Mojca Otoničar

Jožef Stefan Institute | IJS · Electronic Ceramics Department

Recently, piezoelectric-based catalysis has been demonstrated to be an efficient means and promising alternative to sunlight-driven photocatalysis, where mechanical vibrations trigger redox reactions. Here, we show that 60 nm average size BiFeO3 nanoparticles are very effective for piezo-degrading Rhodamine B (RhB) model dye with record degradation...

The archetypical antiferroelectric, PbZrO3, is currently attracting a lot of interest, but no consensus can be clearly established on the nature of its ground state as well as on the influence of external stimuli over its physical properties. Here, the antiferroelectric state of 45-nm-thick epitaxial thin films of PbZrO3 is established by observing...

A novel and effective antibacterial agent based on a combination of copper nanoparticles (CuNPs) and polypyrrole (PPy) is presented. By using a straightforward in situ polymerization method in water, a copper/polypyrrole (Cu/PPy) nanocomposite with spherical CuNPs, around 25 nm in diameter, uniformly dispersed throughout a granular PPy matrix, was...

Multiferroic materials have attracted significant research attention due to their technological potential for applications as multifunctional devices. The scarcity of single-phase multiferroics and their low inherent coupling between multiferroic order parameters above room temperature pose a challenge to their further applications. We propose a 3...

Magnetoelectric multiferroics are provoking much research activity for their potential applications in novel multifunctional devices. Compared with single-phase multiferroics, magnetoelectric composites have competitive advantages. The magnetoelectric coupling of composites is heavily influenced by composition and grain size. We prepared BFO/PZT co...

The main limitations of current methods for synthesizing perovskite oxide (ABO3) nanoparticles (NPs), e.g., the high reagent costs and sophisticated equipment, the long time and high‐temperature processing, or multiple post‐processing and thermal treatment steps, hamper their full study and potential application. Here, we use a facile low temperatu...

The main limitations of current methods for synthesizing perovskite oxide (ABO3) nanoparticles (NPs), e.g., the high reagent costs and sophisticated equipment, the long time and high‐temperature processing, or multiple post‐processing and thermal treatment steps, hamper their full study and potential application. Here, we use a facile low temperatu...

BiFeO3 is the model multiferroic material widely considered as nanoparticles for its potential photocatalytic activity. In this work, we study the influence of annealing temperature on the structural, morphological and optical properties of BiFeO3 nanoparticles prepared by a facile chemical route and, the resulting photodegradation of Eosin B dye....

Gold polypyrrole (AuPPy) and copper polypyrrole (CuPPy) nanocomposites were prepared by a simple one-step in situ oxidative polymerization of pyrrole monomer by Au³⁺ and Cu²⁺ ions. Owing to their characteristic physicochemical properties confirmed by optical and structural characterization methods, the behavior of these materials as electrocatalyst...

The dynamic contribution of domain walls to application‐relevant dielectric and piezoelectric properties of ferroelectrics and relaxor‐based oxide ceramics has been in the focus since the earliest studies on these complex multifunctional materials. Despite the vital importance of domain walls in the material design for targeted applications, the un...

Nanocomposites of gold nanoparticles (AuNPs) and conducting polymers, polypyrrole (PPy) and polyaniline (PANI), were prepared by simple oxidative polymerization of the corresponding monomer (pyrrole and aniline, respectively) by tetrachloroauric acid. Au nanospheres and nanorods were formed in the case of [email protected] and [email protected], re...

In materials science, intentional doping has been widely used to improve the properties of a variety of materials. However, such an approach is not yet exploited in the fast-growing field of electrocaloric materials, which represent a serious alternative for next-generation cooling systems. Here we demonstrate with Ba0.9Sr0.1Hf0.1Ti0.9O3, an ecofri...

The dielectric and piezoelectric response of the Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) polycrystalline ceramics after different poling procedures is examined and explained with respect to the phase composition and the domain structure. In the monoclinic (M) compositions a twice lower AC poling field is needed for a similar piezoelectric coefficient (d3...

Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN-10PT) ceramic prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The d...

Despite the challenges of practical implementation, electrocaloric (EC) cooling remains a promising technology because of its good scalability and high efficiency. Here, we investigate the feasibility of an EC cooling device that couples the EC and electromechanical (EM) responses of a highly functionally, efficient, lead magnesium niobate ceramic...

Soy isoflavone genistein (Gen) exerts beneficial effects against prostate cancer cells in vitro and in vivo. However, its use as a chemoprevention/therapeutic agent is largely limited due to its low bioavailability. In this study we synthesized two variants of a new delivery system, genistein–gold nanoparticles conjugates [email protected] and [ema...

The polarization and strain response of ferroelectric materials at fields below the macroscopic coercive field is of a paramount importance for the operation of many electronic devices. The response of real ferroelectric and related materials is in general complex and difficult to interpret. The reason for this is that many processes in a ferroelec...

The polarization and strain response of ferroelectric materials at electric fields below the macroscopic coercive field is of paramount importance for the operation of many electronic devices. The response of real ferroelectric and related materials is, in general, complex and difficult to interpret. The reason for this is that many processes in a...

The combination of significant polarization and large light absorption is a challenge in ferroelectric materials. Here we report the optical absorption of BaTiO3codoped with trivalent and pentavalent transition metal ions replacing the Ti⁴⁺cation,i.e., BaTi1−x(X1/2Y1/2)xO3(X = Sc, Mn, Fe, Co; Y = Nb, Ta; withx= 0.075). We investigated the optical a...

The scarcity of single-phase magnetoelectric multiferroics has motivated active research towards the design of composites where polarization and magnetization are coupled through elastic strain at their interfaces. Up to now, most of bulk multiferroic composites are made of immiscible constituents that thus suffer from weak interface connectivity b...

Supplementary information to adfm202006823

Lead-based relaxor ferroelectrics are characterized by outstanding piezoelectric and dielectric properties, making them useful in a wide range of applications. Despite the numerous models proposed to describe the relation between their nanoscale polar structure and the large properties, the multiple contributions to these properties have not yet be...

Lead-free piezoelectric ceramics have emerged as a topic of intense scientific interest in the early 2000 in response to enhanced environmental awareness supported by impending legislation. Candidates to replace highly efficient lead-based piezoelectric ceramics include alkali niobate, sodium bismuth titanate and barium titanate-based formulations....

We report on a heterogeneity study, down to the atomic scale, on a representative multiple-element-modified ceramic based on potassium sodium niobate (KNN): 0.95(Na 0.49 K 0.49 Li 0.02)(Nb 0.8 Ta 0.2)O 3-0.05CaZrO 3 with 2 wt % MnO 2. We show that different routes for incorporating the MnO 2 (either before or after the calcination step) affect the...

A first-order ferroelectric phase transition is driven supercritically in multilayer capacitors of PbSc0.5Ta0.5O3, enabling an electrocaloric response of 5.5 K near room temperature.

There is a need for developing new and perspective materials for oxygen reduction reaction (ORR) as one of the most essential reactions in the life processes, energy storage, and conversion, in order to exchange the most often used materials based on platinum supported/unsupported substrates, especially carbon supports. Herein, we present low-cost...

we undertake a novel sintering approach called the cold sintering method to design a perovskite–perovskite particulate composite from two ferroic phases.

Electrocaloric fatigue, i.e., the degradation of the electrocaloric temperature change of an active material under continuous electric-field cycling, has not been addressed in detail so far, despite the elevated electric fields expected for EC cooling devices. Here, we investigate the electrocaloric fatigue mechanism of a prototype relaxor material...

Phase pure NaNb1−xTaxO3 ceramics have been successfully prepared by spark plasma sintering (SPS) process at 950–1150 °C. The structural evolution, dielectric and energy storage properties as a function of Ta-doping level were studied by X-ray diffraction (XRD) Rietveld refinement, X-ray photoelectron spectroscopy (XPS), high resolution transmission...

A systematic investigation of the seeding effects on the mechanochemical synthesis of lead magnesium niobate – lead titanate 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN–10PT), one of the most studied relaxor-ferroelectric material for electrocaloric applications, is reported. The perovskite crystallisation process was followed by X-ray diffraction using the...

Changes to the crystal structure of 0.70Pb(Mg1/3Nb2/3)O3−0.30PbTiO3 (PMN-0.30PT) piezoceramic under application of electric fields at the long-range and local scale are revealed by in situ high-energy x-ray diffraction (XRD) and pair-distribution function (PDF) analyses, respectively. The crystal structure of unpoled samples is identified as monocl...

A facile and fast aqueous phase-based strategy to synthesize silver-polyaniline-polyvinylpyrrolidone (Ag-PANI-PVP) nanocomposites, via chemical oxidative polymerization method is presented. In the presence of polyvinylpyrrolidone (PVP), which has an accelerating effect on the oxidation of aniline with silver nitrate, Ag nanoparticles (AgNPs) were i...

The vast majority of studies on field-induced changes in (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–xPT) materials at the morphotropic phase boundary (MPB) have been performed on single crystals, while the more complex responses in polycrystalline materials have not yet been resolved. By using combined microscopy and diffraction techniques, this study aims...

A model organic pigment (diketopyrrolopyrrole) is encapsulated by a silica coating in order to improve its photochemical stability. Unlike in previous works where single-layer silica coatings were used for similar purposes, we here propose creation of a multi-layer silica shell synthesized via in-situ sol-gel method, which should significantly impr...

Lead-free perovskites based on Na 0.5 Bi 0.5 TiO 3 (NBT) are being considered as viable alternatives to lead-containing piezoelectric materials. The piezoelectric response of morphotropic compositions of these bismuth-based piezoelectrics during the application of external stimuli are governed by an intrinsic local disorder, ferroelectric and antif...

Electromechanical properties and crystal and domain structures of piezoelectric ceramics from the Pb1-xLax(Zr0.65Ti0.35)1-x/4O3 (x/65/35 PLZT) solid solution system were systematically analysed by electrical measurements, X-ray diffraction and scanning electron microscopy. The compositionally-driven phase transition from a rhombohedral ferroelectri...

We report a simple and green procedure for the preparation of magnetic iron oxide nanocrystals via solvothermal synthesis. The nanocrystal synthesis was carried out under mild conditions in the water-ethanol-oleic acid solvent system with the use of the oleate anion as a surface modifier of nanocrystals and glucose as a reducing agent. Specific con...

In-situ-heating transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses were performed on the (Na1�xKx)0.5Bi0.5TiO3 perovskite solid solution at the morphotropic phase boundary (MPB) in order to evaluate the structural contribution to the enhanced electromechanical properties of piezoelectrics. Prior to heating in the TEM, the M...

A bio-inspired approach to photocatalysis with a selection of biologically acceptable building blocks that can be activated by non-toxic visible light is a direction of research for the design of advanced, biomaterials that are able to induce self-cleaning. Here we show that a combination of hydroxyapatite (HAp) with platinum (Pt0 and Ptn+) is suit...

The solid-state reaction synthesis of K0.5Bi 0.5TiO3 and (1-x)Na0.5Bi0.5TiO 3-xK0.5Bi0.5TiO3 solid solutions was investigated using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy and Knudsen effusion combined with mass spectrometry. The results revealed the volatilization of the potassium and bismut...

The local crystal and domain structures of K0.5Bi0.5TiO3 ceramics were investigated by transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). The individual grains showed a lamellar domain structure, and on the basis of spot splitting along the characteristic crystallographic directions, 90°a–a- and 90°a–c-type domain...

We have investigated the Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 (NBT–KBT) system, with its complex perovskite structure, as a promising material for piezoelectric applications. The NBT–KBT samples were synthesized using a solid-state reaction method and characterized with XRD and SEM. Room-temperature XRD showed a gradual change in the crystal structure from...

This article presents the findings of a study that comprised laboratory investigations of hydraulic permeability of clays, comparison of measured coefficients of hydraulic permeabilitywith the predicted coefficients obtained according to procedures proposed by different researchers, and the analysis of the influence of individual physical propertie...