Compression mechanisms of ferroelectric PbTiO via high pressure neutron scattering.

Switchable atomic displacements generate electric dipole moments in ferroelectric materials utilized in many contemporary devices. Lead titanate, a perovskite oxide with formula PbTiO, has been referred to as a textbook example of a prototype displacive ferroelectric and is a testing platform of widely used models of piezoelectric response of complex solid-solutions. PbTiO has been addressed by experimental and computational studies, often with apparently conflicting conclusions.

Raman Study of the Structural Distortion in the Ni1-xCoxTiO3 Solid Solution.

Raman spectra were collected on Ni1-xCoxTiO3 (0 ≤ x ≤ 1) ilmenite samples as a function of the temperature between 4 and 1200 K. An evident symmetry lowering from the prototype R3̅ symmetry is observed. The distortion was largest for the x = 0.

Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb(Zr0.80Ti0.20)O3 single crystal.

A single crystal of lead-zirconate-titanate, composition Pb(Zr0.80Ti0.20)O3, was studied by polarized-Raman scattering as a function of temperature.

Microstrain in tetragonal lead-zirconate-titanate: the effect of pressure on the ionic displacements.

Piezoelectric materials respond to external stimuli by adjusting atomic positions. In solid-solutions, the changes occurring in atomic scale are very complex since the short- and long-range order are different. Standard methods used in diffraction data analysis fail to model the short-range order accurately.

Pressure-induced reversal between thermal contraction and expansion in ferroelectric PbTiO3.

Materials with zero/near zero thermal expansion coefficients are technologically important for applications in thermal management and engineering. To date, this class of materials can only be produced by chemical routes, either by changing chemical compositions or by composting materials with positive and negative thermal expansion. Here, we report for the first time a physical route to achieve near zero thermal expansion through application of pressure.

The factors behind the morphotropic phase boundary in piezoelectric perovskites.

The best piezoelectric materials are solid solutions in the vicinity of the steep morphotropic phase boundary (MPB) separating rhombohedral and tetragonal phases in the composition-temperature plane. A classical example is the lead zirconate titanate [Pb(Zr(x)Ti(1-x))O(3), PZT] system, with x approximately 0.52, where the two phases are separated by a boundary extending from the lowest temperatures up to several hundred degrees.

Electronic energy band structure of the double perovskite Ba2MnWO6.

The electronic and magnetic structures of the double perovskite oxide Ba 2MnWO6 (BMW) were determined by employing the density functional theory within the generalized gradient approximation (GGA) + U approach. BMW is considered a prototype double perovskite due to its high degree of B-site ordering and is a good case study for making a comparison between computations and experiments. By adjusting the U-parameter, the electronic energy band structure and magnetic properties, which were consistent with the experimental results, were obtained.

Notes of the recent structural studies on lead zirconate titanate.

Atomic scale structure has a central importance for the understanding of functional properties of ferroelectrics. The X-ray and neutron diffraction studies used for the average symmetry determination of lead zirconate titanate [Pb(ZrxTi(1- x))O3, PZT] ceramics and powders are reviewed. The results obtained through two frequently used local probes, transmission electron microscopy (TEM) combined with electron diffraction (ED) and Raman scattering measurements, are summarized.

Pressure-induced phase transitions in PbTiO3: a query for the polarization rotation theory.

Our first-principles computations show that the ground state of PbTiO3 under hydrostatic pressure transforms discontinuously from P4mm to R3c at 9 GPa. Spontaneous polarization decreases with increasing pressure so that the R3c phase transforms to the centrosymmetric Rc phase at around 27 GPa. The first-order phase transition between the tetragonal and rhombohedral phases is exceptional since there is no evidence for a bridging phase.

Hydrothermal synthesis and characterization of nanorods of various titanates and titanium dioxide.

The formation process of titania based nanorods during hydrothermal synthesis starting from an amorphous TiO2.nH2O gel has been investigated. Sodium tri-titanate (Na2Ti3O7) particles with a rodlike morphology were prepared by a simple hydrothermal process in the presence of a concentrated NaOH aqueous solution.

Raman scattering studies of the Ba2MnWO6 and Sr2MnWO6 double perovskites.

Polycrystalline Ba2MnWO6 (BMW) and Sr2MnWO6 (SMW) samples were studied between 80 and 1200 K by Raman scattering spectroscopy. In the case of BMW (space group Fmm), four Raman active vibrational modes, predicted by factor group analysis, were identified. Raman scattering studies with different wavelengths revealed a resonant bands between 300 and 800 cm-1.

Neutron powder diffraction study of Pb(HfxTi1-x)O3 ceramics (0.10

The crystal symmetries of lead hafnate titanate (Pb(HfxTi1-x)O3, PHT) powders with 0.10 View Article and Find Full Text PDF