Relaxor ferroelectrics were discovered almost 50 years ago among the complex oxides with perovskite structure. In recent years this field of research has experienced a revival of interest. In this paper we review the progress achieved. We consider the crystal structure including quenched compositional disorder and polar nanoregions (PNR), the phase transitions including compositional order-disorder transition, transition to nonergodic (probably spherical cluster glass) state and to ferroelectric phase. We discuss the lattice dynamics and the peculiar (especially dielectric) relaxation in relaxors. Modern theoretical models for the mechanisms of PNR formation and freezing into nonergodic glassy state are also presented.

Recent progress in relaxor ferroelectrics with perovskite structure

Transparent conductors as solar energy materials: A panoramic review

Surface Chemistry of Ruthenium Dioxide in Heterogeneous Catalysis and Electrocatalysis: From Fundamental to Applied Research

Correlated electron materials can undergo a variety of phase transitions, including superconductivity, the metal-insulator transition and colossal magnetoresistance. Moreover, multiple physical phases or domains with dimensions of nanometres to micrometres can coexist in these materials at temperatures where a pure phase is expected. Making use of the properties of correlated electron materials in device applications will require the ability to control domain structures and phase transitions in these materials. Lattice strain has been shown to cause the coexistence of metallic and insulating phases in the Mott insulator VO(2). Here, we show that we can nucleate and manipulate ordered arrays of metallic and insulating domains along single-crystal beams of VO(2) by continuously tuning the strain over a wide range of values. The Mott transition between a low-temperature insulating phase and a high-temperature metallic phase usually occurs at 341 K in VO(2), but the active control of strain allows us to reduce this transition temperature to room temperature. In addition to device applications, the ability to control the phase structure of VO(2) with strain could lead to a deeper understanding of the correlated electron materials in general.

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Strain engineering and one-dimensional organization of metal–insulator domains in single-crystal vanadium dioxide beams

The methods used to deposit a catalyst on structured surfaces are reviewed. Physical methods such as PVD and chemical methods (sol–gel, CVD, direct synthesis, etc.) are described. The coating of catalysts based on oxide, zeolite or carbon support is detailed on various surfaces such as silicon or steel microstructured reactors, cordierite monoliths or foams, fibres, tubes, etc.

Review on methods to deposit catalysts on structured surfaces

The perovskite structure of the relaxor PbMg1/3Nb2/3O3 (PMN) is studied using X-ray and neutron powder diffraction data. The static diffuse scattering (SDS) observed in the diffraction patterns at low temperatures is interpreted using a two-phase Rietveld analysis. The structural model is based on a long-range structure with an average cubic symmetry, and a short-range order due to atomic shifts involved by the formation of polar regions. The two-phase model provides a good improvement in reliability factors. The correlation length and the coexistence of different phases at low temperatures are discussed.

https://iopscience.iop.org/article/10.1088/0953-8984/3/42/011/pdf

A structural model for the relaxor PbMg1/3Nb2/3O3 at 5 K

X-ray and neutron diffraction studies of the diffuse phase transition in PbMg13Nb23O3 ceramics

http://jcvalmal.univ-tln.fr/articles/TFVO2.pdf

Optimized infrared switching properties in thermochromic vanadium dioxide thin films: role of deposition process and microstructure

The thermochromic vanadium dioxide. I. Role of stresses and substitution on switching properties

The carbonatation of La2O3 oxide and the decarbonatation of lanthanum carbonate phase La2O2CO3 are investigated using thermal and thermogravimetry analyses under CO2 gas flow. The initial phase La2O3 is first elaborated from pyrolysis of a LaOHCO3 precursor. Then, thermal and thermogravimetry analyses are carried out under CO2 flow, as temperature increases then decreases. The carbonatation kinetics of La2O3 is determined at three fixed temperatures. Electrical impedance spectroscopy is performed to determine the electrical responses associated with ionic mobilities and phase changes, in the temperature range 25 to 900∘C. The electrical conduction during heating under CO2 gas flow should be linked to two regimes of ionic conduction of the carbonate ions. From these electrical measurements, the ionic mobility of carbonate ions CO32− is found to be close to 0.003 ·10−4 cm2 s−1 V−1 at 750∘C for the monoclinic La2O2CO3 phase.

/pdf/carbonatation-and-decarbonatation-kinetics-in-the-la2o3-3svixib4bz.pdf

Jean-Raymond Gavarri

Papers

A structural model for the relaxor PbMg1/3Nb2/3O3 at 5 K

X-ray and neutron diffraction studies of the diffuse phase transition in PbMg13Nb23O3 ceramics

Optimized infrared switching properties in thermochromic vanadium dioxide thin films: role of deposition process and microstructure

The thermochromic vanadium dioxide. I. Role of stresses and substitution on switching properties

Carbonatation and Decarbonatation Kinetics in the La2O3-La2O2CO3 System under CO2 Gas Flows