Papers by Keyword: Thick Film

Abstract: Attractive for MEMS, PZT thick films are often microstructured on Si supporting platforms to span the gap between ceramics and thin film technologies. Printing process might lead to lower cost than ceramic process to open routes for MEMS applications. In this paper processing by screen-printing of Au/PZT/Au thick-films supported on alumina or completely released from the substrate are described. Investigations of the film microstructures nevertheless show lower densification than those of bulk ceramics. Prior to selective coating deposition, routes to improve the reduction of the film’s porosity are proposed.

Abstract: Y₂Ti₂O₇ nanoparticles have been synthesized by co-precipitation. Y₂Ti₂O₇ was coated on a glass substrate. The average size of the synthesized Y₂Ti₂O₇ particles and thickness of the coating layer can be controlled by manipulating the relative conditions. The average size of synthesized Y₂Ti₂O₇ nanoparticles was about in the size range of 20 to 30nm with calcination temperature. The effects of synthesis parameters, such as solution pH and calcination temperature, are discussed. The synthesized Y₂Ti₂O₇ nanoparticles were coated on glass substrates by a dip coating process.

Abstract: In this paper, the design and fabrication of a liquid conductivity sensor based on AgPd paste will be described. The device was designed in a four-electrode configuration on a 10 x 25 mm² 96% Al₂O₃ substrate. The distance between the two driving electrodes was 4 mm, whereas the distance between the two measuring electrodes was 2 mm.The device was also integrated with a Ruthenium based temperature sensor printed on the backside of the substrate. Initial characterisation showed that the conductivity sensor has a measured sensitivity and cell constant of 1.67 cm and 0.51 cm^-1, respectively, when a frequency of 1 kHz square wave input was appliedto the driving electrodes. Sensor’s respond variation against temperature was measured around 27.89 μS/°C, corresponding to 2.22 temperature compensation value for salt solution. The results showed a stable response over 5 days measurement cycle, indicating the sensor’s potential for field water quality monitoring application.

Abstract: The magnetic static permeability of sputtered FeCuNbSiB and electrodeposited NiFe patterns with thicknesses varying from 0.1 to 8 μm has been studied. The permeability varies proportionally with the pattern size/thickness ratio, like for uniformly magnetized patterns. Different hypothesis on this variation have been investigated and a critical analysis favors a demagnetizing effect. The comparison between experimental results and the theoretical value of the demagnetizing factor of squares plates confirms MOKE imaging, i.e. large magnetic domains but a non-uniform magnetization in the samples.

Abstract: Barium zirconate titanate, BaZr_xTi_1-xO₃, (BZT) with x compositions have been widely studied as a potential candidate for antenna application. In this study, BZT film was prepared using the electrophoretic deposition (EPD) method. The EPD method was used to produce BZT composite into film for miniaturization purposes and dielectric properties improvement. The EPD process was performed with varying pH, voltages, deposition time and amount of Zr. The results showed that optimum deposition time was obtained at pH 4, 90V and 1 minute deposition time. Increasing Zr content decreased the dielectric constant of the BZT composite, and increased the loss tangent of the samples. The result is in agreement with microstructure observation that Zr addition in BZT decreased the grain size that suppressed the dielectric properties. This makes BZT is a suitable candidate for antenna application.

Abstract: The Solid Oxide Fuel Cell Roll (SOFCRoll) is a novel design based on a double spiral. Combining structural advantages of tubular geometries with processing advantages of thick film methods, it utilises a single cofiring process. The initial concept used separate tape cast layers which were laminated before rolling. To optimise layer thickness to function, thinner screen printed layers were combined into the tape cast structure in 2^nd generation cells. This presented several processing challenges, such as achieving dense electrolyte layers, maintaining porous electrode and current collecting layers and incorporation of integral gas channels. Performance has been promising with open circuit voltages close to 1V and cell power of over 400mW at 800°C, however cracking is still evident. Therefore further iterations are in development where thinner layers are sequentially cast, aiming to improve interfacial bonding and better match plasticity and burn out to reduce cracking. This paper reviews key aspects of understanding and development of the SOFRoll , the challenges that have been tackled and what challenges remain, along with future directions for development and potential applications for this device.

Abstract: M-type barium hexaferrite (BaM) is a promising gyromagnetic material for self-biased microwave\millimeter wave devices because of its large uniaxial magnetocrystalline anisotropy and low microwave loss in high frequency. Due to the limitation of growth conditions, it is difficult to deposit BaM films with enough thickness by PLD, MBE and Magnetron Sputtering for practical application. However, it is demonstrated in present experiment that large area polycrystalline BaM thick films (500μm) with self-biasing (high remanence) and low microwave loss can be successfully fabricated by tape casting. X-ray diffraction and Scanning electron microscopy results indicate that these BaM thick films have highly c-axis oriented crystallographic texture with hexagonal morphology. Magnetic hysteresis loops reveal that samples exhibit excellent properties with a saturate magnetization (4πMs) of 3606G, a high squareness ratio (Mr/Ms) of 0.82. In addition, ferromagnetic resonance (FMR) measurement shows that the FMR linewidth is as small as 431Oe at 48GHz. These parameters ensure these BaM thick films are potentially useful for self-biased microwave\millimeter wave devices such as circulator, phase shifter and filter.

Abstract: This work deals with the new technique employed in the fabrication of thick film which includes material selection, functional materials, milling / drying / pressing, firing and cooling, binder / solvent, substrate preparation, pastes preparation, the screen printing process and drying the sensing layers. A novel approach to electronic nose-head design, using a copper thin film electrode patterning technique was used to deposit electrodes on the alumina substrate. The responses of the sensors to propanol was investigated. The response / recovery times of all the sensors were improved compared to those deposited on glass substrates. For example, the response time for all the NiO / Fe₂O₃ devices at 4000 ppm was less than 10 sec., while the recovery time were 30 sec for both the 75 / 25 and the 50 / 50 mol. % NiO / Fe₂O₃ sensors and 20 sec for the 75 / 25 % NiO / Fe₂O₃ sensor. The response / recovery times of those sensors fabricated on glass substrates were 30 / 45, 45 / 55 and 60 / 85 at the same solvent vapour and concentration.

Abstract: Different ratios of MnO₂ / Fe₂O₃, were used after being fired to form thick film gas sensors. The films were deposited on alumina substrates. The response of the sensors for a concentration range of 2500-5000 ppm increasing by a step size of 500 ppm of propanol at room temperature was investigated. The highest response was with the 75 / 25 MnO₂ / Fe₂O₃ sensor followed by the 25 / 75 and 50 / 50 MnO₂ / Fe₂O₃ sensors. The repeatability of the 75 / 25 mol. % MnO₂ / Fe₂O₃ to propanol at two concentration ranges 500-3000 and 2500 - 5000 ppm increasing with a step size of 500 ppm at room temperature was reported. The X-Ray Diffraction (XRD) is used to determine the final composition of the materials after firing. The XRD results show that MnO₂ reacts with Fe₂O₃ to form FeMn₂O₄ with Fe₂O₃ and Fe₃O₄..

Abstract: 0.67BiFeO₃-0.33BaTiO₃ thick films were prepared by screen printing pastes prepared by kneading the 0.67BiFeO₃-0.33BaTiO₃ powder in a three-roll mill with an organic vehicle. The thick films were fired with Pt bottom electrodes and ZrO₂ substrates to investigate the influence of firing temperature. The microstructures and ferroelectric properties of the thick films were examined and compared with the bulk ceramics. A remanent polarization of 32.0 μC/cm² and coercive field of 28 kV/cm were obtained for a thick film with the addition of 0.5 wt% MnO that was fired at 1050 °C.