Lead zirconate titanate ͑PbZr 0.52 Ti 0.48 O 3 − PZT͒ thin films with different thicknesses were deposited on Pt͑111͒ / Ti/ SiO 2 / Si substrates by a sol-gel method. Single perovskite phase with ͑111͒-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly ͑100͒-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Significant differences between the macroscopic and microscopic electrical properties of the films were observed. Those differences can be assigned to changes in the nonswitching film-electrode layer and domain structure.

A highly topical set of perovskite oxides are high-sensitivity piezoelectric ones, among which Pb(Zr,Ti)O3 at the morphotropic phase boundary (MPB) between ferroelectric rhombohedral and tetragonal polymorphic phases is reckoned a case study. Piezoelectric ceramics are used in a wide range of mature, electromechanical transduction technologies like piezoelectric sensors, actuators and ultrasound generation, to name only a few examples, and more recently for demonstrating novel applications like magnetoelectric composites. In this case, piezoelectric perovskites are combined with magnetostrictive materials to provide magnetoelectricity as a product property of the piezoelectricity and piezomagnetism of the component phases. Interfaces play a key issue, for they control the mechanical coupling between the piezoresponsive phases. We present here main results of our investigation on the suitability of the high sensitivity MPB piezoelectric perovskite BiScO3–PbTiO3 in combination with ferrimagnetic spinel oxides for magnetoelectric composites. Emphasis has been put on the processing at low temperature to control reactions and interdiffusion between the two oxides. The role of the grain size effects is extensively addressed.

Single phase Bi 0.7 La 0.3 FeO 3 ceramic samples were successfully synthesized by sol-gel combustion and co-precipitation methods, performing a final sintering at 820-870°C from 10 up to 180 min. Rietveld refinements of the XRD data detected small satellite peaks that were successfully indexed by an incommensurated modulated structure model. Lanthanum doping improves magnetic response, reduces the leakage current and dielectric losses. The piezoelectric coefficient was reported for the first time in the Bi 0.7 La 0.3 FeO 3 composition.

Purpose: The goal of this in vitro study was to identify the topographical features of deproteinized (NaOCl)and etched with phosphoric acid (H3PO4) enamel surface, compared to phosphoric acid surface alone with a Resin Replica model. Materials: Ten extracted lower first and second permanent molars were polished with pumice and water, and then divided into 3 equal buccal sections having similar physical and chemical properties. The enamel surfaces of each group were subjected to the following treatments: Group A: Acid Etching with H3PO4 37% for 15 seconds. Group B: Sodium Hypochlorite (NaOCl) 5.25% for 60 seconds followed by Acid Etching with H3PO4 37% for 15 seconds. Group C; No treatment (control). All the samples were treated as follow: Adhesive and resin were applied to all groups after A, B and C treatment were performed; Then enamel/dentin decalcification and deproteinization and topographic SEM Resin Replica assessment were used to identify resin tags enamel surface quality penetration. Results showed that group B reached an area of 7.52mm2 of the total surface, with a 5.68 mm2 (73%)resin tag penetration equivalent type I and II etching pattern, 1.71 mm2 (26%) equivalent to type III etching pattern and 0.07 mm2 (1%)unaffected surface. Followed by group A with 7.48 mm2 of the total surface, with a 3.47 mm2 (46 %)resin tag penetration equivalent to type I and II etching pattern, 3.30 mm2 (45 %)equivalent to type III etching pattern and 0.71 mm2, and (9 %) unaffected surface. Group C did not show any resin tag penetration. A significant statistical difference (P <0,001) existed between groups A and B in resin quality penetration, leading to the conclusion that when the enamel is deproteinizated with 5.25% NaOCl for 1 minute prior H3PO4,the surface and topographical features of the replica resin penetration surface increases significantly with type I-II etching pattern.

a b s t r a c tIn this work the dielectric behaviour and main features of the phase transition of BaTiO 3 and Ba 0.99 Er 0.01 TiO 3 ceramics were carefully investigated. The temperature and frequency dependences of the dielectric properties of erbium doped BaTiO 3 ceramics were measured in the 25-225 • C and 100 Hz to 10 MHz ranges, respectively. From this study, a dielectric anomaly in the ferroelectric-paraelectric phase transition of the Ba 0.99 Er 0.01 TiO 3 ceramic was observed. The features of the samples phase transition were analysed by using Curie-Weiss, Santos-Eiras' and order parameter local phenomenological models. In the BaTiO 3 system, all models showed a normal phase transition, while was not possible to establish the character of the phase transition in the Ba 0.99 Er 0.01 TiO 3 system. The relaxation parameters of conductive processes for the study ferroelectric materials, analysed in the time domain, did not show any influence on the ferroelectric-paraelectric phase transition. Finally, it was demonstrated that the anomaly observed on the phase transition of the erbium doped BaTiO 3 ceramics is associated with the processes that results in the PTCR effect.

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a b s t r a c tThe temperature and frequency dependences of the undoped BaTiO 3 ceramics dielectric properties were measured between 25 • C and 700 • C and 100 Hz to 10 MHz, respectively. A dielectric anomaly was observed at low frequencies in the temperature range of 400-700 • C. This anomaly was associated to a low frequency dispersion process taking place at high temperature. The relaxation dynamics of the conductive process in BaTiO 3 ceramics was investigated. A relaxation function in the time domain (˚(t)) was determined from the frequency dependence of the dielectric modulus, using a relaxation function in the frequency domain (F*(ω)). In BaTiO 3 ceramics context, the best relaxation functions (F*(ω)), in the temperature ranges of 220-400 • C and 425 • C and 630 • C, were found to be a Cole-Cole and Davidson-Cole distribution functions, respectively. The relaxation function (f(t)) obtained by the time domain method was found to be a Kohlrausch-Williams-Watts (KWW) function type. The activation energy values (0.72 eV and 0.8 eV) reveal a mechanism correlated with the movement of single ionized oxygen vacancies and electrons of the second level of ionization, probably due to the formation of a titanium liquid phase during the sintering process.

A novel and general chemical solution route for processing high-quality transition metal and rare-earth orthorhombic manganite thin films on Pt(111)/Ti/SiO 2 /Si substrates was reported. The precursor solutions decomposition process of the manganites was studied by TG and DTA techniques, showing the formation of the phase above 650°C in LaMnO 3 and 750°C in both EuMnO 3 and DyMnO 3 thin films. X-ray diffraction and Raman spectroscopic analysis reveal the formation of a pure orthorhombic structure, with a space group Pbnm, in LaMnO 3 , EuMnO 3 and DyMnO 3 thin films annealed at temperatures above the TG phase formation temperature observed. Microstructure and grain morphology of the films were analyzed by SEM and AFM techniques, showing a progressive improvement of the films structures with the increase of the annealing temperature. The temperature dependence of the magnetic response of the LaMnO 3 , EuMnO 3 and DyMnO 3 thin films show typical transition temperatures, compared with those reported for lanthanum, europium and dysprosium manganite single crystals and ceramics.