Paula Maria Vilarinho

Paula Maria Vilarinho
University of Aveiro | UA · Department of Materials and Ceramics Engineering

PhD In Materials Science

About

434
Publications
81,558
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
7,622
Citations
Introduction
My research is focused on electrical polarization phenomena in solids, aiming to understand mechanisms that control electrical polarization at macroscopic and nanoscale level, and applying such understanding to develop advanced nano and microelectronic devices. We have been using electrical and structural characterization to lead based and lead free oxide ferroelectrics, perovskite type insulators, multiferroic ferrite and manganite oxides, tellurium based oxides and piezoelectric polymers.
Additional affiliations
January 2002 - present
University of Aveiro
Position
  • Professor

Publications

Publications (434)
Article
The coordination of Mn in doped SrTiO <sub>3</sub> ceramics having nominal compositions SrTi <sub>0.98</sub> Mn <sub>0.02</sub> O <sub>3</sub> and Sr <sub>0.98</sub> Mn <sub>0.02</sub> TiO <sub>3</sub> was analyzed using x-ray absorption fine structure (XAFS) measurements. As expected, Mn <sup>4+</sup> substitution for Ti <sup>4+</sup> leads to Mn...
Article
We investigated the ceramics samples of multiferoic solid solution of relaxor ferroelectric Pb ( Fe <sub>2/3</sub> W <sub>1/3</sub>) O <sub>3</sub> with ferroelectric Pb Ti O <sub>3</sub> (abbreviated as PFW -x PT ; x=0 , 0.25, and 0.37) by means of acoustic emission (AE) method and simultaneously using the dielectric measurement below 700 K . A di...
Article
The characteristics of the diffuse phase transition of Pb(Fe <sub> 2/3 </sub> W <sub> 1/3 </sub> )O <sub> 3 </sub> relaxor ceramics doped with different amounts of Mn are investigated. The freezing temperature T<sub>f</sub>, obtained by fitting the ω,T<sub> max </sub> to the Vogel–Fulcher relationship, clearly changes with the Mn content. It increa...
Article
Full-text available
a b s t r a c t Carbon nanotubes (CNTs) have unique physical properties. This has been the driver for the current exploitation of their use in different advanced applications, such as in composite nanoscale devices. If a thermal treatment is required for the fabrication of the composite, the thermal decomposition behavior of the tubes is a key aspe...
Article
Full-text available
Piezoforce response microscopy was used for the first time to characterize the domain structure of 〈001〉-oriented potassium sodium niobate (KNN) single crystals revealing a long range ordered domain pattern of parallel 180° domains with zig-zag 90° domains. The grown KNN crystals have a high dielectric permittivity (29,100) at the tetragonal-to-cub...
Article
Full-text available
Alternative sintering technologies promise to overcome issues associated with conventional ceramic sintering such as high thermal budgets and CO 2 footprint. The sintering process becomes even more relevant for alkali-based piezoelectric ceramics such as K 0.5 Na 0.5 NbO 3 (KNN) typically fired above 1100 • C for several hours that induces secondar...
Article
An alternative sintering methodology, Spark Plasma Texturing (SPT), allowed us to prepare 98.0% dense lead free piezoelectric (K1-xNax)NbO3 (KNN) ceramics with a homogenous microstructure of small grains. In this work, Resonant Ultrasound Spectroscopy (RUS) was used to measure bulk, K, and shear, G, moduli of SPT KNN for comparison with conventiona...
Article
Full-text available
The voltage dependence of the dielectric permittivity ε’ and the low dielectric loss tanδ of incipient ferroelectrics have drawn vast attention to the use of these materials for the development of tun-ing elements in electronics and telecommunications. Here, we study the DC electric field depend-ence of low-temperature ε’ in ~320 nm thick sol-gel-d...
Article
Full-text available
The vital role of high-quality-factor (Q) high-frequency (f) dielectric resonators in the growing mi-crowave telecommunication, satellite broadcasting and intelligent transport systems has long mo-tivated the search for new, small size, and lightweight integrated components and packages, prepared by low cost and sustainable processes. One approach...
Article
In this article, a novel study of the design and characterization of barium strontium titanate (BST) thick films produced by electrophoretic deposition (EPD) on flexible platinum foils is reported. Intended for sub-6 GHz radio frequency (RF) applications, a study on film and electrode thickness is conducted. First, a comparison of tunability and qu...
Article
Full-text available
This paper presents a performance evaluation of single and dual-band software-defined radio (SDR) front-ends using commercially available barium strontium titanate (BST) thin film to control SDR receivers dynamic range and mitigate interference. Firstly, an SDR front-end solution using a BST-based single-band bandpass filter (BPF) is developed to m...
Article
Electric field and current applied to an unsintered ceramic body are known to promote low temperature and extremely fast densification, in a process referred to as FLASH sintering. Under the current urgency of the green transition of manufacturing processes, FLASH sintering is a very promising technology for materials industry. Suitable FLASH condi...
Article
Full-text available
Electrostatically coated abrasives have drawn vast attention in many industrial applications. Therefore, influence of humidity on the electrical properties of α-SiC and α-Al2O3 abrasive pow-ders with three μm-range particle sizes are here investigated using electrostatic charge and DC resistivity analysis. From the three particle size ranges used,...
Article
Full-text available
Strontium titanate-based materials with ferroelectric or relaxor-like properties have drawn vast attention as polar dielectrics for electronics and telecommunications. Here, we study the lattice dynamics in sol–gel-derived Sr1−1.5xBixTiO3 thin films with x = 0.0053 and 0.167, deposited on Al2O3 substrates, using a variable-temperature far-infrared...
Article
Full-text available
Alkali tantalates are encouraging functional materials with versatile properties that make them potential players in microelectronics, photocatalytic processes or medicine. Here, KTaO3 single crystals with 0.27% Li and 0.15% or 0.31% Mn contents determined by inductively coupled plas-ma spectroscopy analysis are studied at low temperatures using di...
Article
Full-text available
Alkaline niobate and tantalate perovskites have attracted attention as polar dielectrics for elec-tronics and telecommunications. Here, we studied the polar behaviour, lattice dynamics, and local structure in conventionally processed K0.985Mn0.015TaO3±δ ceramics using a combination of varia-ble-temperature dielectric and Raman spectroscopies, and X...
Presentation
Full-text available
SrTiO3-based compounds have been attracting considerable interest both for a wide range of applications and from a fundamental point of view. Fundamentally, perovskite-structured SrTiO3 undergoes a cubic (Pm3m) to tetragonal (I4/mcm) phase transition at ~108 K (Ta) associated with rotations of the O octahedra in antiphase around the [001] direction...
Article
Metals and their alloys make them critical materials in orthopaedic applications for bone support due to their biocompatibility and mechanical properties. Nevertheless, these materials do not stimulate bone regeneration. A way to overcome this problem, may involve the application of a coating over the alloys using biocompatible and biodegradable ma...
Article
In article 2100041, Arseniy Buryakov and co‐workers report on a new approach to significantly improve the performance (efficiency and spectrum width) of already well‐developed GaAs THz antennas. The cover shows three components of the proposed approach: the choice of the direction of the crystallographic cut of the GaAs substrate, a new design of t...
Article
Full-text available
Bone injuries represent a major social and financial impairment, commonly requiring surgical intervention due to a limited healing capacity of the tissue, particularly regarding critical-sized defects and non-union fractures. Regenerative medicine with the application of bone implants has been developing in the past decades towards the manufacturin...
Conference Paper
In this paper, the samples preparation, experimental details, and characterization of the Electrophoretic Deposition (EPD) of a thick film Barium Strontium Titanate (BST) capacitor intended for radio-frequency applications are reported. With a bias voltage from 0 V to 20 V, the Ba 0.7 Sr 0.3 TiO 3 capacitor fabricated demonstrates 49% of tunability...
Article
Stimuli responsive materials are found in a broad range of applications, from energy harvesters to biomolecular sensors. Here, we report the production of poly (L-lactic acid) (PLLA) thin films that exhibit a mechanical stress responsive behaviour. By simply applying a mechanical stress through an AFM tip, a local electrical polarization was genera...
Article
Full-text available
An alternative approach is proposed to improve the conventional (based on the low‐temperature grown GaAs and Si‐doped GaAs superlattice) photoconductive antenna (PCA) performance by modification of the planar electrodes design and crystallographic orientations of the GaAs substrate ((100) and (111)‐A). The electrode scheme design includes a combina...
Article
This work is devoted to disclosing the effect of epitaxial strain on crystallographic, transport, and nonlinear optical properties of a bilayer structure consisting of one ferroelectric (FE) (BaTiO 3 with a thickness of 4 nm) and one ferromagnetic (La 0.7 Ca 0.3 MnO 3 with the thickness of 12 nm) layers. Both tensile (of about ∼6% caused by the MgO...
Article
Full-text available
The considerable decrease in temperature and time makes FLASH sintering a more sustainable alternative for materials processing. FLASH also becomes relevant if volatile elements are part of the material to be processed, as in alkali-based piezoelectrics like the promising lead-free K0.5Na0.5NbO3 (KNN). Due to the volatile nature of K and Na, KNN is...
Article
There is currently a demand for flexible biomedical sensors. Characteristics as soft, thin, elastic, flexible and comfortable to the contact with skin should be matched with performance and ultimately made of sustainable, and biocompatible materials. In this work, chitosan as a flexible biodegradable polymeric matrix was combined with ferroelectric...
Article
The Front Cover shows a flexible functional biocomposite film composed of chitosan biopolymer and BaTiO3 particles, which was prepared by environmentally benign methodologies. This film is flexible, and its elasticity can be tailored by the addition of BaTiO3 particles. The dielectric permittivity increases with the barium titanate content. The evi...
Article
Cubic bismuth zinc niobate (c-BZN) thick films were fabricated on flexible platinum foils by electrophoretic deposition technique. The X-ray diffraction studies reveal that the films are under tensile stress. The permittivity of the c-BZN thick film sintered at 850 and 950°C, measured at an applied frequency of 1 MHz were 114 and 125, respectively....
Article
In this work, we revisit the phase transition sequence and the effect of the sintering process on the structural, dielectric and polar properties of K0.5Na0.5NbO3 ceramics prepared by conventional sintering, spark plasma sintering and spark plasma texturing. Herein, comparative experimental study of the lattice dynamics, polar and dielectric proper...
Presentation
Full-text available
Invited Talk------------------------------------------------------------------------------------------------------------------Development of giant-permittivity and high-tunability dielectric materials has attracted great interest because of growing demand for smaller and faster energy-storage and electronic devices [1-3]. Materials such as CaCu3Ti4...
Article
The Front Cover shows a schematic on the relevance of the thermal cycle for the FLASH sintering of lead‐free piezoelectric K0.5Na0.5NbO3 (KNN). The use of an Isothermal Condition (I.C.) prior to the FLASH event allows neck formation and particle surface smoothening. Therefore, a more uniform current distribution upon FLASH is achieved, as shown by...
Article
Full-text available
The purpose of this selective review is primarily to demonstrate the large versatility of the insulating quantum paraelectric perovskite SrTiO3 explained in "Introduction" part, and "Routes of SrTiO3 toward ferroelectricity and other collective states" part. Apart from ferroelectricity under various boundary conditions, it exhibits regular electron...
Article
Full-text available
Potassium sodium niobate, K0.5Na0.5NbO3 (KNN) is a lead‐free piezoelectric with the potential to replace lead zirconate titanate (PZT) in electromechanical applications. Due to its cuboid particle morphology and volatile elements, monophasic and dense ceramics are difficult to obtain via conventional sintering. In this work, isothermal FLASH sinter...
Article
A indústria cerâmica tradicional e técnica é um dos principais setores com avultadas emissões de gases de carbono, dada a necessidade de etapas de cozedura a temperaturas elevadas, geralmente superiores a 1000 ºC. Diretrizes recentes da união europeia, materializadas no European Green Deal, indicam que a europa deverá ser um continente neutro em em...
Article
Controlling the sintering and microstructure of lead-free potassium sodium niobate ((K1-xNax)NbO3, KNN) ceramics is of primary importance to optimize its piezoelectric / ferroelectric properties. However, sintering dense and monophasic KNN remains a challenge. Here, we prepare KNN ceramics using spark plasma texturing (SPT), a modified spark plasma...
Article
The last few years have seen an upsurge in attention towards the investigation and application aspect of the electro-optic properties of ferroelectric materials. The current work reports the effect of substrates on the optical characteristics of the lead zirconate titanate (PZT) thin films fabricated via the novel sol–gel route. The PZT thin films...
Article
ZnO/ZnO2 composites grown by hydrothermal synthesis at low temperature (180 °C) and thermally annealed at 300 °C were fully analysed by morphological, structural and optical techniques. X-ray diffraction patterns (XRD) and Raman spectroscopy clearly evidences the presence of both crystalline phases in the ZnO/ZnO2 sample. The differential scanning...
Article
FLASH sintering is a field-assisted technique that allows the densification of ceramics in a few seconds at temperatures significantly lower than those of conventional cycles. There is still discussion among the scientific community about the mechanism behind this sintering process, that has been typically attributed to Joule heating, defect creati...
Article
Full-text available
If piezoelectric micro-devices based on K0.5Na0.5NbO3 (KNN) thin films are to achieve commercialization, it is critical to optimize the films’ performance using low-cost scalable processing conditions. Here, sol–gel derived KNN thin films are deposited using 0.2 and 0.4 M precursor solutions with 5% solely potassium excess and 20% alkali (both pota...
Article
Lead-free potassium sodium niobate (K0.5Na0.5NbO3, KNN) piezoelectric ceramics have been densified at temperatures lower than 300 ºC using atmosphere-water assisted FLASH sintering. Transmission electron microscopy (TEM) studies revealed amorphous phase at grain boundaries that resulted from surface melting of the cuboid particles in the presence o...
Chapter
Full-text available
Among the lead-free perovskite-structure materials, strontium titanate (SrTiO3 - ST) and potassium tantalate (KTaO3 - KT), pure or modified, are of particular importance. They are both quantum paraelectrics with high dielectric permittivity and low losses that can find application in tunable microwave devices due to a dependence of the permittivity...
Chapter
Currently much worldwide research is focused on clean and sustainable energy sources that can respond to the rising energy demands of the world. Thermoelectric (TE) harvesting of unused heat in automotive exhaustion, industrial processes and home heating will increase the efficiency of energy use, while simultaneously reducing the CO2 emissions. Al...
Chapter
Among the lead-free titanate-based materials, strontium titanate (SrTiO3), pure or modified, is of particular importance. SrTiO3 is an incipient ferroelectric with high dielectric permittivity and low losses, which finds application in tunable microwave devices due to a dependence of the permittivity on the electric field, or in grain-boundary barr...
Chapter
Strontium titanate-based materials with ferroelectric or relaxor-like properties have drawn vast attention for research and wide range of applications in different areas. This chapter summarises firstly the electrical behaviour of Bi-doped strontium titanate ceramics, where three relaxation modes, related to individual hopping of off-centre Bi ions...
Book
Strontium titanate (STO) is a classical high-permittivity perovskite material known since the forties of the last century. Although incipient ferroelectric behaviour of SrTiO3 was thoroughly studied during several decades many new physical phenomena in STO and its solid solutions were predicted theoretically and observed experimentally in last seve...
Article
Full-text available
Nanopatterned porous thin films of bismuth ferrite (BiFeO3) with porosity perpendicular to the plane are prepared by an evaporation-induced self-assembly methodology using nitrate metal salts and a commercial block copolymer as a structure-directing agent. The sol–gel based method is successfully used to achieve crystalline nanopatterned porous BiF...
Article
Untargeted Nuclear Magnetic Resonance (NMR) metabolomics was employed, for the first time to our knowledge, to characterize the metabolome of Human Osteoblast (HOb) cells and extracts in the presence of non‐poled or negatively poled poly‐L‐lactic acid (PLLA). The metabolic response of these cells to this polymer, extensively used in bone regenerati...
Poster
Full-text available
First prize of the poster contest -------------------------------------------------------------------------------------- FLASH is an electric field-assisted sintering technique recently proposed to densify materials in a more sustainable, energy reductive and cost-effective way than conventional sintering (CS). FLASH sintering promotes the densifi...
Article
The Fe-doped PZT, Pb (Zr, Ti) 1-x Fe x O 3 , ceramics have gathered plenty of attention because of the interplay of ferroelectric and ferromagnetic properties. In the present study, we report the properties of Pb(Zr 0.52 Ti 0.48 ) 1-x Fe x O 3 prepared by conventional solid-state reaction route with varying Fe ³⁺ doping concentrations, x = 0, 0.05,...
Article
Full-text available
In the context of bone regeneration, it is important to have platforms that with appropriate stimuli can support the attachment and direct the growth, proliferation and differentiation of the cells. In the orthopedic field, metals and alloys are still the dominant materials used as implants, though their bioinert character leads to failure or to th...
Chapter
Low cost scalable processing and substrates are critical for optimized polar dielectric performance of functional oxide thin films if they are to achieve commercialization. Here, we present a comprehensive investigation of the role low-cost MgO, Al2O3, SrTiO3 and Si substrates on the structural and electrical properties of sol-gel derived SrTiO3 (S...
Article
The effect of nonstoichiometry (Sr/Ti ratio from 0.995 to 1.02) on the bulk and grain boundary contributions to the electrical response of strontium titanate (STO) ceramics is investigated. Nonstoichiometric STO exhibits lower electrical resistivity than its stoichiometric counterpart. This decrease is systematic for both Ti and Sr-excess and with...
Article
Recently we have demonstrated that out-of-plane dielectric properties of polycrystalline SrTiO3 (ST) films depend on the strain/stress induced by the substrates due to thermal expansion misfit. Here, we present a complementary infrared (IR) spectroscopy investigation of the role of Al2O3 and MgO substrates on the lattice dynamics and in-plane diele...
Article
Obtaining high quality BiFeO3 thin-films by low-cost scalable chemical solution deposition (CSD) is still challenging and currently relevant. Here we provide a comprehensive set of experimental evidences on the role of metallic (Pt) and oxide (IrO2 and LaNiO3) electrode interfaces on the texture development and functional properties improvement of...
Article
Full-text available
Different concentrations of N (0, 1, 3 and 5 wt.%) added ZnO thin films were primed using spin coater. X-ray diffraction (XRD) patterns confirm the preferred growth orientation of all films along (0 0 2) plane, however, ITO has dominant features owing to low thickness of the films. XRD along with vibrational spectroscopy confirms the single hexagon...
Article
Full-text available
If piezoelectric thin films sensors based on K0.5Na0.5NbO3 (KNN) are to achieve commercialization, it is critical to optimize the film performance using low-cost scalable processing and substrates. Here, sol–gel derived KNN thin films are deposited using a solution with 5% of potassium excess on Pt/TiO2/SiO2/Si and Pt/SrTiO3 substrates, and rapid t...
Article
Sol-gel spin coating is applied to fabricate the pure and different concentrations of aluminium (Al) doped ZnO films on high-quality silicon substrates. All films are showing high crystallinity in X-ray diffraction study and lattice constants were obtained using POWDERX software. The value of crystallite size was found in range of 20 - 40 nm. EDX/S...
Article
Full-text available
Direct ink writing has become a widespread additive manufacturing technique for material engineering, but its application in lead‐free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) piezoelectric ceramics from aqueous systems has not been reported so far to our knowledge. The main obstacle is the high extent of hydrolysis reactions undergone by the starting powde...
Article
The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr0.52Ti0.48)O3] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20 at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were empl...
Article
An alternative low cost flexible processing is utilized to fabricate tunable dielectric thick-films with low loss. By using a combination of electrophoretic deposition with chemical solution deposition, 9 μm-thick BaNd2Ti5O14-Ba0.5Sr0.5TiO3 (BNT-BST) composite films are fabricated with a room-temperature relative permittivity of 287 and a loss tang...
Presentation
Full-text available
Maker´s Lab the new Laboratory of the Electroceramics Group: Why?, the mission, the vision, the lab of Additive Manufacturing
Article
Titanium-rich (Sr/Ti = 0.995) strontium titanate (ST) ceramics, air-sintered in a temperature range of 1400–1625 °C, were reported to possess anomalies in the grain growth and analogous anomalies in the grain boundary (GB) conductivity activation energy. However, these two interface-related phenomena, occurring at GBs, could not be associated with...
Article
Full-text available
This article deals with poly crystalline Zinc Oxide (ZnO) films fabricated on ultrasonicated clean glass substrate by solgel spin coating. X-Ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-Visible spectroscopy (UV-Vis.), are utilized to describe the fabricated ZnO films. The X-Ray diffraction (XRD) pattern infe...
Article
Optimizing performance using low cost scalable processing and substrates is critical if functional oxide thin films are to achieve commercialisation. Here, we present a comprehensive investigation of the role low cost Al2O3, SrTiO3, MgO substrates on the structure, microstructure and electrical properties of SrTiO3 (ST) thin films, deposited by sol...
Article
Full-text available
Nanocrystalline ZnO thin films were deposited on glass substrate via sol–gel dip-coating technique then annealed at 300°C, 400°C, and 500°C for 1 h. Their optical, structural, and morphological properties were studied using ultraviolet–visible (UV–Vis) spectrophotometry, x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). XRD...
Article
Tissue engineering is evolving towards the production of smart platforms exhibiting stimulatory cues to guide tissue regeneration. This work explores the benefits of electrical polarization to produce more efficient neural tissue engineering platforms. Poly (l-lactic) acid (PLLA)-based scaffolds were prepared as solvent cast films and electrospun a...