Ferroelectric materials for microwave tunable applications

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Ferroelectricity is a notable characteristic of certain materials, defined by a spontaneous electric polarization that can be reversed through the application of an external electric field. These ferroelectric materials also exhibit piezoelectric and pyroelectric properties, enabling the conversion of mechanical stress or temperature variations into electrical signals. Consequently, ferroelectric materials are highly valuable in a broad spectrum of applications, including sensors, actuators, and memory devi

Research into mesoscopic magnetic systems, which incorporate magnetic elements with dimensions ranging from a few nm up to a few 10s of micrometer, has been spurred on by the developments in their fabrication, characterisation, and control. Electron beam and optical lithography are key methods for their fabrication because they can be used to create tailor- made planar arrangements of elements or more complex layered structures. These can be further transformed into high quality three-dimensional mesoscale

Locally-resonant sonic metamaterials refer to synthetic acoustic matter composed of artificial acoustic “atoms”, generally passive, and of subwavelength sizes, that are capable of resonantly interacting with an external acoustic wave, and manipulate it in ways that are not directly available using natural bulk materials. Such artificial 3D materials, or their 2D analogs called metasurfaces, have led to extraordinary physical phenomena including negative refraction, subwavelength focusing, guiding or absorpt

It was noticed long time ago that the dielectric permittivity of BaTiO3 single crystals in the rhombohedral phase varies from observation to observation, but the microstructure mechanism behind this phenomenon remained unclear. We show that the variations in susceptibility can be related to the variable domain structure introduced by different pre-treatments at higher temperatures: Electrical depoling at room temperature leads to nano-sized domains and ultrahigh susceptibility in rhombohedral phase, whereas

This paper focuses on the fabrication and evaluation of vibration energy harvesting devices by utilizing an epitaxial Pb(Zr0.2Ti0.8)O-3 (PZT) thin film. The high quality of the c-axis oriented PZT layer results in a high piezoelectric coefficient and a low dielectric constant, which are key parameters for realizing high performance piezoelectric energy harvesters. Different cantilever structures, with and without a Si proof mass, are realized using micro-patterning techniques optimized for the epitaxial oxi

Béton brut and ineffable space: two concepts defined by Le Corbusier after World War II that speak about a stronger dialogue between materials and artistic vision of his work. Invented to designate his own particular use of exposed concrete, béton brut is analysed from different perspectives: its fabrication with a rigorous selection of its constituent materials; its textural imprint obtained by a refined assembly of formwork; and the treatment of its surface with special types of paint. In the synthesis of

Within the last years, an increasing number of studies have been carried out in the field of acoustic metamaterials. These artificial composite materials aim at achieving new macroscopic properties, like negative refraction, that are not readily present in nature. In analogy to electromagnetics, where such concepts are more mature, a novel concept of artificial acoustic transmission line has recently been reported, which presents such artificial behavior. In this article, the design of the proposed transmis

We report on the temperature dependence of ferroelectric metal-oxide-semiconductor (MOS) transistors and explain the observed improved characteristics based on the dielectric response of ferroelectric materials close to the Curie temperature. The hysteretic current-voltage static characteristics of a fully depleted silicon-on-insulator transistor, with 40 nm vinylidene fluoride trifluorethylene, and 10 nm SiO2 gate stack, are measured from 300 to 400 K. In contrast with conventional MOS field effect transis

The aim in this project was the optimization of LaFeO3-based perovskite materials for oxygen separation membranes (OSM). The work was carried out by the Laboratory for High Performance Ceramics, Empa in collaboration with the Laboratory for Industrial Energy Systems, LENI, EPFL and the Ceramics Laboratory, LC, EPFL. The ceramic material of interest is a mixed conductor for oxygen ions and electrons at high temperature (800°-900°C) and therefore can separate oxygen from nitrogen with 100% selectivity when

In ferroelectric materials, domain wall displacement plays a key role in the dielectric properties measured with respect to the driving field amplitude and frequency. The low to medium field dielectric response in many ferroic systems can be often described by classical Rayleigh model, which is rate-independent i.e., it depends only on the strength of ac signal. However experiments show that the nonlinear parameters are frequency dependent. Thus a more general approach, which can describe both purely nonlin

We investigate the dielectric permittivity of SiO2 on Si(100) substrates using a first-principles approach. It is shown that both the static and high-frequency dielectric constants of the oxide overlayer increase when the oxide thickness is reduced. This behavior of the overlayer is found to be well reproduced by a classical two-layer model in which the pure oxide and the suboxide layer are treated as distinct dielectrics. Implications for interfaces between silicon and high-k gate oxides are discussed. (C)

The importance of Fibre Reinforced Polymers (FRPs) as a material used for civil engineering purposes has grown in the last decade. Especially the introduction of pultrusion at an industrial level as a way to produce big batches of FRP made it possible to offer the advantages – like the high strength-to-weight ratio or the good corrosion resistance – at a reasonable cost. One issue when designing with pultruded FRPs are the connections. Up to now, connections between pultruded FRPs have been designed in the

The printing of lead zirconate titanate (PZT, Pb(Zr,Ti)O-3) piezoelectric thick films on silicon substrates is being studied for potential use as microactuators, microsensors, and micro.. transducers. A fundamental challenge in the fabrication of useful PZT thick-film devices on silicon is to sinter the PZT to high density at sufficiently low temperature to avoid mechanical or chemical degradation of the silicon substrate. The goal of the present study is to develop and implement suitable electrodes and PZT

Using a combined experimental and theoretical approach, we address C 1⁢𝑠 core-level shifts in amorphous carbon. Experimental results are obtained by x-ray photoelectron spectroscopy (XPS) and electron-energy-loss spectroscopy (EELS) on thin-film samples of different atomic density, obtained by a pulsed-laser deposition growth process. The XPS spectra are deconvoluted into two contributions, which are attributed to sp2- and sp3-hybridized atoms, respectively, separated by 0.9 eV, independent of atomic densit

Pb(Zr, Ti)O-3 (PZT) and Pb(Zr, Ti, Nb)O-3 (PNZT) thin films have been deposited on platinized silicon substrates by sputtering followed by a postannealing treatment. The Nb concentration in the films varied between 1 and 7 at. % with increments of 1 at. %. The effects of Nb modification on the piezoelectric response, and particularly on the longitudinal piezoelectric coefficient d(33), have been investigated. The introduction of Nb enhances the dielectric and piezoelectric properties of the PZT films. The b

A study of the complex permittivity in bismuth titanate was conducted to reveal the nature of an anomaly in the real part of the permittivity, which occurs below the Curie temperature. This anomaly is frequency dependent and is caused by a combination of two relaxation phenomena that appear in the imaginary part of the permittivity. One of the relaxations showed classic characteristics of an ion-jump process. Niobium doping suppressed this relaxation and eliminated the nonferroelectric anomaly in permittivi

Extending the useful life of materials through recycling has proven to be an efficient means of reducing natural resource use and limiting the production of waste. In the case of polymer-based materials, in general, and of packaging materials, in particular, material recovery is complicated by the presence of incompatible polymers, as well as a priori undesirable contaminants such as inorganic inclusions. This article investigated the recycling of multilayer packaging material systems, based on polypropylen

The non-linear dielectric properties of single crystals of PbMg1/3Nb2/3O3 relaxer ferroelectric were investigated experimentally by using measurements of the dielectric permittivity of this material as a function of the DC bias and the AC driving fields. The results were analyzed using four models of the dielectric response of relaxors currently discussed in the literature, It was shown that among them only one model was consistent with the experimental data. This provides strong evidence that the mechanism

The effective piezoelectric coefficient e(31) has been measured on sol-gel processed Pb(ZrxTi1-x)O-3 thin films with Zr concentrations ranging from 45 to 60%. The largest value was observed at 45% Zr, although dielectric constant and effective d(33) peak at 53% Zr. The findings suggest that the optimal composition for microactuators and sensors is less than or equal to 45% Zr, i.e., in the tetragonal part of the phase diagram.

Electron energy loss spectroscopy in a high-resolution transmission electron microscope has recently been used with success to characterize the electronic properties of closed cage nanometer-size graphitic particles. In the plasmon region, the experimental data reveal interesting size-dependent variations, which are not yet fully understood. The difficulties encountered in the interpretation of the spectra are principally due to the lack of a complete theoretical treatment of the anisotropic dielectric resp

Ferroelectric materials for microwave tunable applications

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Ferroelectric properties of III-V Semiconductors

Mesoscopic magnetic systems: From fundamental properties to devices

Active Acoustic Resonators and their Applications to Loss-Immune, Reconfigurable, or Dynamic Metamaterials

Unusual dielectric behavior and domain structure in rhombohedral phase of BaTiO3 single crystals

The realization and performance of vibration energy harvesting MEMS devices based on an epitaxial piezoelectric thin film

Le Corbusier: Béton Brut and Ineffable Space, 1940-1965

Design of Acoustic Metamaterials based on the Concept of Dual Transmission Line

Ferroelectric transistors with improved characteristics at high temperature

Optimization of mixed conducting perovskites for the application in dense ceramic oxygen separation membranes, used in partial oxidation of natural gas to synthesis gas

Analysis of the non linear domain wall response in ferroelectric thin films

Dielectric effect of a thin SiO2 interlayer at the interface between silicon and high-k oxides

Adhesively bonded lap joints of pultruded GFRP shapes

Processing and properties of screen-printed lead zirconate titanate piezoelectric thick films on electroded silicon

𝑠⁢𝑝²⁢/𝑠⁢𝑝³ hybridization ratio in amorphous carbon from C 1⁢𝑠 core-level shifts: X-ray photoelectron spectroscopy and first-principles calculation

Evaluation of niobium effects on the longitudinal piezoelectric coefficients of Pb(Zr, Ti)O-3 thin films

Niobium doping and dielectric anomalies in bismuth titanate

Effect of inclusions and blending on the mechanical performance of recycled multilayer PP/PET/SiOx Films

Mechanism of polarization response and dielectric non-linearity of PbMg1/3Nb2/3O3 relaxor ferroelectric

In-plane piezoelectric coefficient of PZT thin films as a function of composition

Plasmon excitations in graphitic carbon spheres