Search

The growth of cracks under the influence of high voltage cyclic electric field in 8/65/35 lanthanum lead zirconate titanate samples was studied. The remanent polarization, coercive field and complex dielectric constant were measured as a function of the number of switching cycles. During the measurement the salt water solution was penetrating through the sample.

Applications of analytical electron microscopy (TEM-EDXS) in investigations of ceramic ferroelectric materials are described and discussed. Emphasis is placed on various PZT and PLZT materials. Mixed oxide and sol-gel derived loose powder, bulk ceramic material and sol-gel derived ferroclectric thin films on various substrates were analyzed and the degree of homogeneity was determined. The influence of TEM sample preparation and the operating conditions of the transmission electron microscope on deterioration of crystal structure, deviation of chemical composition and the formation of a contamination layer are described and discussed.

Pb(Zr0.53Ti0.47)O3(PZT) and PbNi1/3Nb2/3O3-PZT (PNN–PZT) multilayers with Ag/Pd 70/30 inner electrodes have been studied from the point of view of the ceramic–electrode interaction. PZT multilayers have shown silver free ceramic layers, and no lead has been detected in the electrode after sintering. Silver transport through the ceramic is avoided because of low open porosity–close porosity transition temperature. This transition seems to occur prior to the strong increase of the silver vapour pressure. For PNN–PZT multilayers, similar behaviour to that commonly reported in the literature for PZT is observed. A constant amount of silver, independent of the distance from the electrode, is detected in the ceramic layer. Lead is also detected in the electrode. On the other hand, no interaction between ceramic and electrode has been observed for the other cations.

The electro-optic (EO) properties of a new lead-free ceramic based on a (1−x)K0.5Na0.5NbO3–xSrTiO3 solid solution with x = 0.2 have been investigated. This material has a pseudo-cubic perovskite structure and typical relaxor-like properties for x ~0.15–0.25 (see Kosec M et al 2004 J. Mater. Res. 19 1849–54 and Bobnar V et al 2004 Appl. Phys. Lett. 85 994–6).Measurements of the electric field induced changes in birefringence at room temperature showed a rather large quadratic EO Kerr effect (n3Reff ~1.9 × 10−16 m2 V−2), with strong dispersion (decrease) in the kilohertz region. Electric field induced second harmonic generation was also observed.

AbstractThis study revealed the influence of crystallisation processes on the homogeneity of the sol–gel PbZr0·52Ti0·48O3 thin films, allowing identification and further optimisation of thin film performance. Crystallisation processes determine the optical gradient appearance, irrespective of the chemical solvents used in this work. X-ray diffraction analysis showed that a refractive index gradient was apparent in the samples which had dominant (001)/(100) orientation and significant change of lattice parameters with thickness.

Temperature-dependent stress-strain behavior of various soft Pb${}_{0.98}$Ba${}_{0.01}$(Zr${}_{1\ensuremath{-}x}$Ti${}_{x}$)${}_{0.98}$Nb${}_{0.02}$O${}_{3}$, $0.40\ensuremath{\le}x\ensuremath{\le}0.60$, compositions was characterized between 25 and 400 \ifmmode^\circ\else\textdegree\fi{}C to determine the influence of crystal structure on ferroelasticity. The ferroelastic response was found to depend significantly on the crystal phase as well as the spontaneous strain, both of which varied with temperature. The remanent strain for rhombohedral materials was shown to be above the theoretical maximum allowed by the crystal spontaneous strain. This observed behavior indicates the presence of hysteretic processes in addition to ferroelasticity during mechanical compression. A phenomenological free energy analysis was used to predict the effects of stress on the stable phase in ferroelectrics and indicates the susceptibility of the rhombohedral and tetragonal structure to a stress-induced phase transition. Modeling results indicate the relative importance of such phase transitions on macroscopic stress-strain behavior, giving an indirect method to observe field-induced phase transitions in polycrystalline ferroelectrics.

Solution processing of functional oxides often starts with rather complex precursor systems consisting of metal alkoxides, carboxylates and/or nitrates dissolved, mixed and reacted (modified) in different solvents. Precursor systems of main functional perovskite groups are reviewed in this chapter. The breakthrough was achieved in mid-1980s, when the 2-methoxyethanol route was developed for processing of Pb(Zr,Ti)O3-based films, in which this ether alcohol is used as the solvent, acetates as the A-site and alkoxides as the B-site ion sources. Two other very popular routes are the diol-route, in which 1,3-propanediol is used as the solvent, and the so-called inverse-mixing-order route, in which the B-site cations are mixed first and the A-site source is added afterwards. In the alkali metals-based systems, such as Li(Nb,Ta)O3, (K,Na)(Nb,Ta)O3, and Na0.5Bi0.5TiO3, several methods have been developed in which different starting metallo-organic compounds have been used as the A-site metal sources, while mainly alkoxides have been employed as the B-site precursors. A variety of solvents can be used, such as methanol, ethanol, 2-methoxyethanol, 1,3-propanediol, as well as modifiers, for instance acetic acid, acetylacetone, and polyvinylpyrrolidone. Even water has been employed in some systems. The chapter concludes with the review of (Ba,Sr)TiO3-based precursor systems, mainly involving A-site carboxylates and stabilized Ti-alkoxides mixed in one of the above mentioned solvents.

Introduction.-Solution Chemistry Simple alkoxide based precursor systems Carboxylate based precursor systems Single-source precursors Acqueos Precursor Systems Solution Synthesis Strategies.-Analytical Methods Introduction Thermal Analysis NMR Sepctroscopy EXAFS Other Methods (XRM, SEM,TEM scattering methods at nanocrystalline films) Spin-Coating Dip Coating Inkjet Printing and Other Direct Writing Methods(dip point and imprint techniques) Chemical Bath Deposition Polymer Assisted Deposition.-Processing and Crystallization Thermodynamics and Heating Processes Material Systems Dominated by Heterogeneous Nucleation Material Systems Dominated by Homogeneous Nucleation Low Temperature Processing Epitaxial Films Powder Assisted Film Fabrication UV-and E-Beam Direct Patterning of Photosensitive CSD Films Template Controlled Growth.-Functions and Applications Introduction Integrated Capacitors Base Metal Electrodes Polar Oxide Films for MEMS Applications Conducting Films and Electrodes Transparent conducting oxides Superconducting Films Porous Films for Gas Sensors Luminescent Fims.-Appendix Synthesis for Standard material Systems.

Aliovalent Nb doping (less than or equal to 10 at.%) of sol-gel-derived lead zirconate titanate (PZT) thin films was investigated with the intention of improving the ferroelectric properties. Nb addition was found to significantly alter the perovskite crystallization by stabilizing the transient pyrochlore phase, resulting in the retention of pyrochlore second phases and an increase in the perovskite lateral grain size and columnarity. The occurrence and composition of Zr-rich (surface) pyrochlore phases were found to depend on Nb concentration, annealing temperature, and Pb content. The observed changes in ferroelectric and dielectric properties as a function of Nb dopant addition were found to be strongly influenced by microstructural effects and the occurrence of pyrochlore, and hence the intrinsic effects of Nb incorporation in the perovskite lattice could not be directly ascertained.

Ferroelectric ceramic materials based on solid solutions of Pb(Zr,Ti)O3 (PZT) are used in the electronics industry for sensors and actuators and for electromechanical transducers, to name just a few examples. Thick-film technology, i.e., the deposition of thick-film pastes by screen printing, primarily on alumina substrates, is a relatively simple and convenient method to produce layers with a thickness up to 100 μm. The characteristics of thick-film ferroelectrics are similar to those of bulk materials [1–4]. Low-temperature co-fired ceramics (LTCC) materials, which are sintered at the low temperatures typically used for thick-film processing, i.e., around 850 ◦C, are based either on crystallizable glass [5, 6] or a mixture of glass and ceramics, for example, alumina, silica or cordierite (Mg2Al4Si5O18) [7, 8]. Jones et al. have presented a comparison of the mechanical and chemical characteristics of both green and fired LTCC tapes from different suppliers in [9]. Ceramic multi-chip modules (MCM-C) are multilayer substrates with buried conductor lines. An additional contribution to the smaller size and the higher density of MCM-C is the ability to integrate screenprinted resistors, or sometimes capacitors and inductors. These screen-printed components can be placed either beneath the discrete components on the surface of the multilayer dielectric or buried within the multilayer structure. For an overview of passive integrated components in MCM see, for example [10]. For some applications, for example integrated sensors or micro-actuators, PZT thick-films on LTCC that are sintered at relatively low temperatures (around 850 ◦C) comparable with LTCC’s firing temperatures, would be of interest [11, 12]. The aim of this work was to study the compatibility between LTCC and screenprinted PZT as well as the electrical characteristics of the PZT layer. PZT 53/47 powder (PbZr0.53Ti0.47O3) with an excess 6 mol% of PbO was prepared by mixed-oxide synthesis at 900 ◦C for 1 h from high-purity PbO (litharge) 99.9% (Fluka), ZrO2 99% (Tosoh), and TiO2 99% (Fluka). To this was added 2 wt% of lead germanate, with the composition Pb5Ge3O11 (melting point 738 ◦C) as a sintering aid. Lead germanate (PGO) was also prepared by mixed-oxide synthesis from PbO and GeO2 99% (Ventron) at 700 ◦C. After synthesis, both compositions were ball milled in acetone for 1 h and dried. A thick-film paste was prepared from the PZT (2% PGO) and an organic vehicle (ethyl cellulose, alpha-terpineol and butil carbitol acetate) by mixing on a three roll mill. The green LTCC 951 tape (Du Pont) and alumina ceramics were used for substrates. The thick-film structure was prepared by first printing gold film (Remex 3243) and then the PZT film. The PZT film was printed 6 times with intermediate drying. The gold and PZT layers were cofired at 850 ◦C for 8 h in a closed alumina crucible. The thickness of the PZT films after the thermal treatment was around 50 μm. The green and fired Du Pont LTCC 951 tapes were analyzed by X-ray diffraction (XRD) analysis with a Philips PW 1710 X-ray diffractometer using Cu Kα radiation. X-ray spectra were measured from 2 = 20 ◦ to 2 = 70 ◦ in steps of 0.04 ◦. X-ray spectra are shown in Fig. 1. The unfired material is a mixture of alumina and glass. After firing at 850 ◦C peaks of anorthite ((Na,Ca)(Al,Si)4O8) phase appear. The peaks of alumina and anorthite are denoted by “A” and asterisk, respectively. For the electrical measurements gold electrodes were sputtered onto the PZT films. The values of the remanent polarization and the coercive field were determined from ferroelectric hysteresis curves measured with an Aixact TF Analyzer 2000 at 50 Hz. The real and imaginary parts of the complex dielectric constant were measured with an HP 4284 A Precision LCR Meter at 1 kHz. In Table I the electrical parameters, i.e., remanent polarization Pr, coercive field Ec, dielectric constant e′ and dielectric loss tan δ, of the co-fired LTCC/Au/PZT structure are presented. The electrical characteristics of this structure are compared to the characteristics of a similar structure printed on alumina substrates [13]. Hysteresis loops of the PZT films on the alumina and LTCC substrates are shown in Fig. 2.

Piezoelectric lead zirconate titanate (PZT) thick films were prepared on flat and curved substrates by electrophoretic deposition (EPD) process. PZT and PbO particles were dispersed in ethanol to obtain a stable suspension and deposited on flat alumina at constant current density of 1.56 mA/cm2 for 90 seconds and on curved unpoled porous PZT substrates at constant current density of 3.57 mA/cm2 for 60 seconds. The deposits were sintered at 950°C for 2 hours in a PbO-controlled atmosphere. The thickness of the PZT film on curved substrate is 30 μm and the porosity is 17 %. An effective thickness coupling factor of around 50 % and a dielectric constant at constant strain of 320 were measured on flat substrate. An operating high frequency single element transducer with a center frequency close to 30 MHz was fabricated and characterized. The transducer was integrated into an echographic imaging system. In-vivo skin images were illustrated to show the great potential of EPD method for the fabrication of high frequency transducers for medical applications.

By utilizing direct measurements of the electrocaloric effect (ECE) temperature change via high-resolution calorimeter, the ECE has been studied in bulk lead-free relaxor K 0.5 Na 0.5 NbO 3 -SrTiO 3 (KNN-STO) ceramics. Observed magnitude of the ECE confirms existence of the large EC effect in this system near the ferroelectric phase transition.

Since the first laboratory experiments of M. Carey Lea and the original definition by F. W. Ostwald at the end of the 19th century, mechanochemistry, a field treating chemical changes induced in substances as a result of applied mechanical stress, has been evolved as an important area of chemistry from the viewpoint of both the fundamental research and applications (Takacs, 2004; Boldyrev & Tkacova, 2000). Whereas the fundamentals of mechanochemistry are still being extensively explored, the mechanical alloying, a powder metallurgy process involving ball milling of particles under high-energy impact conditions, met the commercial ground as early as in 1966 and was used to produce improved nickeland iron-based alloys for aerospace industry (Suryanarayana et al., 2001). In addition to metallurgy, the science and technology of mechanochemical processes are continuously developing within various other fields, including ceramics processing, processing of minerals, catalysis, pharmaceutics, and many others.

The chapter attempts to describe the potential of sol-gel derived ferroelectric thin films in energy conversion applications in two fields, namely in cooling by exploiting the electrocaloric effect and in energy harvesting. First, the basics of the sol-gel processing of ferroelectric thin films with the Pb(Zr,Ti)O3 solid solution as the representative material are described. The electrocaloric effect is described as a reversible temperature change in a material under an applied electric field at adiabatic conditions. Sol-gel derived relaxor ferroelectric thin films demonstrate a giant electrocaloric effect and they could be applied for solid-state cooling devices in microelectronics. In energy harvesting, the energy is derived from external sources, captured, stored and used, for example in small autonomous devices. In ferroelectric thin films, the piezoelectric effect, i.e. the generation of an electric charge upon applied stress, is exploited. Due to the miniaturization of electronic components, thin films with lateral dimensions in nanometer to micrometer range are appropriate candidates for future miniature applications related to energy.

International audience; Lead–zirconate–titanate (PZT) thick films for high‐frequency ultrasound applications were fabricated using an electrophoretic deposition (EPD) process. The PZT powder was synthesized from constituent oxides at close‐to‐room temperature by mechanochemical activation followed by calcination at 700°C. Homogeneous PZT thick films with a thickness of ~30 μm and a density of ~80% were produced from ethanol‐based colloidal suspensions containing PZT and PbO particles that were deposited using a constant‐current mode on a platinized alumina substrate and were sintered in the presence of a liquid phase at temperatures compatible with thick‐film technology. The dielectric, mechanical, and piezoelectric parameters of the PZT thick films with a porosity of ~20% were measured and a thickness‐coupling factor of 48% was obtained. Considering that a PZT thick film is a composite structure consisting of PZT and pores, there are several methods that can be applied to calculate the effective parameters where the composite is considered as a piezoelectric homogeneous material. For this study, a matrix method based on a generalization of 2‐2 connectivity was used to deduce the parameters of a completely dense configuration. Our results confirmed that the EPD process is suitable for the fabrication of efficient, high‐frequency transducers operating at frequencies above 40 MHz.

In this investigation we show that the dielectric, ferroelectric and piezoelectric properties of stoichiometric 0.57Pb(Sc 1/2 Nb 1/2 )O 3 –0.43PbTiO 3 (0.57PSN–0.43PT) ceramics prepared by mechanochemical synthesis are comparable or even better than the properties of 0.57PSN–0.43PT ceramics with Nb doping, which was proposed to enhance the electrical properties. Here, the stoichiometric ceramic was sintered to 97% of theoretical density at a temperature of 1000 °C, which is 200–300 °C lower than previously reported. The dielectric constant ɛ , remnant polarization P r , piezoelectric coefficient d 33 , coupling coefficients k p and k t and mechanical quality factor Q m of the ceramics prepared by mechanochemical synthesis were 2200, 43 μC/cm 2 , 570 pC/N, 0.71, 0.56 and 38, respectively. The effects of the poling field on the structural and electrical properties of the 0.57PSN–0.43PT ceramics were investigated. The results show that the ratio of the monoclinic to the tetragonal phases is influenced by the application of the poling electric field. The non-poled ceramics contain 71% of the monoclinic phase and 29% of the tetragonal phase. The highest d 33 , k p and k t were measured for ceramics poled at an electric field of 3 kV/mm. For these poled ceramics a phase determination of 86% monoclinic phase and 14% tetragonal phase was obtained from Rietveld refinements.

We report the processing of NaNbO3 nanopowder by combining the solid-state synthesis and subsequent milling in the agitator bead mill. The effect of different rotation speeds of the agitator shaft on the comminution process was followed by laser granulometry. The morphology and specific surface area of the powders were investigated by scanning electron microscopy and the N2 adsorption method, respectively. With the optimized milling parameters, we obtained NaNbO3 nanoparticles with an average size of 25 nm and a narrow particle size distribution. The result is comparable to other processing techniques, such as solution-based chemical routes or mechanochemical synthesis; however, the presented method does not require any complicated processing and it can be easily upscaled to yield large quantities of the NaNbO3 nanopowder. Furthermore, the compaction behaviour of the obtained nanopowder was investigated, and a compaction-response diagram was constructed revealing good compactability of the powder. The green compacts, isostatically pressed at 740 MPa, had a relative density of 70% and a narrow pore size distribution with an average pore radius of 4 nm.

Sb doped and undoped SnO2 thin solid coatings were prepared by the dip-coating technique via the sol-gel route. Aqueous gels of undoped compound were made by using a SnCl4 precursor and doping was achieved through the addition of SbCl3 in the concentration range 1–10 mol%. Fourier transform infrared (FTIR), ATR and near normal reflectance spectroscopic techniques were utilized to determine the vibrational spectra of aqueous gels, xerogels and oxides of Sb doped and undoped compounds. Analysis of the corresponding FTIR spectra revealed the existence of Sb-O modes at 770 cm−1. The drying of both types of gel was accompanied by the formation of hydrogen bonds of medium strength wit the OH-O length about 2.7–2.8 A. Some properties of pure and Sb doped oxide powders formed in the temperature range ≤1000°C were measured by the thermogravimetry, X-ray diffraction and FTIR spectroscopic techniques. The doping brought about a broadening of the X-ray diffraction peaks. The reflectivity of the samples increased in the spectral range 4000-600 cm−1 up to 60%, due to the formation of plasma modes. Thin solids films were made by the dip-coating method. The efficiency of the dip-coating process was 0.02–0.1 μm per dipping, depending on the viscosity of the gel. The electrical resistivity of the doped SnO2 coatings was about 1.2 × 10−2 ω cm and thus comparable to the electrical resistivity of the alkoxide derived Sb doped SnO2. Doping decreased visible transmittance ∼5% but infrared reflectance increased up to 40%, depending on the film thickness.

Due to the toxic nature of PbO in Pb(Zr,Ti)O3 (PZT), the most common type of piezoceramic, many studies on lead-free materials are being conducted worldwide (Roedel et al., 2009). One of the most studied groups of lead-free ferroelectric materials is based on a solid solution of potassium sodium niobate, K0.5Na0.5NbO3 (KNN) (Jaffe et al., 1971; Kosec et al., 2008). However, activity in attempts to find a lead-free replacement for PZT really accelerated with the discovery of textured (K,Na,Li)(Nb,Ta,Sb)O3 ceramics, with properties comparable to those of PZT (d33> 300 pC/N, relative permittivity > 1500, planar coupling coefficient kp> 60%)(Saito et al., 2004). One way to enhance the piezoelectric properties of KNN is to grow KNN-based single crystals along certain crystallographic directions, as has been demonstrated for the case of KNbO3 (Wada et al., 2004) and relaxor-based ferroelectric single crystals (Park & Shrout, 1997). The most frequently used methods for growing alkali niobate based single crystals are top seeded solution growth and the flux methods (Chen et al. , 2007; Davis et al., 2007; Kizaki et al., 2007; Lin et al., 2009). However, these methods are not yet fully commercialized due to high costs and poor reproducibility related to compositional inhomogeneity within the crystals. A possible way to improve the homogeneity of crystals with complex composition is to grow them by the low cost Solid State Single Crystal Growth (SSCG) method. The SSCG method is essentially a form of induced abnormal grain growth, a phenomenon which is very well known in the solid state sintering community. A significant breakthrough in the solid state synthesis of lead-free materials has been achieved in recent years (Kosec at al., 2010; Malic et al., 2008a). However, due to the strongly hygroscopic nature of alkaline carbonates usually used in solid state synthesis, different diffusion rates of involved ionic species during annealing, and the high sublimation rates of the alkaline species at high temperatures (Bomlai et al., 2007; Jenko et al., 2005; Kosec & Kolar, 1975; Malic et al., 2008b), it may be rather difficult to obtain compositionally homogeneous alkali niobate-based single crystals by SSCG.

Electroceramic thick films are 2D (planar) structures that, in their simplest form, consist of a substrate, a bottom electrode, a ceramic film and a top electrode, with the thickness of an individual layer being typically between 1 and 100 μm. The processing of thick films is similar to the processing of bulk ceramics, i.e., it involves powder synthesis, shaping and sintering. The major difference, however, is in the clamping of the film onto the substrate. The consequences of this are a constrained sintering, a possible reaction with the electrode or the substrate during firing, and the thermal stresses that are generated during the cooling. To minimize the chemical interaction of the film and the substrate the sintering temperature must be kept relatively low in comparison to that for the bulk. This requires a fine particle size for the powder and additives that form a liquid phase at the sintering temperature. This liquid phase must also be present to enable the densification under the constrained conditions, as was predicted and demonstrated in Kosec et al. (1999). The effect of clamping the active film to the relatively stiff substrate results in smaller displacements in comparison to substrate-free structures. Due to the mismatch of the thermal expansion of the thick-film and substrate materials during the processing the properties of the thick films differ from those of the respective bulk ceramics. Furthermore, an additional drawback can be the deterioration of the thick film’s properties due to its chemical interaction with the substrate. To ensure a sufficient displacement required for a certain application, different solutions have been proposed, such as a reduction in the thickness of the substrate, the processing of thick-film multilayer structures or the preparation of “substrate-free” structures. In the world of technology there is a continuous, global increase of interest in the miniaturisation of devices, materials and system integration. Thick-film structures are a good example of the opportunities offered for the miniaturization of electromechanical systems by the successful implementation of new functional materials and technologies. Driven by the versatility of conventional thick-film technology, the processing of functional structures with thick films on different substrates is possible, along with many design possibilities. In this chapter the progress in relaxor-ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) thick films is reported. The preparation procedures, the processing of PMN–PT thick films on different substrates, the structural and electrical characterization as well as PMN–PT thick-film devices are discussed. The phase composition and functional properties of PMN– PT thick films are discussed in terms of the thermal stresses generated in the films during

Dielectric materials, which are used to control and store charges and electric energy, play a key role in modern electronics and electric power systems. As commercial and consumer requirements for compact and low cost electronic and electrical power systems as well as for very high energy capacitive storage systems grow substantially, the development of high dielectric constant materials has become one of the major scientific and technology issues (Reynolds & Buchanan, 2004; Scott, 2007). High dielectric constant materials are highly desirable for use, not only as capacitor dielectrics, but also in a broad range of advanced electromechanical applications, such as actuators, sonars, and, particularly, as highfrequency transducers (Zhang et al., 2002). The input electric energy that can be converted into the strain energy is namely directly proportional to the square of the electric field and to the dielectric constant of the electroactive material. Thus, by increasing the dielectric constant the required electromechanical response, i.e., strain can be induced under a much reduced electric field. Extremely large dielectric constants are expected only for ferroelectrics in a very narrow temperature range close to the paraelectric-to-ferroelectric phase transition or for systems with hopping charge carriers yielding dielectric constant that diverges towards low frequencies. High-capacitance ceramic capacitors are therefore mostly made of very thin layers of ceramic material (usually a ferroelectric) placed between conductive plates. The most important part of the market in passive devices is, at present, made up of multilayer ceramic capacitors (MLCCs), comprising alternating thin layers of conductor (inner electrodes) and ceramic (Takeshima et al., 1997), which turns out to be the most efficient geometry for attaining high-density charge storage. A similar geometrical approach can also intuitively explain the dielectric response of a percolative composite − a composite comprising a conductive filler embedded in a dielectric matrix. The fact that the effective dielectric constant of the mixture is much larger than the dielectric constants of the individual constituents is due to the fact that close to the percolation point (the volume fraction when the conductive admixture forms a continuous network and, consequently, the system begins to conduct electricity) there are many conducting particles which are isolated by very thin dielectric/ferroelectric layers. A comparison between configurations of a MLCC and a percolative composite is presented in Fig. 1. Unfortunately, the percolative

International audience; Relaxor ferroelectrics are a prototypical example of ferroic systems in which interplay between atomic disorder and order parameters gives rise to emergence of unusual properties, including non-exponential relaxations, memory effects, polarization rotations, and broad spectrum of bias- and emperatureinduced phase transitions. Despite more than 40 years of extensive research following the original discovery of ferroelectric relaxors by the Smolensky group, the most basic aspect of these materials - the existence and nature of order parameter - has not been understood thoroughly. Using extensive imaging and spectroscopic studies by variable-temperature and time resolved piezoresponse force microscopy, we fi nd that the observed mesoscopic behavior is consistent with the presence of two effective order parameters describing dynamic and static parts of polarization, respectively. The static component gives rise to rich spatially ordered systems on the 100 nm length scales, and are only weakly responsive to electric fi eld. The surface of relaxors undergoes a mesoscopic symmetry breaking leading to the freezing of polarization fl uctuations and shift of corresponding transition temperature.

Il report presenta lo stato di avanzamento del work package WP5: "Development of tailored metal oxide films" del partner Jozef Stefan Institute nell'ambito del Progetto Europeo "ORAMA".

Combining the ferroelectric and magnetic components into the solid solution it is expected to obtain the magneto-electric multiferroic material. Novel bulk ceramic compounds xPZT+(1-x)PFW (PZT=Pb(Zr_{; ; 0.53}; ; Ti_{; ; 0.47}; ; )O_{; ; 3}; ; , PFW=Pb(Fe_{; ; 2/3}; ; W_{; ; 1/3}; ; )O_{; ; 3}; ; ) for x=0.15, 0.20, 0.25, 0.50, 0.70, 0.80 were synthesized and their magnetic investigation was performed, including the measurement of zero-field cooled (ZFC) and field-cooled (FC) magnetization curves, magnetic hysteresis loops and a.c. susceptibility. In the low temperature region (below 20K) the splitting between ZFC and FC curves together with the peaks in a.c. susceptibility course point to the blocking/freezing of magnetic moments and magnetic relaxor-like behaviour. The glassy freezing approach to the shift of the susceptibility peaks with frequency gives the activation energies that exhibit a maximum around x=0.5. This is in agreement with the behaviour of blocking/freezing temperatures.

Il report presenta lo stato di avanzamento del work package WP2: "Synthesis of precursors and target materials" del partner Jozef Stefan Institute nell'ambito del Progetto Europeo "ORAMA".

The rapid development of the electronics industry has created the need for highperformance, high-reliability, miniaturised electronic components integrated into various electronic devices. Additional requirements, such as the desired size and weight, low cost, low power consumption, and portability, should be considered to make the devices user friendly and widely accessible. Attempts to miniaturise discrete elements have generally failed due to the difficulty in handling and assembly. A lot of waste material and high costs are also involved. In this approach, the ceramic parts are manufactured as a bulk ceramic, followed by a reduction in size by cutting, polishing, etc., to specified dimensions. The final step is the assembling of a thin layer of ceramic with the other components. This topdown approach imposes limits on the minimum dimensions of the manufactured parts. It constrains the geometry of the parts to simple shapes, like discs, plates, rings, cylinders, etc.

The dilatation-temperature curves of the PZT-ZrO2 composites, containing 1.3–13.2 vol% ZrO2 were studied. The course of martensitic transformation (MT) of dispersed ZrO2 particles in the PZT matrix was followed. Upon cooling, a spontaneous microcrack formation occurred during the MT from tetragonal to monoclinic crystal phase of ZrO2. The phenomenon of intensive shrinkage above 800 °C upon heating is explained as a process of microcrack healing in the presence of the PbO-rich liquid phase.

The joint meeting of 12th International Meeting on Ferroelectricity and 18th IEEE International Symposium on Applications of Ferroelectrics (IMF-ISAF-2009) was hosted by the Electronic Materials Research Laboratory (EMRL) of Xi'an Jiaotong University from August 23 to 27, 2009 at Xi'an, China.

The influence of the processing conditions on the structural properties of a selected LTCC material (Du Pont 951) was studied. The samples were fired at different temperatures; after which, the unfired and fired tapes were characterized by X-ray powder diffraction analysis (XRD) and scanning electron microscopy (SEM). The XRD patterns were then refined using the Rietveld method, with an internal standard being used to quantify the ratio between the crystalline and amorphous components. The results show that this LTCC tape is composed of alumina, as a ceramic filler, and crystallizing glass. By increasing the firing temperature the alumina is dissolving in the melted glass phase. The mass fraction of the crystallization product, the anorthite, increased with the firing temperature. The mass fraction of the glass phase firstly increased with the increasing firing temperature due to the dissolution of alumina, but after the start of the crystallization of the anorthite from the glass phase the mass fraction of the glass decreased with a further increase in the firing temperature. The XRD results are supported by microstructural analyses.

Aliovalent Nb doping (less than or equal to 10 at.%) of sol-gel-derived lead zirconate titanate (PZT) thin films was investigated with the intention of improving the ferroelectric properties. Nb addition was found to significantly alter the perovskite crystallization by stabilizing the transient pyrochlore phase, resulting in the retention of pyrochlore second phases and an increase in the perovskite lateral grain size and columnarity. The occurrence and composition of Zr-rich (surface) pyrochlore phases were found to depend on Nb concentration, annealing temperature, and Pb content. The observed changes in ferroelectric and dielectric properties as a function of Nb dopant addition were found to be strongly influenced by microstructural effects and the occurrence of pyrochlore, and hence the intrinsic effects of Nb incorporation in the perovskite lattice could not be directly ascertained.

Piezoelectric thick films based on Pb(Zr, Ti)O 3 (PZT) were prepared on LTCC substrates and on relatively inert alumina substrates. The results obtained with the alumina were used as a reference. The microstructures of the cross-sections of the PZT layers were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) analysis. The dielectric permittivities, dielectric losses, remanent polarisations, coercitive fields and piezoelectric constants d 33 were measured. The dielectric and piezo electric characteristics of the PZT fired on the LTCC substrate deteriorated, as compared with samples on alumina, due to interactions between the LTCC substratse and the PZT layers. This was attributed to the diffusion of the glassy phasee from the LTCC into the active PZT layer and to the diffusion of the PbO from PZT layer into the LTCC substrates.

Using mechanochemical activation, a homogeneous (K0.485Na0.485Li0.03)(Nb0.8Ta0.2)O3 (KNLNT) solid solution can be obtained after subsequent calcination and sintering. The present study aims to elucidate the origin of the high homogeneity of the activated powder and its relation to the synthesis of KNLNT ceramics. To investigate the effect of the milling conditions, the high-energy milling experiments were performed under different regimes, distinguished by the extent of the impact and frictional force components acting on the powder particles. In addition to this, each one of the starting compounds were also activated separately and then mixed together so as to avoid mechanochemical interactions. This enables us to verify whether the reaction between the constituents during high-energy milling has an effect on the synthesis of KNLNT. The results show that during the activation of the mixture, the symmetry of the CO32− ions, present initially in K2CO3 and Na2CO3, is lowered. This is induced mechanochemically by the reaction with Nb2O5 and Ta2O5. As a result, an amorphous carbonato complex is formed, which plays a crucial role in obtaining highly homogeneous KNLNT ceramics.

Piezoelectric PZT ceramics with the addition of 1.3–13.2 vol% ZrO2 were prepared. It was found that the addition of up to 8 vol% ZrO2 leads to higher values of flexural strength as compared to pure PZT, whereas the electric properties of the composites decrease with ZrO2 addition. Both phenomena are explained on the basis of the effect of martensitic transformation of dispersed ZrO2 particles in PZT matrix. Subsequent thermal treatment of the composites leads to lower values of flexural strength and increased electric properties relative to the as fired samples.

We present electric and magnetic properties of 0.8Pb(Fe1/2Nb1/2)O3-0.2Pb(Mg1/2W1/2)O3 films epitaxially grown on (001) SrTiO3 substrates using pulsed laser deposition. A narrow deposition window around 710 oC and 0.2 mbar has been identified to achieve epitaxial single-phase thin films. A typical Vogel-Fulcher relaxor-like dielectric and magnetic susceptibility dispersion is observed, suggesting magnetoelectric relaxor behavior in these films similar to the bulk. We determine a magnetic cluster freezing temperature of 36 K, while observing weak ferromagnetism via magnetic hysteresis loops up to 300 K., 12 pages, 4 figures

The goal of this work is to compare the functional properties of piezoelectric PZT thick films fabricated by electrophoretic deposition process with those of films obtained by screen printing technique. Thick film fabrication, structural and electromechanical characterizations are reported. The density of the film is 82 % of the theoretical density and coupling coefficient is 47 %. The simulations of the electroacoustic performance of a 40MHz integrated ultrasonic transducer shows that such fabrication process lead to transducer performance suitable for high resolution medical imaging.

This paper presents the crystal structure and the phase transitions of K x Na 1− x NbO 3 (0.4 ≤ x ≤ 0.6). X-ray diffraction measurements were used to follow the change of the unit-cell parameters and the symmetry in the temperature range 100–800 K. At room temperature all the compositions exhibited a monoclinic metric of the unit cell with a small monoclinic distortion (90.32° ≤ β ≤ 90.34°). No major change of symmetry was evidenced in the investigated compositional range, which should be characteristic of the morphotropic phase-boundary region. With increasing temperature, the samples underwent first-order monoclinic–tetragonal and tetragonal–cubic transitions. Only the potassium-rich phases were rhombohedral at 100 K.

This paper deals with the transmission of acoustic waves through multilayered piezoelectric materials. It is modeled in an octet formalism via the hybrid matrix of the structure. The theoretical evolution with the angle and frequency of the transmission coefficients of ultrasonic plane waves propagating through a partially depoled PZT plate is compared to finite element calculations showing that both methods are in very good agreement. The model is then used to study a periodic stack of 0.65 PMN-0.35 PT/0.90 PMN-0.10 PT layers. The transmission spectra are interpreted in terms of a dispersive behavior of the critical angles of longitudinal and transverse waves, and band gap structures are analysed. Transmission measurements confirm the theoretical calculations and deliver an experimental validation of the model.

We have grown lead iron niobate thin films with composition Pb(Fe1/2Nb1/2)O3 (PFN) on (0 0 1) SrTiO3 substrates by pulsed laser deposition. The influence of the deposition conditions on the phase purity was studied. Due to similar thermodynamic stability spaces, a pyrochlore phase often coexists with the PFN perovskite phase. By optimizing the kinetic parameters, we succeeded in identifying a deposition window which resulted in epitaxial perovskite-phase PFN thin films with no identifiable trace of impurity phases appearing in the X-ray diffractograms. PFN films having thicknesses between 20 and 200 nm were smooth and epitaxially oriented with the substrate and as demonstrated by RHEED streaks which were aligned with the substrate axes. X-ray diffraction showed that the films were completely c-axis oriented and of excellent crystalline quality with low mosaicity (X-ray rocking curve FWHM, 13 Pages, 6 figures. To be published in J. Mag. Mag Mater. proceedings of EMRS2008

The correlation between the ferroelectric fatigue and variations in piezoelectric properties in a 8/65/35 (Pb, La) (Zr, Ti)O3 thick film was studied by simultaneous measurements of the polarization hysteresis loop, the strain-field loop, the piezoelectric constant, and the dielectric constant during cycling. It was found that the fatigue reflects itself in the variations of the piezoelectric constant and the induced strain. Namely, during cycling both quantities decrease for the same relative amount as the remanent polarization. In addition, the effective electrostriction constant as a function of switching cycles was determined.

The contribution concerns various processing issues of ferroelectric thin films made by chemical solution deposition. The first part is related to PZT thin films prepared by 2-methoxy-etanol route on Silicon substrate. A careful molecular design of Pb(Zr,Ti)O3 (PZT) precursor solution enables to lower processing temperature of titanium rich films (PZT 30/70) down to 400oC and the composition close to morphotropic phase boundary (PZT 50/50) to 500oC The dielectric properties of the films are well compared to those crystallized at 650?700oC. Clear correlation between enhanced dielectric properties and improved chemical homogeneity provided by precursor structure is demonstrated. The dielectric permittivity 1500 of PZT 50/50 makes these films attractive for capacitor application. The second part relates the processing issues and dielectric properties of (Ba,Sr)TiO3 (BST 30/70) thin films. Films are processed by 2-methoxy-etanol route using acetates and alkoxide precursors. They are deposited on alumina substrates. High frequency dielectric properties depend substantially on processing conditions. Dielectric permittivity and tunability increase with the increase of processing temperature due to increased grain size and better crystallinity. The properties also depend on heating regime. Two step annealing is introduced, where the first thin layer of the same composition serves as nucleation layer for the following deposition. Similar procedure is used for K(Ta, Nb)O3 (KTN 60/40) films. The films exhibit high dielectric constant and high tunability. The application of BST film in phase shifting device is demonstrated.

In this work, the results of compositional and microstructural analysis of lead zirconate titanate--lanthanum ruthenate thin film structures prepared by chemical solution deposition are discussed. The cross-section transmission electron microscope (TEM) micrographs of the La-Ru-O film deposited on a SiO2/Si substrate and annealed at 700 degrees C revealed RuO2 crystals embedded in a glassy silicate matrix. When the La-Ru-O film was deposited on a Pt/TiO2/SiO2/Si substrate, RuO2 and La4Ru6O19 crystallized after annealing at 700 degrees C. After firing at 550 degrees C randomly oriented lead zirconate titanate (PZT) thin films crystallized on the La-Ru-O/SiO2/Si substrate, while on La-Ru-O/Pt/TiO2/SiO2/Si substrates PZT thin films with (111) preferred orientation were obtained. No diffusion of the Ru atoms in the PZT film was found. Ferroelectric response of PZT thin films on these substrates is shown in comparison with the PZT film deposited directly on the Pt/TiO2/SiO2/Si substrate without a La-Ru-O layer.

In previous work, screen-printing technology was used to elaborate an integrated piezoelectric structure on a porous substrate [1]. The substrate was chosen to withstand the film sintering temperature which was lowered at 800degC thanks to the addition of PGO to a PZT composition. The acoustical impedance of this substrate is very close to that of the deposited piezoelectric thick film, making it an adequate backing to deliver a short pulse-echo response, but the resonance frequency is lowered. Intermediate functional layers were necessary between the substrate and the piezoelectric layer. The transducer based on a porous PZT structure including a dense barrier layer and a gold rear electrode is used as a reference device. Here, another set of materials is considered as possible candidate to fulfill both functions of substrate and backing: porous alumina associated with a dense alumina barrier layer and platinum rear electrode. Since the thicknesses of these layers is not negligible compared to the wavelength of the first thickness mode of the piezoelectric layer, they have a relatively strong influence on the electro- acoustic response. The input acoustic impedance of this stack must be controlled very precisely in order to make it an adequate backing The damping of the backing is optimized to deliver a relatively short pulse-echo response, without excessive lowering of the resonance frequency. The piezoelectric thick film on alumina substrate has similar properties to the one on porous PZT. A mean thickness around 30 micrometers and a thickness coupling factor around 40% were obtained in both cases. As a result of the damping, the structure resonates at 40 MHz, the anti-resonance of the piezoelectric thick film alone being around 65 MHz. Pulse-echo measurements allows comparison of the performance of the two devices in terms of sensitivity, axial resolution and bandwidth. The results are compared and discussed, showing that the sensitivity/bandwidth trade-offs of the two transducers are significantly different.

International audience; As a lead-free candidate for electronic application, Na0.5Bi0.5TiO3 (NBT) thin films were produced by a 2-methoxyethanol sol–gel route and CSD method. Thermal decomposition and crystallization pathway of the alkoxide-based precursor have been studied by thermal analysis and X-ray diffraction (XRD) techniques. No transitory nanocrystalline phase was detected during the crystallization process of NBT. As a consequence, the nucleation of the stable perovskite phase occurred at low temperature (