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This article reports about the dielectric and electromechanical properties of sol-gel derived ferroelectric PZT films on metallic substrates. PZT(53/47) films deposited directly on metallic substrates (Hastelloy C-276) show a strong thickness dependence of their dielectric and electromechanical properties as well. This dependence can be described by a model assuming an interface layer between substrate and PZT film. By applying an additional electrode between substrate and PZT film the formation of the interface layer can be minimized and a significant reduction of the thickness dependence as well as a general improvement of the film properties was observed. By varying the Zr/Ti-ratio it was found that the extrema of the dielectric and piezoelectric coefficients are shifted towards Ti-rich stoichiometries compared to bulk ceramics. For PZT thin films with optimized preparation conditions nearly rectangular hysteresis loops with a coercive field strength of 5 V/μm, a piezoelectric coefficient d33 of 96 pm/V and strains up to 0.4% were obtained. Antiferroelectric PZT (98/2) films could be deposited in a good quality on an oxidic electrode, too. The observed field-induced antiferroelectric–ferroelectric phase transition is accompanied by high strains. Furthermore, bending resonance modes of samples with different geometries and the tip displacement of a simple cantilever under a dc-field were investigated. By controlled bending of the substrate charges up to 0.3 μC/cm2 could be obtained. On the other hand, tip displacements of up to 30 μm could be realized by applying a voltage of 17 V/μm, respectively. [Copyright &y& Elsevier]

Ceramic fibers with compositions in the system Si–C have a great potential for high-temperature applications. In recent years, our efforts have been dedicated to the development of polymers consisting of polysilanes suitable to spin fibers and build up matrices for CMC as well. The polysilanes are synthesized via disproportionation of the so-called disilane fraction [Richter, R., Roewer, G., Böhme, U., Busch, K., Babonneau, F., Martin, H.-P. et al., Appl. Organomet. Chem., 1997, 11, 71 (and references cited therein)]. A further thermal treatment yields materials which are soluble in organic solvents, and these solutions can be dry-spun to give fibers which are subsequently pyrolyzed. Solubility and high ceramic yield make this precursor a promising candidate for matrix infiltrations, too. The chemistry and the adjustment of viscosity and solubility to the requirements of the fiber processing as well as the conversion of the dried fibers to pure SiC fibers by thermal treatment will be reported. [Copyright &y& Elsevier]

Abstract: Nd–Mn-doped PZT fibres were produced using the sol–gel process. The PZT was doped with 2mol% neodymium and an amount of 1.1mol% or 0.75mol% manganese. The fibres were investigated with respect to microstructure, composition after sintering and phase content. Strain and polarisation were measured after imbedding the fibres in a polymer matrix. The resulting 1–3-composites were poled with constant electric field. Measurements of strain and polarisation were done using a sinusoidal voltage of high amplitude. Instead of a shifted strain hysteresis (butterfly loop) an asymmetric strain–field relation was observed. The asymmetry depends on the direction of the applied voltage. For the half wave with voltage parallel to former poling voltage the strain curve is linear. For the other half wave the strain curve inflates and there is a region with no change of strain. Possible explanations for the asymmetric strain behaviour are discussed. [Copyright &y& Elsevier]

Sol-gel derived PZT(53/47) fibers with different PbO contents in the spinning sol were sintered with various buffers. Fiber stoichiometry, phase content and microstructure as well as the physical properties of the fibers were investigated. A fully densified microstructure was obtained for fibers 40 μm in diameter sintered as low as 900 °C via (1) an excess PbO content in the spinning sol of 6 mol% or higher and (2) a careful control of the sintering atmosphere by a PbZrO3/PbO buffer. Enhanced porosity was found only for fibers with lower PbO content in the spinning sol or for fibers sintered with PbZrO3/ZrO2 or PbZrO3 buffer, respectively. The densification of PbO-deficient fiber batches is dominated by solid state sintering, while liquid phase sintering is promoted by excess PbO in the system. TEM investigations confirmed the homogeneous nature of the PZT fibers devoid of compositional gradients. Typical dielectric permittivities are in the range of 600–1000, the ferroelectric hysteresis loops are well pronounced with remanent polarization values of about 12 μC/cm2 and coercivities between 1.2 and 1.4 V/μm. Strains of 0.10% were obtained. [Copyright &y& Elsevier]

Provides information on the development of solar anti-reflection (AR) surfaces. Information on the most effective surface developed; Difficulties in developing efficient broadband anti-reflection layers; Investigation of porous sol-gel coatings and subwavelength surface-relief gratings as surfaces with a high solar transmittance.