher density and dielectric constant. Identical optimized sintering conditions were then applied to all investigated compositions and the resulting dielectric properties and chemical orders were compared. All polar orders (antiferroelectricity, ferroelectricity, and relaxor behavior) were evidenced. The 1 : 1 chemical order on the B-site of Pb(Yb 1/2 Nb 1/2)O 3 results in the formation of a double perovskite Pb 2 YbNbO 6 , and the superstructures in the X-ray diagrams signing the existence of this order persist up to 30% PbTiO 3. The underlying mechanism for substitution of Yb or Nb by Ti is presented

A new look at the temperature-dependent properties of the antiferroelectric model PbZrO3: an effective Hamiltonian study

A novel atomistic effective Hamiltonian scheme, incorporating an original and simple bilinear energetic coupling, is developed and used to investigate the temperature dependent physical properties of the prototype antiferroelectric PbZrO3 (PZO) system. This scheme reproduces very well the known experimental hallmarks of the complex Pbam orthorhombic phase at low temperatures and the cubic paraelectric state of Pm 3m symmetry at high temperatures. Unexpectedly, it further predicts a novel intermediate state also of Pbam symmetry, but in which anti-phase oxygen octahedral tiltings have vanished with respect to the Pbam ground state. Interestingly, such new state exhibits a large dielectric response and thermal expansion that remarkably agree with previous experimental observations and the x-ray experiments we performed. We also conducted direct first-principles calculations at 0K which further support such low energy phase. Within this fresh framework, a re-examination of the properties of PZO is thus called for.Comment: 21 pages, 4 figures. This paper is submitted to Physical Review

Structural transition in LaVO3/SrVO3 superlattices and its influence on transport properties

Measurements of the resistive properties and the lattice parameters of a (LaVO3)[6 unit cells]/(SrVO3)[1 unit cell] superlattice between 10K and room temperature are presented. A low temperature metallic phase compatible with a Fermi liquid behavior is evidenced. It disappears in the vicinity of a structural transition from a monoclinic to tetragonal phase, in which disorder seems to strongly influence the transport. Our results will enrich the understanding of the electronic properties of complex heterostructures.Comment: accepted in APL 201