Symposium CI
Progress in Electroceramics Research
ABSTRACTS
CI-1:IL01 Two Approaches to Develop Ultra-low Permittivity Ceramics for High Frequency Applications
M. Nelo, H. Jantunen, Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, Oulu, Finland
In the future, the passive devices for wireless telecommunication need not only low losses but also low permittivity due to the higher frequencies. This presentation shows two ways to fabricate dielectrics with relative permittivity close one at GHz frequencies. In the first approach, the method is inspired by the paper making process using Li2MoO4, hollow micron-sized glass spheres and quartz fibers. The surfaces of the sandwich like structures were then covered with nano cellulose fibers to improve the smoothness. These samples were heat treated only at 120oC. The second approach is also based on Li2MoO4 and hollow micron-sized glass spheres, but the samples are fabricated using tape casting and sintering procedure. The resulting permittivity values in both cases were close to one with losses in the scale of 10-3-10-4 at 5-10 GHz. Additionally, chemical compatibility with silver ink was approved.
CI-1:IL02 Glasses and Glass Ceramics: Properties and Applications in Microwave Electronics
M. LETZ, SCHOTT AG, Mainz, Germany
The progress of GHz electronics in application areas like 5G mobile communication, automotive radar or gesture recognition requires increasingly more sophisticated designs of high frequency filter and antenna structures. Glasses and glass-ceramics are a class of materials which show very high homogeneity. Optical glasses are usually produced in a homogeneity which allows to control wave-front aberration of electromagnetic radiation with a wavelength of a few hundred nanometer, called visible light. Therefore glasses and glass ceramics are also well suited as dielectric materials in antenna structures in the GHz range where highly precise designs are needed. Further on the low thermal coefficients of glasses and glass ceramics allow to operate electronics using such materials in a wide temperature range. The dielectric constant of glasses covers a range from 3.8 < eps' < 21, using glass ceramics also larger dielectric constant values can be realized. Depending on the frequency of application where either antenna miniaturization or highly precise broad band antennas are needed, one can choose the right glass, which best fits with its dielectric properties. In the present work we give a number of examples were glasses and glass ceramics are used in antenna and/or filter applications in high frequency electronics.
CI-1:IL04 Anomalous Domain Wall Motion in Cu-Cl Boracite: Implication for Negative Capacitance
C. Cochard1, 2, J.G.M. Guy1, R.W. Whatmore3, M. Conroy4, K. Moore4, A. Harvey4, U. Bangert4, A. Kumar1, Ra.G.P. McQuaid1, J.M. Gregg1, 1Centre for Nanostructured Media, School of Mathematics and Physics, Queen’s University Belfast, Belfast, UK; 2School of Science and Engineering, University of Dundee, Dundee, UK; 3Department of Materials, Imperial College London, London, UK; 4Department of Physics, School of Sciences and Bernal Institute, University of Limerick, Limerick, Ireland
Negative capacitance has attracted a lot of attention recently thanks to its potential to enable shorter switching time of transistors. It has been observed in systems as diverse as p-n junction, electrochemical systems, and ferroelectrics superlattices. In this work, we show that regions in a boracite crystal (Cu3B7O13Cl) exhibit anomalous electric-field-induced movement of charged domain walls, consistent with negative capacitance in this region. Indeed, in this boracite, regions with polarisation aligned against the field coarsen at the expense of those aligned with the field; this anomalous movement lead to an increase in the global electrostatic energy and the negative capacitance behaviour. After presenting evidence for the correct attribution of the nature of the domains, relying on several scanning probe techniques, the classical and anomalous motion of domain walls in Cu-Cl boracite studied through optical microscopy will be presented. Indeed, we observed that polarisation-field (P-E) hysteresis loops, inferred from optical imaging, show negative gradients and hence non-transient negative capacitance, throughout the P-E cycle. Using Charge Gradient Microscopy (CGM) and Kelvin Probe Force Microscopy (KPFM), we confirm that the switching current associated with this anomalous motion is indeed opposite to what would be expected in ferroelectric switching and that the local electric field is aligned with the macroscopic electric field, contrarily to all observation of negative capacitance in ferroelectrics. Hence, the observation of negative capacitance in Cu-Cl boracite is unique.
CI-1:L06 Unexpected Electrical Breakdown Processes in Metal-Aluminumoxide-Metal Structures
H. KLIEM, K. Faliya, Institute of Electrical Engineering Physics, Saarland University, Saarbruecken, Germany
Metal-aluminumoxide-metal structures are prepared by PVD on Si-wafers. Their breakdown properties are investigated. On the Si a Cu/Al bottom electrode with 600nm/60nm thickness is evaporated. Using ceramic powder the aluminumoxide film, thickness 200nm, is prepared by electron beam evaporation. Cu and Pd top electrodes with different diameters complete the structure. A ramp voltage is applied. Before final breakdown at about 4.5 MV/cm appears, single partial breakdown spots are visible on the top electrode in fields above 1MV/cm. On Pd electrodes the spot density is 4 times higher than at Cu electrodes. On the top the spot's diameter is about 20µm. The spots form craters as deep as 1.5µm.They penetrate the bottom electrode and reach into the Si substrate. With the crater's volume and the specific heats of the materials the energy necessary to form the craters by melting or evaporation can be calculated. This energy is compared to the structure's electrostatic energy at the spot voltage: the electrostatic energy is up to 50 times smaller than the energy necessary to melt the material and 350 times smaller than the energy for evaporation. The hot plasma of the breakdown channel in the oxide seems to trigger an unknown process, which delivers the energy required to form the craters.
CI-1:IL08 The Tuning of the Ferromagetic Resonance of SrZ Hexaferrite with an External Magnetic Field
F.E. Carvalho1, A.C.C. Migliano1, M.R. Silva2, J.C.S. Amaral3, R.C. Pullar3, 4, 1Instituto de Estudos Avançados / Instituto Tecnológico da Aeronáutica, Brazil; 2Universidade Federal de Itajubá, Brazil; 3Dept. Eng. de Materiais e Cerâmica & Dept. Física, Universidade de Aveiro, Portugal; 4Dipartimento di Scienze Molecolari e Nanosistemi (DSMN), Università Ca' Foscari Venezia, Venezia Mestre, Venezia, Italy
The hexagonal Z-type ferrite Sr3Co2Fe24O41 (SrZ), first synthesised by Pullar et al. in 2001, was famously reported by Kitagawa et al. as being a room temperature multiferroic material in 2010. Since then, there have been detailed investigations into its multiferroic properties, but little into its high frequency and microwave properties, and ferromagnetic resonance frequency (FMR) which determines its ability as an electromagnetic (EM) absorber and radar absorbing (RAM) stealth material. We measured complex permeability and permittivity of a single phase polycrystalline ceramic sample of SrZ between 300 MHz - 8 GHz (X-band), showing a strong FMR at ~2.3 GHz. This FMR could also be tuned by the effect of an external magnetic field, by moving a simple bar magnet progressively closer to a toroidal sample. This incurred a very slight shift in the peak to 2.46 GHz at distances of 2.5-10 cm from the sample – a tuning of 5.7%, which is not insignificant. At a close distance of 0.5 mm we got a high degree of tuning of FMR to 3.4 GHz, a large change of 1.08 GHz = 31.8%. Such results have never been reported before, and are significant, as this would enable tuning of the FMR via simple physical movement of a bulk magnet, effectively creating a tuneable microwave filter or absorber.
CI-1:L10 Magnetodielectric and Electromagnetic Wave Absorption Properties of Ceramic Nanocomposites based on the Magnetically Soft, Semi-hard and Hard Ferrites
A. RADON, P. Wlodarczyk, L. Hawelek, M. Polak, A. Kolano-Burian, Łukasiewicz Research Network, Institute of Non-Ferrous Metals, Gliwice, Poland
Ferrites belong to the broad group of materials with interesting magneto-dielectric properties. Many of them, such as magnetite, are characterized by soft magnetic properties. However, there are also many semi-hard and hard magnetic ferrites such as CoFe2O4 and BaFe12O19, respectively. The possibility of synthesizing ferrites in the form of nanoparticles allows to applicate them in various fields, such as drug delivery platforms, catalysts, and high-frequency components (antenna substrates and microwave absorbers). In this study, the interaction between magnetically soft, semi-hard, and hard ferrites was described in the context of their electromagnetic (EM) wave absorption properties in the low-frequency range. While the EM wave absorption properties in the high-frequency range (above a few GHz) are well known, the interaction of the ferrites with EM waves in lower frequencies (below the 2 GHz range) is still not well described. Accordingly, the complex permittivity, permeability, and conductivity were determined using broadband dielectric spectroscopy in wide frequency and temperature range for core-shell-like ferrites and used to determine the complex absorption mechanism for various combinations of the CoFe2O4, Fe3O4, NiZnFe2O4, and BaFe12O19 ferrites.
CI-2:IL04 Strain Effect on Relaxor Ferroelectric Domains in Epitaxial 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3/SrRuO3 Heterostructures
M. SPREITZER1, J. Belhadi1, U. Gabor1, H. Uršič2, N. Daneu1, G. Koster1, 3, 1Advanced Materials Department, Jožef Stefan Institute, Ljubljana, Slovenia; 2Electronic Ceramics Department, Jožef Stefan Institute, Ljubljana, Slovenia; 3MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
Controlling the growth of complex relaxor ferroelectric thin films and understanding the relationship between biaxial strain-structural domain characteristics is desirable for designing materials with a high electromechanical response. Here, we used optimized growth parameters and target compositions to obtain epitaxial (40-45nm) 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3/(20nm)SrRuO3 (PMN-33PT/SRO) heterostructures using pulsed-laser deposition on SrTiO3 and ReScO3 substrates. Results confirmed high-quality and single-phase thin films with sharp interfaces, homogeneous strain and epitaxial cube-on-cube growth mode. We also observed that domain structure of the PMN-33PT heterostructures are sensitive to the applied compressive strain. From reciprocal space maps an evolution from butterfly-shaped diffraction pattern for mildly strained PMN-33PT layers, which is an evidence of stabilization of relaxor domains, to disc-shaped diffraction patterns for the high compressive strain with a highly distorted tetragonal structure, is observed. The piezoresponse force microscopy amplitude and phase of the PMN-33PT thin films confirmed the relaxor-like for a strain state below ~ 1.13% while for higher compressive strain (~ 1.9%) irregularly shaped and poled ferroelectric domains were observed.
CI-2:IL10 Local Structural Features and their Dynamics in Lead-Free Ferroelectrics at Atomic Scale
A. Bencan1,4, O. Condurache1,4, H. Ursic1,4, T. Rojac1,4, M. Komelj3, B. Dkhil5, A Bradesko5, D. Damjanovic6, G. Drazic2, 1Electronic Ceramics Department, Jozef Stefan Institute, Ljubljana, Slovenia; 2Department of Materials Chemistry, National Institute of Chemistry, Ljubljana, Slovenia; 3Department for Nanostructured Materials, Jozef Stefan Institute, Ljubljana, Slovenia; 4Jozef Stefan International Postgraduate School, Ljubljana, Slovenia; 5Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, Université Paris-Saclay, Gif-sur-Yvette, France; 6Group for Ferroelectrics and Functional Oxides, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Using scanning transmission electron microscopy - STEM we can resolve local structural features in ferroelectrics down to the atomic level. Furthermore, using in-situ biasing/heating holders, we can perform structural studies under external stimuli and take another step towards understanding the behaviour of ferroelectrics under dynamic conditions. In this talk, we will present cases of structural studies of lead-free ferroelectrics by STEM. We will show that we can directly visualize polar nano-clusters in the paraelectric phase of BaTiO3-based ceramics, which contribute to the material’s macroscopic polarization [Bencan et al., Nat. Comm. 2021]. We will also focus on the domain walls (DWs) in BiFeO3 and (K,Na)NbO3 and show that the point defects at the DWs in BiFeO3 ceramic make the walls electrically conductive, affect the DW width and the distribution of the lattice strain [Rojac et al., Nat. Mat. 2017, Bencan et al., Nat. Comm. 2020], and that the morphology of domains in BiFeO3 and (K,Na)NbO3 single crystals is complex. It ranges from the formation of step-like DWs to lamellar and zigzag walls with different mobility, reflecting in pinched and biased domain-area–voltage hysteresis reminiscent of those measured macroscopically as result of interactions with pinning centers.
CI-2:L13 Electrocaloric Effect of KTa0.65Nb0.35O3 / BaTiO3 Multilayer Thin Films prepared by sol-gel Method
Byeong-Jun Park, Dept. of Materials Engineering and Convergence Technology, RIGET, Gyeongsang National University, Jinju, South Korea
In this study, potassium tantalate niobate(KTN(65/35)) / barium titanate multilayer thin films on Pt/Ti/SiO2/Si substrates were prepared by the sol-gel process and the spin-coating method. Structural and electrical properties were measured according to the number of coatings, and the applicability for electrocaloric devices was investigated. For the first layer, KTN layer was dried at 200°C for 5 minutes, pyrolyzed at 400°C for 10 minutes and then, BT layer was coated on the KTN layer with the same conditions. These processes were repeated several times to obtain the desired thickness. Structural properties, such as XRD, SEM and ferroelectric properties such as hysteresis loop, polarization and ΔT were measured to investigate the electrocaloric effect of KTN/BT multilayer thin films.
CI-2:IL17 Sintering Strategies towards Piezoceramics and MEMS with Controlled Chemistry and Interfaces
C. ELISSALDE, U.C. Chung, I.M. Rua Taborda, M. Maglione, CNRS, Université de Bordeaux, ICMCB, Pessac, France; H. Debéda, A. Diop, B. Plano, Université de Bordeaux, Laboratoire IMS, Talence, France
Significant breakthroughs and developments have been recently achieved in the field of advanced and low temperature sintering processes. In particular, solvent-assisted processes and Field Assisted Sintering Technologies have allowed to face challenges in the search for functional materials and multimaterials while reducing environemental footprint [1]. Some illustrations will be given to highlight in particular, the potentiality of Spark Plasma Sintering (SPS) in terms of structure/microstructure control. In this context, the combination of SPS with printed technology offers an energy-efficient way towards low temperature manufacturing of ceramics for electronics. Such an approach dedicated here to the co-sintering of metal/ceramic multilayers allows a better control of the chemistry, interfaces and microstructure [2]. Here we focus on the densification of lead containing (Pb(ZrTi)O3) and Pb-free (KNa)NbO3 piezoelectric ceramics and printed layers on a metal substrate. The main challenge is to develop sintering strategies for low temperature processing of vibration energy harvesters using piezoelectric MEMS (MicroelectroMechanicaISystems).
[1] A. Ndayishimiye et al. J. Eur. Ceram. Soc. 40, 1312, 2020 [2] H. Debéda et al. Ceramics, 3, 453, 94, 2020
CI-2:L22 Dynamics of Ferroelectric Domain Walls in Bismuth Ferrite Observed by In-situ Voltage Biasing Transmission Electron Microscopy
O. Condurache1, 2, G. Dražić1, 2, 3, T. Rojac1, 2, H. Uršič1, 2, B. Dkhil4, A. Bradeško4, A. Benčan1,2, 1Electronic Ceramics Department, Jožef Stefan Institute, Ljubljana, Slovenia; 2Jožef Stefan International Postgraduate School, Ljubljana, Slovenia; 3Department of Materials Chemistry, National Institute of Chemistry, Ljubljana, Slovenia; 4Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, Université Paris-Saclay, Gif-sur-Yvette, France
Ferroelectric domain walls (DWs) are a few unit cells wide topological defects that separate regions with different polarization orientation. When a ferroelectric is under the influence of an external electric field, the dynamics of DWs is activated as a result of polarization switching. Therefore, it is believed that DWs have a great potential to play a key role in the development of future atomic-scale electronics [G.F. Nataf et al., Nature Reviews. Physics 2020]. However, gaining insight into the interaction of DWs with electric field has only recently emerged due to the exciting development of in-situ electric field techniques with atomic spatial resolution. Here, we investigate the dynamics of DWs in bulk BiFeO3 in real time by using atomic resolution scanning transmission electron microscopy in combination with dedicated in-situ voltage bias holder. We show that the DW mobility is dependent on their type and morphology. The influence of the electric field on the DWs is discussed in terms of unit cell distortion, local strain and Fe-atoms displacement relative to the Bi-sublattice. The aim was to bring the study of DWs closer to a scale which is directly relevant to the development of devices with low dimensionality.
CI-3:IL01 Designing Multiferroic Perovskite Oxides with Phase-Change Magnetoelectric Responses
H. Amorín, M. Algueró, J.A. Quintana-Cilleruelo, A. Castro, Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Cantoblanco, Madrid, Spain; C.M. Fernández-Posada, University of Cambridge, Downing Street, Cambridge, UK
Magnetoelectric multiferroics are compounds that combine ferroelectricity and magnetic orders, and that are liable to show coupling between electric polarization and magnetization. Research in this field is being driven toward novel approaches for obtaining compounds with large linear magnetoelectric effect or crossed switching phenomena at room temperature. There are two main areas of research: single-phase multiferroics and composite materials. In this talk, most promising single-phase approaches will be highlighted, specifically, perovskite-type oxide solid solutions and layer-structured Aurivillius phases. Recent works on perovskite systems chemically designed to be placed at instabilities involving multiferroic states for phase-change magnetoelectric responses will be reviewed (C.M. Fernández-Posada et al., Nature Comm. 2016, 7, 12772; Adv. Funct. Mater. 2018, 28, 1802338; J. Phys. Chem. C 2019, 123, 13063). Alternatively, magnetoelectric coupling by composite approaches will be also highlighted, specifically, those consisting of elastically-coupled high-sensitivity piezoelectric and magnetostrictive phases (H. Amorín et al., Sci. Technol. Adv. Mater. 2015, 16, 016001; ACS Appl. Mater. Interf. 2017, 9, 39094; J. Eur. Ceram. Soc. 2019, 39, 1065).
CI-3:IL02 Magnetization Reversal by Electric Field at Room Temperature in Co Substituted Bismuth Ferrite Thin Film
MASAKI AZUMA, K. Shigematsu, Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokoyama, Japan and Kanagawa Institute of Industrial Science and Technology, Ebina, Japan; K. Shimizu, K. Ozawa, M. Katsumata, Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokoyama, Japan; H. Hojo, Department of Energy and Material Science, Kyushu University, Fukuoka, Japan; K. Mibu, Nagoya Institute of Technology, Nagoya, Japan
Electric field manipulation of magnetization is intensively investigated because of potential application in low-power-consumption non-volatile magnetic memory devises. Ferroelectric BiFeO3 has a cycloidal space-modulated spin structure with a periodicity of 62 nm superimposed on the G-type antiferromagnetic structure. The presence of cycloidal ordering prohibits the appearance of net ferromagnetic magnetization due to spin canting and a linear magnetoelectric effect. We have observed a spin structure transition from low-temperature cycloidal one to high-temperature collinear one at ~200 K using Mössbauer spectroscopy in rhombohedral BiFe0.1Co0.9O3 thin films fabricated by PLD on SrTiO3 (STO) (111) substrate [1]. Spontaneous magnetization of 0.03 uB/f.u. confined in a magnetic easy plane perpendicular to the electric polarization is generated by Dzyaloshinskii-Moriya interaction. Films fabricated on GdScO3 (110) substrate has out-of-plane component of magnetization which can be observed by MFM. It is demonstrated that the out-of-plane magnetization can be reversed by electric polarization reversal using PFM at room temperature [2, 3].
[1] H. Hojo, et al., Adv. Mater, 29, 160313 (2017). [2] K. Shimizu, et al., Nano Letters, 19, 1767 (2019). [3] M. Katsumata, et al., Appl. Phys.
CI-3:IL03 Magnetoelectric Ceramic Layered Composites: Causes behind Variability beyond Interface Quality
M. ALGUERO, H. Amorín, A. Castro, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Cantoblanco, Madrid, Spain; P. Ramos, Departamento de Electrónica, Universidad de Alcalá, Alcalá de Henares, Spain; R. Moreno, Instituto de Cerámica y Vidrio (ICV-CSIC), Cantoblanco, Madrid, Spain; M. Venet, Departamento de Física, Universidade Federal de São Carlos, São Carlos, SP, Brazil
Magnetoelectric composites are key enabling materials for a range of proposed, novel related technologies like room-temperature-operation high-sensitivity magnetic field sensors, electrically-tunable magnetic microwave components, and wireless powering of bioimplanted devices or sensor networks to name but a few. Among the different approaches under development, cofired ceramic composites of ferroelectric perovskite and ferrimagnetic spinel oxides are especially suitable for up-scaling and miniaturization. We update here our current research on ceramic layered composites. This geometry is widely acknowledged to provide the largest magnetoelectric coefficients and improved reliability, though knowledge of the factors determining response is incomplete. As a result, reported coefficients suffer from significant variability, and high figures are not easily reproduced. In this communication, based on our results for two material systems, namely Bi0.36Pb0.64Sc0.36Ti0.64O3-NiFe2O4 and (K0.5Na0.5)1-xLixNb1-yTayO3/CoFe2-zMzO4 (M: Ga or Mn), and for layered composites with tailored interfaces and varying geometry, including multilayer structures prepared by tape casting, and helped by simulation with finite element analysis, several causes behind variability are discussed.
CI-4:IL01 Doping and Defects in Oxide Semiconductors
A. Janotti, University of Delaware, Department of Materials Science and Engineering, Newark, DE, USA
Oxides are key materials for many aplications, from (photo)catalysis to transparent conductors to memristors. In all these applications, intrinsic defects, impurities, and charge localization play major role in the materials performance. Point defects such as oxygen vacancies have often been invoked to explain many of the observed phenomena in oxides. Still, direct identification of point defects in these materials remains elusive, and proof of their existence has not been unambiguous. First-principles calculations based on the density functional theory have emerged as a powerful tool to study defects in crystals, and hybrid functional implementations have provided unprecedented accuracy in the description of point defects in semiconductors and insulators, and their impact on materials properties. These calculations often provide information that are difficult to access experimentally. In this presentation we will discuss recent studies of point defects and impurities in prototype wide-band-gap oxides, such as ZnO, TiO2, SrTiO3 and Ga2O3. We will draw comparisons and provide a broad picture of defect formation and stability in the different materials. We will also interpret some key experimental observations in light of first-principles results.
CI-4:IL03 Development of Lithium Conducting Oxides from Crystal Chemistry to Solid-state Batteries
E.J. CUSSEN, Department of Materials Science and Engineering, The University of Sheffield, UK
Solid state electrolytes for use in all solid-state batteries face demanding performance criteria. They must conduct Li+ ions between electrodes during battery cycling and withstand the electrical and chemical potentials in the cell, all whilst maintaining stable interfaces as electrode materials (de-)swell during lithium (de-)intercalation and redox. We have developed various fast-ion conducting phases for this purpose from the garnet, NASICON and perovskite structural families. These materials are characterised using combinations of crystallographic and local structural probes using both X-ray and neutron scattering, and lattice dynamics are measured by complementing impedance analysis with muon spin relaxation measurements. Deployment of these electrolytes in all solid-state batteries requires matching of electrolyte properties with cathode and anode materials. Our approach is to chemically tune the material’s functionality and so form electrolyte and electrode combinations from a common structure type. This can be achieved with minimal change in chemical composition such the LiM2(PO4)3 phases that form electrolyte (M = Zr) and electrode (M = Ti) materials. We will present examples of similar lattice matching for electrochemical performance from each structural family.