Structure of the high-temperature phase of caesium nitrate - the importance of high-resolution data.

A single-crystal structure determination of the cubic phase of CsNO based on data collected at 439 K up to sinθ/λ = 0.995000 Å, i.e.

Disorder in Strontium Barium Niobate: Local Structure, Phonons, and Polarization Dynamics.

The main representative of the tetragonal tungsten bronze family, strontium barium niobate, has been recently studied by the scattering and spectroscopic techniques [diffuse scattering (DS), Raman, infrared, and high-frequency dielectric spectroscopies] to decipher the nature of its ferroelectric-relaxor transformation tuned by composition. DS revealed that mesoscopic range ordered correlations along the polar axis are presented in the crystal, being less organized in the relaxor compositions with higher Sr content. For these compositions, transverse polar correlations are found to be anisotropic.

Damage from Coexistence of Ferroelectric and Antiferroelectric Domains and Clustering of O Vacancies in PZT: An Elastic and Raman Study.

It is often suggested that oxygen vacancies (V O ) are involved in fatigue and pinning of domain walls in ferroelectric (FE) materials, but generally without definite evidence or models. Here the progress of damage induced by the coexistence of FE and antiferroelectric (AFE) domains in the absence of electric cycling is probed by monitoring the Young's modulus, which may undergo more than fourfold softenings without significant changes in the Raman spectra, but may end with the disaggregation of PZT with ∼5% Ti. At these compositions, the FE and AFE phases coexist at room temperature, as also observed with micro-Raman, and hence the observations are interpreted in terms of the aggregation of V O at the interfaces between FE and AFE domains, which are sources of internal electric and stress fields.

Laser-synthesized nanocrystalline, ferroelectric, bioactive BaTiO/Pt/FS for bone implants.

The goal of our study is to design BaTiO ferroelectric layers that will cover metal implants and provide improved osseointegration. We synthesized ferroelectric BaTiO layers on Pt/fused silica substrates, and we studied their physical and bio-properties. BaTiO and Pt layers were prepared using KrF excimer laser ablation at substrate temperature T in the range from 200°C to 750°C in vacuum or under oxygen pressure of 10 Pa, 15 Pa, and 20 Pa.

Fast polarization mechanisms in the uniaxial tungsten-bronze relaxor strontium barium niobate SBN-81.

The high-frequency dielectric response of the uniaxial strontium barium niobate crystals with 81% of Sr has been studied from 1 kHz to 30 THz along the polar c axis by means of several techniques (far infrared, time domain terahertz, high-frequency and low-frequency dielectric spectroscopies) in a wide temperature interval 20-600 K. Relaxor properties were observed in the complex dielectric response and four main excitations were ascertained below the phonon frequencies. These fast polarization mechanisms take place at THz, GHz and MHz ranges and show different temperature evolution.

PLD prepared bioactive BaTiO films on TiNb implants.

BaTiO (BTO) layers were deposited by pulsed laser deposition (PLD) on TiNb, Pt/TiNb, Si (100), and fused silica substrates using various deposition conditions. Polycrystalline BTO with sizes of crystallites in the range from 90nm to 160nm was obtained at elevated substrate temperatures of (600°C-700°C). With increasing deposition temperature above 700°C the formation of unwanted rutile phase prevented the growth of perovskite ferroelectric BTO.

Multiple soft-mode vibrations of lead zirconate.

Polarized Raman, IR, and time-domain THz spectroscopy of orthorhombic lead zirconate single crystals have yielded a comprehensive picture of temperature-dependent quasiharmonic frequencies of its low-frequency phonon modes. It is argued that these modes primarily involve vibrations of Pb ions and librations of oxygen octahedra. Their relation to phonon modes of the parent cubic phase is proposed.

Fermi resonance involving nonlinear dynamical couplings in Pb(Zr,Ti)O3 solid solutions.

We have used first-principles-based simulations and Raman scattering techniques to reveal a novel dynamical phenomenon in Pb(Zr,Ti)O(3) solid solutions: a Fermi resonance (FR) emerging from the nonlinear coupling between ferroelectric (FE) motions and tiltings of oxygen octahedra. This FR manifests itself as the doubling of a nominally single FE mode in a purely FE phase, when the resonant frequency of the FE mode is close to the first overtone of the tiltings. We show that the FR is the result of a nonlinear coupling that is proportional to the spontaneous polarization of the material and derive an analytical model that captures the essence of the effect.

Raman spectroscopic study of the uranyl sulphate mineral zippeite: low wavenumber and U-O stretching regions.

The uranyl sulphate mineral zippeite was studied by Raman spectroscopy. The phase purity of the sample was initially checked by X-ray powder diffraction and its chemical composition was defined by electron microprobe (wavelength dispersive spectroscopy, WDS) analysis. The Raman spectroscopy research focused on the low wavenumber and uranyl stretching vibration regions.

Lattice dynamics and phase transitions in KNbO3 and K0.5Na0.5NbO3 ceramics.

Phonons in both ceramic samples KNbO(3) (KN) and K(0.5)Na(0.5)NbO(3) (KNN-50) were investigated from 10 to 900 K by means of Raman, infrared, and THz spectroscopy.