Universiẗat, Diss., 2006--Kassel. / Download lizenzpflichtig.

Techn. University, Diss., 2006--Darmstadt.

Zugl.: Kassel, Univ., Diss., 2006 / Download lizenzpflichtig

The first chapter introduces the basic principles governing the phenomenon like ferroelectricity, piezoelectricity and pyroelectricity, which influences the material properties for its device applications. An effort is made to examine the present status of material issues, measurement techniques and applications pertaining to the lead based PZT type systems. This chapter also highlights the objectives and the scope of work. The second chapter deals with the various basic experimental techniques and principles adopted for the synthesis and characterizations of materials which include phase and quantitative analysis by X-ray diffraction, density measurements, microstructures by scanning electron microscopy, electrical properties such as dielectric permittivity, dielectric loss, and piezoelectricity by impedance analyzer and piezometer etc. The materials were synthesized via two step solid state reaction by adopting a low temperature calcinations route. Further, hot processing was employed for densification and better control of microstructure of the ceramics. In the third chapter PZT1-x –PZNx (x=0, 0.1, 0.2 & 0.3) compositions prepared by the single step low temperature calcination method have been described. It is seen that the pyrochlore free perovskite phase could be obtained up to x=0.2 compositions. The effect of additives like Li and Mn on the structure, sinterability, microstructure, density and dielectric properties has been investigated. The improvement in densification and ferroelectric properties were observed for Li addition favor tetragonal phase while Mn addition compositions were inclined to pseudocubic phase. Further, the addition of Mn led to the significant decrease in Tc than the parent compositions compared to Li added compositions. In the fourth chapter, the X-ray diffraction data on pbzrx Ti1-x O3 (PZT) for x=0.48 to 0.52 are presented. High resolution x-ray studies for composition x=0.5 show the MPB which consists of monoclinic Zr rich studies and tetragonal Ti rich phase at room temperature. The refined structural parameters for MPB compositions have been obtained using least square Rietveld refinement program, FULLPROF 2006. The evolutions of lattice parameters of the system were also studied with respect to the temperature. The phase transformation in the system has been analyzed by x-ray diffraction pattern and dielectric measurements. The monoclinic phase transforms to tetragonal phase at 270oC after which the tetragonal phase transforms to paraelectric cubic phase at 370DoC. Dielectric properties show signature of the phase transformation. Hence, it is concluded to pole the MPB samples below 270o C to gain the advantage of increased ease of polarization reorientation for monoclinic phase. The fifth chapter deals with the systematic structural investigation on PZT1-y-PNZy (PZT-PNZ) and PZT1-y-PMNy (PZT-PMN) systems. In this chapter, an effort has been made to determine quantitatively the MPB phase contents and variation in Zr/Ti ratio of PZT-PZN and PZT-PMN systems. High resolution XRD data has been used for quantitative phase analysis using FULLPROF 2006. The correlation between the width of MPB and grain size has also been discussed for these systems. It is found that the addition of PMN and PZN to PZT system shifts the MPB towards pbZrO3 (PZ). The MPB can be regained by tuning the Zr/Ti ratio in the system. Further, there exists an inverse relation between the grain size and coexistence region in the system. It is seen that the MPB range is from x=0.48 to 0.58 and x=0.44 to 0.58 for 10% and 20% PZN concentration respectively. Similar trend has been obtained for the PZT-PMN system. The MPB ranges from x=0.46 to 0.53 and x=0.42 to 0.50 for 10% and 20% PMN respectively. The broadening of coexistence width is attributed to the lower grain size of our samples synthesized by adopting low temperature calcinations route. The sixth chapter deals with the hot pressing technique employed (adopting low temperature calcinations) for the synthesis of various PZT-PMN compositions with an intention of obtaining highly dense piezoceramics with fine, homogeneous and uniform microstructure. It also describes the dielectric, pyroelecrtic and pi ezoelectric properties were enhanced by hot processing technique. Li and Mn addition further improved the properties of the system. The seventh chapter investigates various nominal compositions of PZT-(Li, Nb) compositions based on certain assumptions. The attempt was made to introduce Li at A site and B site of ABO3 perovskite lattice. The ball milled, calcined powders were densified at<1000oC using hot pressing technique to prevent Li and Pb loss. High density ceramics have been studied for structural, dielectric, piezoelectric and pyroelectric properties. Through the clear cut evidence for the identification of Li site in the PZT system could not be established but the system which were synthesized under the assumption that Li substitutes A-site of the perovskite, favored the tetragonal phase and led to the enhancement in the dielectric, pyroelectric and piezoelectric properties. Further, their transition temperature was higher compared to the compositions where Li was tried to substitute B-site, which makes them promising candidates for transducer applications. The key finding in this thesis has been carried out by the candidate as part of the ph. D. programme. She hopes that this would constitute a worthwhile contribution towards the understanding of the behavior of lead based perovskites and in tailoring the properties of these ceramics towards device applications by the introduction of suitable additives in the system.

Les particules fines ont un impact réel sur la qualité de vie et la santé de millions de personnes dans les grandes zones urbaines, notamment en Asie. Pour les détecter et quantifier leur concentration, les capteurs de particules optiques sont les plus couramment étudiés, mais restent relativement chers et volumineux. Les transducteurs MEMS micropoutres sont largement utilisés pour des applications gravimétriques, pour la détection de particules ou de gaz, ce qui requiert des sensibilités massiques (Sm) élevées et des limites de détection (LOD) basses. Pour cela les micropoutres les plus adaptées sont celles ayant des fréquences de résonance (f0) et facteurs de qualité (Q) élevés, avec de faibles bruits de mesure et des masses faibles. Les micropoutres silicium sont couramment utilisées en tant que capteurs gravimétriques et sont de sérieux candidats pour répondre aux caractéristiques souhaitées. Cependant, la sérigraphie a le potentiel pour une fabrication moins chère, plus rapide et aussi à grande échelle. Pour ces micropoutres, l'actionnement et la lecture de f0 sont possibles par effet piézoélectrique. Bien qu'il existe des solutions inorganiques prometteuses sans plomb, les céramiques de titano-zirconate de plomb (PZT) possèdent encore les meilleures propriétés parmi les matériaux piézoélectriques. Des micropoutres fabriquées en technologie hybride couches épaisses sérigraphiées, à actionnement et lecture piézoélectriques intégrés, libérées à l'aide d'une couche sacrificielle polyester et avec co-cuisson de toutes les couches pour leurs libérations sont présentées ici. Différentes géométries ont été testées de 1 mm à 2 mm de large et de 1 mm à 8 mm de long, pour une épaisseur d'environ 100 μm. Une masse volumique ρ PZT = 7200 kg/m³ a été obtenue (≈ 93%ρ PZT massif). Enfin, avec une micropoutre 1×2×0,1 mm³, une sensibilité Sm ≈ 85 Hz/μm et une LOD de 70 ng ont été trouvées, permettant des applications en détection de particules. / Fine particulate matters (PM) have a real impact on the quality of life and health of millions of people in large urban areas, especially in Asia. In order to detect them and quantify their concentration, optical PM sensors are the most widely studied, but remain relatively expensive and bulky. MEMS microcantilever transducers are widely used for gravimetric applications, for PM or gas detection, which requires high mass sensitivities (Sm) and low limits of detection (LOD). A solution is to focus on microcantilevers with high resonance frequencies (f0) and quality factors (Q), low measurement noise and low masses. Silicon microcantilevers are commonly used as gravimetric sensors and are serious candidates to meet the desired characteristics. However, screen printing has the potential for cheaper, faster and large scale manufacturing. Such microcantilevers can be actuated and f0 read-out using the piezoelectric effect. Although promising lead-free inorganic solutions exist, titanium lead zirconate (PZT) ceramics still have the best properties among piezoelectric materials. Screen-printed microcantilevers manufactured in hybrid thick-film technology, with integrated piezoelectric actuation and read-out, released using a polyester sacrificial layer and with co-firing of all the layers are presented here. Different geometries were tested from 1 mm to 2 mm wide and from 1 mm to 8 mm long, for a thickness of about 100 μm. A density ρ PZT = 7200 kg/m³ (≈ 93%ρ PZT bulk) was obtained. With a 1×2×0.1 mm³ microcantilever, a sensitivity Sm ≈ 85 Hz/μm and a LOD of 70 ng were found, compatible with applications in PM mass detection.

Les zirconates titanates de plomb (PZT) suscitent un intérêt considérable pour plusieurs applications industrielles, au regard de leurs excellentes propriétés piézoélectriques et électromécaniques. Le contexte actuel de l’innovation technologique est la miniaturisation et l’allègement des produits ; c’est pour cette raison que de nombreuses études sont menées depuis une vingtaine d’années sur les techniques et les procédés de synthèse de ces matériaux piézoélectriques sous forme de couches minces tout en garantissant une fiabilité accrue. Dans ce contexte, l’étude menée dans le cadre de cette thèse, a visé l’optimisation du procédé d’élaboration de films minces piézoélectriques de PZT par pulvérisation cathodique magnétron en mode DC et en mode Rf, en vue d’obtenir des capteurs d’efforts piézoélectriques. La synthèse in situ et la cristallisation ex-situ des films élaborés, par recuit classique (CFA) ou recuit rapide (RTA) confirme une structure pérovskite du PZT, complétées par une série de caractérisations morphologiques et structurales. Les domaines ferroélectriques à l’origine des propriétés piézoélectriques sont correctement visualisés par PFM et le calcul du coefficient piézoélectrique d33 des couches synthétisées sur des substrats métalliques, est réalisé par interféromètre laser. En parallèle, une approche expérimentale est menée sur l’évolution des performances piézoélectriques des films de PZT d’une part en fonction du mode d’élaboration et d’autre part en fonction de la texturation des couches, assurée par des traitements thermiques de cristallisation. / Recently, PZTs thin films have been spotlighted for various applications owing to their excellent piezoelectric and electromechanical properties. Most of the existing coating methods have been explored for the deposition of PZT. In this work, amorphous Pb(ZrxTi1-x)O3 (PZT) thin films were prepared by pulsed DC and RF magnetron sputtering in order to device a piezoelectric force sensors. The structure of a perovskite phase of PZT thin films was successfully characterized and morphological characterizations were investigated. Ferroelectrics properties of PZT thin films were determined using Piezoresponse Force Atomic technique (PFM) while the functional response of the films was characterized by measurements of piezoelectric d33 coefficients. Additionally, the coating processes and the crystallization behavior at different temperatures, of amorphous PZT thin films during either conventional furnace annealing (CFA) or rapid thermal annealing (RTA) were studied to understand the evolution of piezoelectric properties of films.

Les microsystèmes électromécaniques (MEMS) ont été développés dès le début des années 1980 en s'appuyant sur la technologie de l'industrie microélectronique. Ils ont d'abord été utilisés dans les accéléromètres et les airbags des automobiles. Depuis lors ils se diversifient et connaissent un important essor, notamment grâce à la rapidité De la réponse des matériaux piézoélectriques. La technologie des couches minces piézoélectriques a permis la miniaturisation et les déformations sous tensions d'actionnement plus faibles. Parmi les matériaux piézoélectriques, les films minces de PbZrTiO3 (PZT) morphotropique sont fréquemment utilisés pour leurs propriétés électromécaniques remarquables. Le PZT fabriqué par la voie sol-gel au CEA Leti est à l'état de l'art mondial. Dans le souci de continuer à être compétitif, plusieurs stratégies de R&D sont envisagées, notamment des études approfondies de la microstructure des films PZT pour l'optimiser, afin d'atteindre les propriétés ultimes du PZT. Dans ce but, cette thèse recherche les corrélations entre la microstructure et l'effet piézoélectrique du PZT. Le PZT morphotropique massif, apparu dans les années 1950, est un matériau bien étudié du point de vue microstructurale et piézoélectrique. Il existe plusieurs théories expliquant ses performances piézoélectriques au niveau microscopique. Pour citer les plus connues, le basculement de domaine des phases tétragonale et rhomboédrique, le réarrangement des nano-domaines rhomboédriques, la rotation de l'axe de polarisation dans la phase monoclinique et la transition de phase. Les films minces de PZT morphotropique sont apparus dans les années 1990. Leur microstructure diffère radicalement du PZT massif. Le PZT sol-gel étudié dans ce manuscrit, est contraint et possède une orientation préférentielle des cristaux, des domaines nanométriques et un gradient chimique de Zr et Ti dans l'épaisseur. Notre but est d'étudier les liens entre la microstructure complexe de ces films et leurs propriétés piézoélectriques en utilisant la caractérisation par diffraction des rayons X (DRX). Grace à l'accès au nano-faisceau à l'ESRF, nous avons pu étudier l'influence du gradient chimique de Zr/Ti sur la microstructure de PZT. Les résultats ont montré que la variation de concentration de Zr et Ti engendre une variation du rapport des phases tétragonale et rhomboédrique dans l'épaisseur de la couche. Cette variation suit les oscillations de Zr/Ti dans les films observées par SIMS. Cette observation montre la sensibilité de la microstructure sur la composition chimique. De même, il en résulte la possibilité d'améliorer l'homogénéité de composition du PZT et de ses performances. Car plus le PZT est homogène en composition, meilleurs sont ses coefficients piézoélectriques (d33, e31). Par la suite nous avons effectués des expériences in-situ sous champ électrique sur des capacités contenant le PZT avec le gradient de composition atténué. La microstructure de PZT a été affinée en utilisant la phase tétragonale et rhomboédrique. A 0V, on estime que le PZT contient 40% de phase rhomboédrique et 60% de phase tétragonale. A 30V, on n'observe plus que la présence de la phase rhomboédrique. Les résultats montrent une diminution de la proportion de phase tétragonale au profit de la phase rhomboédrique sous champ électrique. Pour finir nous avons étudié l'influence du gradient de concentration sur l'amplitude du changement de phase en analysant deux échantillons de gradient Zr/Ti différents par DRX in-situ. Nous avons pu montrer que plus l'échantillon est homogène chimiquement, plus il est sujet à la transition de phase sous champ électrique et plus il est performant piézoélectriquement. Finalement, afin d'améliorer les performances piézoélectriques des films PZT, nous proposons de fabriquer des films plus homogènes et plus riches en Ti pour amplifier la transition de phase dans les films. / MEMS have been developed since 1980, when they appeared as derivatives from the microelectronic industry. They were first used in accelerometers and car airbags. They have diversified since then and expanded. One of the main contributors to this expansion are piezoelectric materials. Among them, PbZrTiO3 (PZT) is widely used for its outstanding piezoelectric performances. Sol-gel PZT thin films fabricated at CEA are worldwide state of the art. In order to stay competitive, several R&D strategies have been developed. One of them is a detailed study of PZT microstructure in order to draw correlations with the piezoelectric effect in PZT films. The goal of this study is to optimize PZT microstructure aiming to reach its best piezoelectric properties. For this purpose, this thesis takes advantage of numerous studies performed on PZT bulk ceramics in order to analyze PZT thin films microstructure and its modifications with voltage. PZT bulk ceramics of morphotropic composition are now well known from the piezoelectric and microstructural point of view. There are several theories explaining the piezoelectric effect at the microscopic level, namely tetragonal and rhombohedral domain switching, rhombohedral nanodomains rearrangement, polarization axis rotation in the monoclinic phase and the phase transition.Morphotropic PZT thin films have emerged more recently. Their microstructure is very different from the bulk PZT. Indeed, sol-gel PZT films studied in this manuscript are stressed and contain preferred oriented nanoscale crystals and Ti/Zr composition gradient through the film thickness. Our goal is to study links between the complex microstructure of these films and their piezoelectric properties using X-ray diffraction (XRD).Thanks to the nano-beam at ESRF, we were able to study the influence of the Zr/Ti chemical gradient on the PZT microstructure. Our observations showed that the composition gradient gives rise to a variation of the tetragonal and rhombohedral phase ratio in the layer thickness. This variation follows Zr/Ti composition oscillations evidenced by SIMS. This experiment shows the sensitivity of PZT microstructure to the PZT chemical composition. At the same time, it suggests the possibility of improving the composition homogeneity of PZT and its performances. The more the PZT composition is homogeneous, the better the piezoelectric coefficients are.Then, we performed in-situ XRD under electric field experiments on a capacitor containing the PZT active layer with an attenuated Zr/Ti gradient. The PZT diffraction pattern was refined using the tetragonal and the rhombohedral PZT phases. At 0V PZT contains 40% of rhombohedral phase and 60% of tetragonal phase. At 30V, no tetragonal phase is observed any more. Results show an electric field induced phase transition from the tetragonal to the rhombohedral phase.Finally, we used in-situ XRD to study the influence of Zr/Ti composition gradient on the amplitude of the phase transition of two PZT samples with different Zr/Ti gradient. We showed that the more the sample is homogeneous in composition, the more phase transition it exhibits and the more it is performant.Finally, to improve the piezoelectric performances of PZT films, we propose to improve PZT compositional homogeneity and slightly increase the Ti content to promote the tetragonal phase in order to amplify the phase transition under voltage.

Les actionneurs piézoélectriques se distinguent par leurs faibles temps de réponse et leurs rapports déflexion/ tension d’actionnement élevés. Dans ces travaux, nous nous attacherons à optimiser la déformation de matériaux piézoélectriques. La première approche consiste à augmenter le champ dans la couche active et la seconde à optimiser les coefficients piézoélectriques du matériau. Pour répondre à des problématiques d’actionnement basse tension, des couches de nitrure d’aluminium (AlN) ultraminces ont été déposées et caractérisées. Le coefficient e31,eff s’est avéré être constant entre 800 et 50 nm d’épaisseur, à une valeur de -0,8 C/m², ce qui est proche de l’état de l’art. Le caractère piézoélectrique de l’AlN à une épaisseur de 12 nm a été mis en évidence. Toujours dans l’optique de travailler à champ électrique élevé, une étude visant à augmenter le champ de claquage du titano-zirconate de plomb (PZT) par insertion d’atomes de lanthane a été menée. Le champ de claquage est amélioré de 35% environ, sans que la permittivité diélectrique et les coefficients piézoélectriques ne soit dégradés. La seconde approche consiste à optimiser les coefficients piézoélectriques. Pour cela, le Titano Zircoate de Plomb a été étudié au voisinage de différentes transitions de phases. La transition morphotropique est particulièrement favorable au niveau piézoélectrique, avec un coefficient e31,eff qui atteint -18 C/m² hors champ et -27 C/m² sous champ. La problématique de blocage de parois de domaines a été abordée. La transition de Curie se manifeste principalement au niveau diélectrique, avec une permittivité relative qui atteint 2640 à 370°C, soit près du double de la valeur mesurée à température ambiante. Les pertes diélectriques diminuent entre 25°C et 280°C, pour atteindre 1,6 %. Afin de bénéficier d’une transition critique, du PZT fortement dopé au lanthane a été déposé.Un comportement relaxeur a été mis en évidence et un coefficient piézoélectrique induit d31 de -25 pm/V a été mesuré. Les matériaux développés dans cette thèse ouvrent des perspectives pour la réalisation de microactionneurs et notamment de têtes d’imprimantes jet d’encre. / Piezoelectric actuators exhibit low response times and high deflection/actuation voltage ratios. This PhD thesis aims at optimizing their strain values by increasing the applied field and the piezoelectric coefficients. To target low voltage issues, Aluminum Nitride (AlN) ultrathin layers were deposited and characterized. e31,eff coefficient was found to be constant between 800 and 50 nm, at a value as high as -0.8 C/m². Piezoelectric behaviour was also shown for 12 nm-thick AlN layers, by three different ways. Still in order to apply high electric fields, a study was carried out to improve Lead Zirconate Titanate (PZT) breakdown field, by inserting lanthanum atoms. Breakdown field was improved by approximately 35%, with no decrease of permittivity or piezoelectric coefficients. Another optimization approach consists in increasing the material’s piezoelectric coefficients. In this view, PZT was characterized around several phase transitions. Near morphotropic phase boundary, piezoelectric effect was found to be enhanced: e31,eff coefficient raises up to -18 C/m² at low field conditions and -27 C/m² in actuating conditions. Domain wall pining issue was also discussed. Near Curie transition, dielectric properties were found to be enhanced, with a dielectric constant rising up to 2640 at 370C, which is almost twice as high as room temperature value. Furthermore, dielectric loss decreases from 25C to 280C to reach 1.6%. To profit from a critic phase transition, highly Lanthanum doped PZT was deposited. Relaxor behaviour was shown and an induced piezoelectric coefficient d31 of -25 pm/V was measured. Materials developed in this PhD thesis can be used to realize microactuators and especially inkjet printheads.

MEMS structures utilizing the piezoelectric effect are used to fabricate a wide variation of sensingand actuating devices. The most common piezoelectric material for MEMS is PZT which has beenintensively investigated. In order to improve the performance of PZT and create materialsoptimized for specific applications, altered versions of PZT are being investigated. One way toalter the behavior of PZT is to introduce dopants. In this work, doped and non-doped PZT filmshave been fabricated using the sol-gel deposition process and the transverse piezoelectriccoefficient (e31) value of these films has been measured. Two types of dopants have been used tosee if these dopants could boost the e31 making the film more suitable for energy harvestingapplications. Furthermore processes alteration has been performed to increase the quality andthroughput of the PZT film fabricated at Silex Microsystems. The quality of the film could be seenby inspecting the level of non-uniform areas in regards to color and clarity of the film. The qualitywas improved and the color and clarity uniformity across the wafer was visibly improved. Thethroughput of the PZT deposition process was increased by ~33% by finding an alternative processrequiring fewer crystallization steps. One type of dopant gives an e31 increase of ~12% compared to the highest e31 value previously obtained at Silex Microsystems using non-doped PZT. / Piezoelektrisk MEMS används för att konstruera många olika sorters av sensorer och aktuatorer.Det piezoelektriska material som används mest frekvent inom MEMS är PZT, vilket har blivitintensivt undersökt. För att förbättra prestandan hos PZT och skapa material optimerade förspecifika applikationer, undersöks olika modifikationer av PZT. Ett sätt att modifiera egenskapernahos PZT är att introducera dopningsämnen. I detta arbete har filmer av dopad och odopad PZTtillverkats med en sol-gelprocess och e31-värdet hos dessa filmer har mätts. Två typer avdopningsämnen har använts för att se om ett högre e31-värde kunde nås vilket skulle göra filmenbättre för ”energy harvesting” tillämpningar. Dessutom har process-modifikationer gjorts för attförbättra sol-gel processen hos Silex Microsystems. Modifikationerna gjordes med målet attförbättra kvaliteten hos filmen och minska processtiden. Kvaliteten hos filmen kunde observerasgenom att se i vilken utsträckning filmen var uniform i färg och klarhet. Efter modifikationerna påprocessen så förbättrades både dessa aspekter. Färgskillnader kunde inte längre observeras påfilmen och klarheten ökade. Produktionstiden minskade med ~33% med hjälp av en stabilalternativ process som krävde färre kristalliseringssteg. Ett av dopningsämnena förbättrade e31-värdet med ~12% jämfört med det e31-värdet hos den odopade filmen tidigare skapad av SilexMicrosystems.

The vibration control problem for flexible structures is examined within the context of overall controller performance and power reduction. First, the issue of optimal sensor and actuator placement is considered along with its associated control robustness aspects. Then the option of alternately activating subsets of the available devices is investigated. Such option is considered in order to better address the effects of spatiotemporally varying disturbances acting on a flexible structure while reducing the overall energy consumption. Towards the solution to the problem of optimal device placement, three different approaches are proposed. First, a computationally efficient scheme for the simultaneous placement of multiple devices is presented. The second approach proposes a strategy for the optimal placement of sensors and collocated sensor/actuator pairs, taking into account the influence of the spatial distribution of disturbances. The third approach provides a solution to the actuator location problem by incorporating considerations with respect to preferred spatial regions within the flexible structure. Then the second problem named above is considered. Activating a subset of the available and optimally placed actuators and sensors in a flexible structure provides enhanced performance with reduced energy consumption. Such approach of switching on and off different actuating devices, depending on their local-in-time authority, results in a hybrid system. Therefore the proposed work draws on existing results on hybrid systems and includes an additional degree of freedom, whereby both the actuating devices and the control signals allocated to them are switched in and out. To enable this switching an activation strategy, which insures also that stability-under-switching is guaranteed, is required. Three different strategies are considered for such actuators allocation: first a cost-to-go index is considered, then a cost function based on the mechanical energy of the flexible structure and finally a performance index based on the maximum deviation of the transverse displacement. A flexible aluminum plate was chosen to validate and test the proposed approaches. The set up utilized four pairs of collocated piezoceramic patches that serve to provide sensing and actuating capabilities. Extensive numerical simulations were performed for both the placement strategies and the switching policies proposed, in order to predict the behavior of the flexible plate and provide the optimal actuator and sensor locations that were to be affixed on the flexible structure. Finally, to complete the validation process a sequence of experimental tests were performed. The objective of these tests was to compare the performance of the proposed hybrid control system to traditional non switched control schemes. In order to provide a repeatable perturbation, four of the piezoceramic patches were allocated to simulate a spatiotemporally varying disturbance, while the remaining four patches were used as sensors and controlling actuators. The experimental results showed a significant performance improvement for the switched controller over the traditional controller. Moreover the switched controller exhibited improved robustness towards spatiotemporally varying disturbances while the traditional controller showed a significant loss of controller performance. The improvement achieved in vibration control problems could be extended to a wider range of applications. In particular, although this study was concentrated on a rectangular thin plate, the proposed strategies can be applied to emph{any} structure and more generally to any plant whose dynamics can be represented by a second order linear system. For example, by removing the restriction of spatially fixed actuators and sensors, the proposed theory can be applied to the problem of unmanned vehicles control.