Die Bedeutung von keramischen Materialien mit funktionalen Eigenschaften ist über die letzten Jahrzehnte kontinuierlich gestiegen. Ein besonderes Interesse liegt dabei in der elektronischen Speicherung von Informationen. Die Realisierung war jedoch lange Zeit problematisch, da die erforderlichen Feldstärken, die notwendig sind, um die Polarisation zu schalten, für Massivmaterialien zu hoch sind. Heutzutage ist dies dank moderner Dünnschichttechnologien kein Problem mehr, so dass nichtflüchtige ferroelektrische Datenspeicher kommerziell verfügbar sind. Aufgrund der ausgezeichneten dielektrischen und elektromechanischen Eigenschaften von ferroelektrischen Materialien werden diese auch für Anwendungen in Aktuatoren, Kondensatoren oder mikro-elektro-mechanischen Systemen verwendet. Neben den klassischen Ferroelektrika wie Pb(Zr,Ti)O3 spielen dabei vor allem Relaxor-Ferroelektrika wie Pb(Mg1/3Nb2/3O3-PbTiO3 (PMN-PT) eine entscheidende Rolle. Eine weitere sehr interessante funktionale Eigenschaft von ferroelektrischen Materialien, die besonders in den letzten zehn Jahren das Forschungsinteresse geweckt hat, ist der elektrokalorische Effekt (electro caloric effect, ECE). Besonders hohe ECE konnten in der Vergangenheit mit Blei-basierenden Materialien, wie beispielsweise PMN-PT, erzielt werden. Um den Einfluss der Struktur auf die funktionalen Eigenschaften zu untersuchen ist es vorteilhaft, mit texturierten Schichten zu arbeiten. Als Materialsystem wurde in dieser Arbeit PMN-PT verwendet, da dieses besonders gute ferroelektrische und elektrokalorischen Eigenschaften zeigt und es aufgrund der vielfältigen veröffentlichten Untersuchungen als Modellsystem genutzt werden kann. Als geeignete Herstellungsmethode von Dünnschichten komplexer Oxide hat sich die gepulste Laserabscheidung herausgestellt, die auch in dieser Arbeit genutzt wurde. Die Schwerpunkte der strukturellen Untersuchungen beschäftigen sich mit der Stabilisierung der Perowskit-Phase des PMN-PT, der detaillierten Aufklärung des Gefüges sowie der Realisierung von Schichten mit unterschiedlicher Orientierung und auf verschiedenen Substratmaterialien. Hinsichtlich der funktionalen Eigenschaften wird auf den Einfluss der Pyrochlor-Phase auf die Ferroelektrizität, die Anisotropie der ferroelektrischen und elektrokalorischen Eigenschaften sowie auf eine Möglichkeit der direkten Messung der elektrokalorischen Temperaturänderung von PMN-PT Dünnschichten eingegangen.

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Abstract In this thesis, dielectric and thermal behaviours due to the application of an electric field were studied in relaxor ferroelectric (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and (1−x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) systems of great technological importance. Special attention was given to the behaviour of the electric-field-induced phase transitions and electrocaloric effect, which are closely related to the existing and potential applications. Reactive sintering or columbite methods were used to fabricate polycrystalline PMN-PT ceramics with various compositions (x=0−0.3). In addition, commercial PMN-PT single crystals with composition close to the morphotropic phase boundary region were used. A studied PZN-PT crystal composition was grown by solution gradient cooling technique. Materials were mainly studied by means of dielectric and direct temperature measurements. The electrocaloric effect observed in a ceramic PMN-PT system was found to show distinct maximum values close to the thermal depolarization temperatures with low electric fields. The temperature range and magnitude of the electrocaloric effect was significantly expanded to high temperatures with increasing electric fields due to the contribution of polar nanoregions. The maximum electrocaloric temperature change was in the range of 0.77−1.55 °C under an electric field of 50 kV/cm. In addition, temperature change measurements on depoled PMN-0.13PT ceramics demonstrated that the electrocaloric effect is accompanied with an irreversible part below its depolarization temperature due to hysteresis loss and a possible phase transition type response related to the evolution of the macroscopic polarization. An electric field application to the <001> and <011> directions in PMN-PT crystals was found to cause distinct anomalies in the dielectric and temperature change responses. These anomalies were attributed to the complex polarization rotation routes and different phase stability regions in the electric-field-temperature phase diagrams of PMN-PT. Furthermore, measurements on PMN-PT crystals provided the first direct indications of a temporarily reversed electrocaloric effect with an increasing electric field. In addition, the measured electrocaloric trends in PZN-PT crystal were reproduced by a simple lattice model and mean-field approximation around the transition temperature. This demonstrated that the electrocaloric effect is driven mainly by the dipolar entropy lowering. / Tiivistelmä Tässä työssä tutkittiin dielektristen ominaisuuksien ja lämpötilan käyttäytymistä teknologisesti merkittävissä (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) ja (1−x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) ferrosähköisissä relaksorimateriaaleissa sähkökentän vaikutuksen alaisena. Tutkimuksen erityishuomion kohteena olivat sähköisesti indusoidut faasimuutokset sekä sähkökalorinen ilmiö, jotka liittyvät läheisesti nykyisiin sekä tulevaisuuden sovellutuksiin. Monikiteisiä PMN-PT keraamikoostumuksia (x=0−0,3) valmistettiin sekä reaktiivisella sintrauksella että kolumbiittimenetelmällä. Lisäksi tutkimuksessa käytettiin kaupallisia PMN-PT erilliskiteitä, joiden koostumus on lähellä morfotrooppista faasirajaa. Työssä käytetty PZN-PT erilliskide kasvatettiin jäähdyttämällä korkean lämpötilan liuoksesta. Materiaaleja tutkittiin pääosin lämpötilan ja dielektristen ominaisuuksien mittauksilla. Kun PMN-PT keraamisysteemiin kohdistettiin alhainen sähkökenttä, sähkökalorisen ilmiön selkeä maksimiarvo havaittiin lähellä materiaalin termistä depolarisaatiolämpötilaa. Suuremmilla sähkökentän arvoilla sähkökalorinen ilmiö voimistui ja sen lämpötila-alue laajeni korkeampiin lämpötiloihin polaaristen nanoalueiden kytkeytymisen vuoksi. Sähkökalorisen lämpötilamuutoksen maksimi vaihteli välillä 0,77−1,55 °C sähkökentän arvolla 50 kV/cm. Lisäksi lämpötilamittaukset depoolatulle PMN-0,13PT koostumukselle osoittivat, että sähkökalorisen ilmiön ohella materiaalissa esiintyy makroskooppisen polarisaation muodostumiseen liittyvä palautumaton lämpöenergia depolarisaatiolämpötilaa pienemmissä lämpötiloissa hystereesihäviön ja mahdollisen faasimuutoksen vaikutuksesta. PMN-PT erilliskiteiden dielektrisyys- ja lämpötilavasteessa havaittiin selkeitä muutoksia sähkökentän vaikuttaessa <001> ja <011> kidesuuntiin. Nämä muutokset ovat selitettävissä PMN-PT:n polarisaation kompleksisten rotaatiosuuntien ja erityyppisten sähkökenttä-lämpötila -faasidiagrammien stabiilisuusalueiden avulla. PMN-PT kiteiden mittauksissa havaittiin myös ensimmäinen suora osoitus väliaikaisesti käänteisestä sähkökalorisesta ilmiöstä sähkökentän kasvaessa. Lisäksi mitatut PZN-PT erilliskiteen sähkökaloriset ominaisuudet transitiolämpötilan läheisyydessä pystyttiin pääpiirteittäin mallintamaan käyttämällä yksinkertaista hilamallia ja keskimääräisen kentän approksimaatiota. Mallinnuksen mukaan sähkökalorinen ilmiö aiheutuu pääasiassa sähköisesti indusoidusta dipolientropian alenemisesta.

Ce travail propose l’utilisation d’un nouveau matériau, appelé PMN-PT, qui continue aider la miniaturisation des systèmes complexes, utilisés dans des différentes technologies. Le travail est présenté dans le cadre de collaboration entre deux projets, MIOP et ADMAN. Les besoins tient compte que les actionneurs soient capables de délivrer de haute déplacement tout en conservant la simplicité et la fiabilité du système. L’accent est mis sur la polyvalence de ce matériau piézo-électrique, PMN-PT, en raison de ses propriétés électro-mécanique. Le travail comprend un aperçu sur quoi influence les propriétés électro-mécaniques du PMN-PT. L’accent est mis sur deux différentes, mais très puissants coupes: anisotrope [011] et longitudinale [001], choisi pour grand déplacement et haute dynamique avec un volume petit. Pour le PMN-PT[001], une structure de type poutre a été étudié, avec un modèle amélioré pour prendre en compte les spécificités de matériel. Les déplacements et forces ont été trouvés d’ être supérieur `a un actionneur en PZT, similairement dimensionnée, tandis que avoir des non-linéarités réduites. Ceci est illustré avec une micro pince avec 6DDL. L’étude de PMN-PT [001] coupé longitudinal suit. Cette étude a été fait en utilisant PMNPT comme un actionneur avec une structure simple, facile à intégrer. Les résultats démontrent les améliorations PMN-PT peut apporter à micro-spectrométrie et la correction d’image avec des micromiroirmobiles. Un micro actionneur PMN-PT a été intégré dans une structure compatible avec des MOEMS et présenté. / This work proposes the use of a novel material, called PMN-PT, that futher aids the miniaturizationof complex systems used in different technologies. The work is presented within the collaborativeframework of two projects, MIOP and ADMAN. The end-needs account for actuators capable ofdelivering high displacement, while maintaining system simplicity and reliability. The focus is onthe versatility of the PMN-PT piezoelectric material, due to its electro-mechanical properties. Thework includes an overview on what influences the electro-mechanical properties focusing on twodifferent, though very potent cuts: anisotropic [011] and longitudinal [001]. They were chosen forgenerating large displacement and high dynamics with small volume. For PMN-PT[001] a cantileverstructure was studied, for which the model was improved taking into account the material specificities.Displacements and forces were found to be superior to a similarly dimensioned PZT actuator, whilsthaving reduced non-linearities. This is exemplified with a 6 DoF capable microgripper. The PMNPT[001] longitudinal cut based actuator study follows. This is done by using PMN-PT as a simple,easy to integrate, bulk actuator. The findings demonstrate the improvements PMN-PT can bringto micro-spectrometry and image correction with micro-mirror displacement. A bulk PMN-PT microactuator was integrated into a MOEMS compatible structure and presented.

Cathelicidins are cationic host defence peptides (CHDP) with essential roles in the innate defence system. These peptides have antimicrobial potential and the capacity to modulate innate immunity and inflammatory processes. Neutrophils (PMN) are the main reservoir of cathelicidins and play key roles in first line defence against infection. The appropriate regulation of PMN function, death, and clearance is critical to innate immunity, and the efferocytosis of apoptotic PMN, in contrast to necrotic cells, is proposed to promote the resolution of inflammation. In this thesis I demonstrate that the human cathelicidin LL-37 rapidly induced secondary necrosis of apoptotic human PMN and identify the essential C-terminal region of LL-37 required for this activity. In addition to the induction of secondary necrosis, higher concentrations of LL-37 also promoted PMN granule contents release. LL-37-induced secondary necrosis did not affect PMN ingestion by human monocyte-derived macrophages and, in contrast to expectation, was not proinflammatory. Interestingly, the anti-inflammatory effects of apoptotic PMN on activated macrophages were retained and even potentiated where LL-37-mediated secondary necrosis induced anti-inflammatory granule content release. Consistent with the results of in vitro studies, in vivo murine sterile peritonitis model revealed the same phenomenon: LL-37-induced secondary necrosis diminished inflammatory responses with decreased PMN influx. I also present data on LL-37- mediated modulation of innate immune effector cell cytokines responses to inflammatory signals. I propose that during acute inflammation LL-37 can modulate innate immune responses through its activity on cytokine production, and that LL-37-mediated secondary necrosis of apoptotic PMN has anti-inflammatory effects, but may also mediate host damage by promoting the release of potentially harmful intracellular contents under chronic or dysregulated conditions.

Background: Patients with burns are susceptible to organ failure, and there is indirect evidence that leukocytes may contribute to this process. They may change the expression of cell-surface receptors after certain stimuli, for example, the burn. We therefore aimed to assess the changes induced by the burn in the expression of leukocyte cell-surface receptors CD11b, CD14, CD16, and CD62L on the surface of PMNs and monocytes. We also wanted to examine the dynamics of this activation during the first week after the burn, and to relate it to the size of the injury. Methods: Ten patients with burns of andgt;15% (TBSA) were included in the study. Blood samples were collected on arrival and every consecutive morning during the first week. Healthy volunteers acted as controls. Results: PMN CD11b expression was increased. The extent of PMN CD11b expression correlated negatively to the size of the full thickness burn. Monocyte CD14 expression increased initially but there was no relation to the size of the burn. PMN CD16 expression decreased initially during the first days and the decrease was related to burn size. CD62L did not vary depending on the burn in either PMN or monocytes during the first week after the burn. Conclusion: This study showed that specific receptors on the surface of leukocytes (PMN CD11b, monocyte CD14 and PMN CD16) are affected by the burn. Expression of PMN CD11b and CD16 are related to burn size. Burn-induced effects on the expression of PMN receptors, such as PMN CD11b and CD16, may contribute to burn-induced infection susceptibility. / Original Publication: Joakim Johansson, Florence Sjögren, Mikael Bodelsson and Folke Sjöberg, Dynamics of leukocyte receptors after severe burns: An exploratory study, 2011, BURNS, (37), 2, 227-233. http://dx.doi.org/10.1016/j.burns.2010.08.015 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

Relaxor ferroelectric PZN-xPT and PMN-xPT single crystals exhibit extraordinary electromechanical properties. They are under development for applications in sensors, actuators and transducers. The polarization switching and phase transition behavior of PZN-4.5%PT and PMN-32%PT single crystals under external loading has been investigated. Experimental investigation elucidates the polarization switching and phase transition behavior of relaxor ferroelectric crystals at different orientation cuts under combined temperature, electric field and stress loading. These crystals exhibit strong orientation dependence of electromechanical properties, and the applied fields all affect the poling and phase states of the crystals. Based on experimental investigation, crystal variant modeling was developed to compute the piezoelectric properties of multi-domain crystals at different orientation cuts from a set of properties for the single domain. Thermodynamics and work-energy analysis of field induced phase transitions in these single crystals sheds light on the phase transition mechanism of ferroelectric crystals. Fracture behavior of relaxor single crystals under non-uniform electric fields at a partial electrode edge has also been measured and analyzed.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-13Bitstream added on 2014-06-13T19:53:26Z : No. of bitstreams: 1 felix_aa_me_ilha.pdf: 3988287 bytes, checksum: d87d85fca7e813d5a8e3850d61c9c14e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho descreve os estudos realizados para a síntese de filmes ferroelétricos ultrafinos de Pb(Mg1/3Nb2/3)O3 (PMN) e o estudo sistemático da cinética de cristalização deste material visando a obtenção de filmes monofásicos. Os filmes foram produzidos a partir da modificação de um método químico baseado em precursores óxidos. A obtenção dos filmes de PMN se deu através de uma técnica de duplo estágio, que possibilita maior controle na supressão de fases pirocloro, e da técnica via Método dos Precursores Óxidos (MPO), através da reação direta dos óxidos. Filmes de PMN foram preparados sobre substratos Si(100) com diferentes números de deposições. Esses filmes foram submetidos a tratamentos térmicos entre 400oC e 800ºC, em forno convencional, sob diferentes condições de preparo. A estrutura dos filmes foi investigada pela técnica de difração de raios-X e refinamentos da estrutura pelo método de Rietveld. Os resultados apresentaram uma coexistência da fase pirocloro Pb1.86Mg0.24Nb1.76O6.5 e da fase perovskita Pb(Mg1/3Nb2/3)O3 (PMN) nos filmes preparados via rota da Columbita e a supressão da fase prirocloro nos filmes preparados pelo método MPO. Um estudo da morfologia por MEV indicou a preparação de filmes com boa homogeinidade e espessura média de 150nm Os resultados obtidos neste projeto indicam que a estabilização da fase perovkita do PMN e a supressão da fase pirocloro está relacionada a uma combinação particular de parâmetros tais como tempo e temperatura de cristalização e a adição de excessos de MgO e PbO a estequiometria. / The present work describes the studies for the synthesis of ultrathin ferroelectric films of Pb(Mg1/3Nb2/3)O3 (PMN) and the systematic study of the crystallization kinetics of this material aimed at obtaining singlephase films. The films were produced from the modification of a chemical method based on oxide precursors. The obtention of the PMN films made by a technique of double stage, that allows greater control in the suppression of pyrochlore phases, and by technique via Oxide Precursors Method(OPM), through a direct reaction of the oxides. PMN films were prepared on Si(100) substrates with different numbers of depositions. These films were subjected to thermal treatments between 400ºC and 800°C, in conventional oven, under different preparation conditions. The structure of the films was investigated by the technique of X-ray diffraction and the structures refinements by the Rietveld method. The results showed a coexistence of pyrochlore phase Pb1.86Mg0.24Nb1.76O6.5 and perovskite phase Pb(Mg1/3Nb2/3)O3(PMN) in the films prepared via Columbita route and suppression of pyrochlore phase in films prepared by the OPM method. A study of morphology by SEM indicated the preparation of films with good homogeneity and medium thickness of 150 nm. The results obtained in this project suggest that the stabilization of PMN phase perovkite and the suppression of the pyrochlore phase is related to a particular combination of parameters such as time and temperature of crystallization and the addition of excess of MgO and PbO in the stoichiometry.

Clear speech is a speaking style that has been shown to improve intelligibility in adverse listening conditions, for various listener and talker populations. Clear-speech phonetic enhancements include a slowed speech rate, expanded vowel space, and expanded pitch range. Although clear-speech phonetic enhancements have been demonstrated across a variety of talkers, only a subset of these changes may be required for listeners to benefit perceptually from clear speech. Furthermore, while current literature has provided some understanding of the phonetic enhancements that are typical of clear speech and the improvements in intelligibility resulting from its use, less is understood regarding how listeners benefit from clear speech. Understanding the mechanisms underlying the effectiveness of clear speech will provide insight into speech processing more generally. To that end, two studies were conducted to investigate the possible mechanisms underlying clear-speech benefits. The first study tests the hypothesis that clear speech reduces the amount of information needed for syllable identification. The amount of information presented to listeners was controlled using a silent-center syllable paradigm, in which various amounts of the center or edge of the syllables were removed. The second study tests the hypothesis that phonetic processing of clear speech requires fewer neuro-cognitive resources than typical, or conversational, speech. An Event Related Potential (ERP) paradigm, focused on the Phonological Mismatch Negativity (PMN) component, was used to compare participants’ neurophysiological responses to conversational- and clear-speech stimuli. Results from the first experiment supported the hypothesis of a clear-speech benefit in partial syllables, although the effect was stronger for some vowels than for others. The second experiment demonstrated differences in the way the brain responds to clear versus conversational speech, for syllables in which only the nucleus varied across stimuli. Match-mismatch differences were found in the MMN and PMN components, while the N600 component was found to respond to style differences.