A5003153775- Ferroelectric and Piezoelectric Materials
- Microwave Dielectric Ceramics Synthesis
- Multiferroics and related materials
- Dielectric properties of ceramics
- Electronic and Structural Properties of Oxides
- Dielectric materials and actuators
- Advanced Sensor and Energy Harvesting Materials
- Magnetic and transport properties of perovskites and related materials
- Acoustic Wave Resonator Technologies
- Photonic and Optical Devices
- Photorefractive and Nonlinear Optics
- Advancements in Solid Oxide Fuel Cells
- Electrophoretic Deposition in Materials Science
- Nuclear materials and radiation effects
- Magnetic Properties and Synthesis of Ferrites
- Polymer Surface Interaction Studies
- Advanced ceramic materials synthesis
- Nanotechnology research and applications
- Innovative Microfluidic and Catalytic Techniques Innovation
- Electromagnetic wave absorption materials
- Pickering emulsions and particle stabilization
- Mechanical and Optical Resonators
- Polymer Nanocomposites and Properties
- Heat and Mass Transfer in Porous Media
- Magnesium Oxide Properties and Applications
Institute of Condensed Matter Chemistry and Technologies for Energy
2016-2024
National Research Council
2014-2023
University of Genoa
1999-2018
Institute for Macromolecular Studies
2018
Institute for Energetics and Interphases
2007-2016
Alexandru Ioan Cuza University
2014
University of Bucharest
2014
National Academies of Sciences, Engineering, and Medicine
2004-2011
Consorzio Roma Ricerche
2008
National Interuniversity Consortium of Materials Science and Technology
2008
A progressive reduction of tetragonal distortion, heat transition, Curie temperature, and relative dielectric constant has been observed on dense ${\mathrm{BaTiO}}_{3}$ ceramics with grain size decreasing from 1200 to $50\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. The correlations between size, extent ferroelectric properties strongly support the existence an intrinsic effect. From experimental trends critical for disappearance ferroelectricity evaluated be...
Theoretical models for small ferroelectric particles predict a progressive decrease of the Curie temperature, spontaneous lattice strain, and polarization until critical size corresponding to transition cubic phase disappearance ferroelectricity is reached. In contrast, behavior nanocrystalline $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ ceramics with grain $\ensuremath{\approx}30\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ dominated by extrinsic effects related boundaries which mask expected...
A structural study of Sm- and Gd-doped ceria was performed with the aim to clarify some unexplained features. (Ce1-xREx)O2-x/2 samples (RE ≡ Sm, Gd; x = 0, 0.1, ..., 1) were prepared by coprecipitation mixed oxalates subsequent thermal treatment at 1473, 1173, or 1073 K in air; they then analyzed room temperature both synchrotron X-ray diffraction μ-Raman spectroscopy. Two models adopted fit experimental data, namely, a fluoritic one, resembling CeO2 structure low RE content, hybrid one...
We investigate the second-harmonic generation (SHG) signal from single BaTiO3 nanoparticles of diameters varying 70 nm down to 22 with a far-field optical microscope coupled an infrared femtosecond laser. An atomic force is first used localize individual particles and accurately determine their sizes. Power polarization-dependent measurements on reveal diameter range between 30 20 nm, where deviations bulk nonlinear properties occur. For particles, tetragonal crystal structure not applicable...
The grain size influence on the dielectric relaxation and nonlinear properties of BaTiO 3 ceramics with in range (92÷936) nm densified by S park P lasma intering ( SPS ) from ultrafine powders were investigated. progressive reduction C urie temperature effective permittivity results a combination intrinsic effects low‐permittivity boundary layer. A model cylindrical cavities was employed order to calculate values GH z range. An interesting feature is presence thermally activated D ebye‐like...
Polymer-based nanocomposites containing inorganic ferroelectric inclusions, typically ABO3 perovskites, have emerged as innovative dielectric materials for energy storage and electric insulation, potentially coupling the high breakdown strength (BDS) easy processing of polymers with enhancement constant provided by phase. In this paper, experimental data three-dimensional finite element method (3D FEM) simulations were combined to shed some light on effect microstructures properties...
Barium titanate has been prepared by solid‐state reaction of nanocrystalline TiO 2 (70 nm) with BaCO 3 different particle size (650, 140, and 50 nm). The results give evidence a strong effect the in synthesis barium titanate. use already leads to formation single‐phase BaTiO after calcination for 8 h at 800°C. final powder consists primary particles ≈100 nm, narrow distribution d =270 no agglomerates larger than 800 nm. For coarser carbonate, 4 1000°C are required is much coarser....
The results of an atomistic simulation study on the incorporation ions first series transition metals (Cr 3+ , Cr 4+ Fe 2+ Co Ni and ), Y lanthanide (Er Gd Tb Pr La ) in BaTiO 3 lattice are presented discussed. prefer to substitute at titanium site with oxygen‐vacancy compensation. For iron cobalt, oxidation from divalent trivalent state during is favored. Nickel chromium preferentially incorporated valence 3+, respectively. Formation stable defect pairs different types defects predicted for...
Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro–para phase transition maximum permittivity of at 390 K and 1 kHz. local ferroelectric switching behaviour was investigated piezoresponse force microscopy. Typical piezoelectric hysteresis loops recorded different positions the sample. present results provide experimental evidence for polarization scale, indicating that critical disappearance in...
In the present work, diphasic ceramic composites with core-shell nanostructures formed by Ni0.50Zn0.50Fe2O4 core and BaTiO3 shell were investigated. Their properties compared those of prepared coprecipitation. The structure was confirmed microstructural powder analysis. Homogeneous microstructures a good phase mixing percolated dielectric magnetic one obtained from coprecipitated powders. Less homogeneous resulted in ceramics produced method, isolated small ferrite grains besides large...
The nonlinear dielectric properties of dense BaTiO3 ceramics with grain size 1 μm–90 nm were investigated. In the finest ceramics, permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [ε(E)] is obtained at high field, above 40 kV/cm. observed behavior was explained by considering nanostructured ceramic as composite formed ferroelectric grains, whose nonlinearity reducing, low-permittivity nonferroelectric boundaries, volume fraction increases when decreasing...
Many dielectric and semiconductor materials used for all-dielectric resonators or metasurfaces have low absorption in the near-infrared to visible range, but they are lossy near-ultraviolet (NUV) range due their energy band gap. Contrary this, ferroelectric lithium niobate (LiNbO3, LNO) has an gap larger than 4 eV and, consequently, very losses NUV down 310 nm. Here, we propose LNO nanocubes as a new alternative material nonlinear photonics range. We report that fabricated by solvothermal...
A systematic kinetic investigation on the chemical synthesis of BaTiO3 particles from aqueous solutions BaCl2 and TiCl4 at T < 100 °C pH 14 has been performed. Initially, a viscous suspension Ti-rich gel phase is obtained room temperature. Later, formation induced by heating above 70 gradually converted to crystalline perovskite. The isothermal kinetics evolution crystal size particle during course reaction are significantly influenced temperature, concentration, barium-to-titanium ratio...
Abstract The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity scale‐up problems encountered when using batch reactors. Supersaturation created by mixing the co‐reactants in micromixer inducing precipitation; suspension then segmented into identical micro‐volumes non‐miscible fluid sent through tube. These are more...
The formation of BaTiO 3 nanoparticles by a solid‐state reaction between nanocrystalline raw materials BaCO and TiO 2 was studied as function temperature (400°–800°C), time (1–24 h), titania particle size (15 30 nm). starts at 500°C high rate is already observed 600°C for the finest titania, with up to 90% conversion after h. Two main stages were 600°–700°C. first step dominated nucleation growth –BaCO contact points surface. Surface diffusion is, most likely, prevailing mass transport...
Cubic SrTiO3 particles are obtained by precipitation from an aqueous gel suspension. The suspension is prepared hydrolyzing a TiOCl2 solution with NaOH and adding SrCl2. addition of citric acid leads to spherical particles. particle size can be tailored in the range 80−1400 nm varying temperature concentration. A careful control synthesis conditions essential for producing narrow distribution. results HRTEM ED investigations provide strong evidence that oriented aggregation small (4−5 nm)...
Dielectric responses of ceramics from the lead-free isovalent BaZrO${}_{3}$-BaTiO${}_{3}$ (BZT) system were investigated Hz frequencies up to infrared in a broad temperature range, 10--700 K. Pure BaZrO${}_{3}$ is displacive weak-incipient ferroelectric with simple cubic perovskite structure down low temperatures, whose dielectric response fully determined by polar phonons, lowest-frequency one being Last type, unlike BaTiO${}_{3}$, where it Slater type. BaZr${}_{0.4}$Ti${}_{0.6}$O${}_{3}$...
The possible existence of a new kind ferroelectric order and the need to explore domain arrangement in nanostructures has stimulated an increasing activity on growth nanowires. In present study, single crystal BaTiO3 nanowires with tetragonal structure were obtained by original solid-state process using layered titania coated BaCO3 nanocrystals as reactive templates. Formation occurs at 700 °C topochemical reaction. Consequently, initial morphology is retained final product. Piezoresponse...
The mechanisms driving the mutual crystallographic alignment of nanocrystals in mesocrystals are various and not yet fully understood. As discussed this paper, formation can result from a topochemical reaction between single crystal particles or templates suspended liquid phase ionic/molecular species solution. In such case, initial particle morphology is retained final mesocrystal. If transformation topotactic, product will maintain no memory precursor morphology. magnitude lattice mismatch...