Ferroelectrics, which exhibit electric field dependent dielectric constant, have been of interest for possible applications on electrically controllable devices. Especially, dielectric constant of ferroelectrics could be adjusted in few microseconds to response on externally applied electric field, which made it possible ferroelectrics being used in microwave tunable devices.
In this paper, Effect of BaSrTiO2/Li2CO3 on low temperature sintering and BaSrTiO2/MgO on dielectric property of thick films has been investigated for variable capacitor on RF frequency band. The thick films were fabricated by the tape casting and then the structural and dielectric properties as a function of an addition composition of plastic-sizer ratio and sintering temperature were studied. For the thick film sintered at 1100°C, it was densified to 96 % of BaSrTiO2 theoretical density by the addition of 3 and 10 w% BaSrTiO2/Li2CO3. Dielectric constant increased and tuning range increased with the increased of BaSrTiO2/Li2CO3 content, which probably can be explained by the substitution of Ba3+, Li1+ on BaTiO3 lattice. The tunability and dielectric loss of the BaSrTiO2/Li2CO3 thick film, sintered at 1150°C, were about 43 % and 0.234 at 10~15 MHz respectively. In case of BaSrTiO2/MgO, Dielectric constant decreased and tunability increased with the added of BaSrTiO2/MgO.
Soft magnetic composite materials find increasing use in electrical motors, replacing existing laminate materials. In this study, the composites have been fabricated with micro- and nano-sized highly pure iron powders coated by polyester and phenolic resins. Soft magnetic composite materials have been pressed into ring type for magnetic properties measurement, and bar type for mechanical properties measurement over the pressure range up to 870 MPa. Some
samples have subsequently been heat treated to 300°C. The effect of the amount of organic materials on the magnetic properties like as permeability, magnetic flux density, core loss and green density were investigated. And electrical resistivities were also examined. On the addition of the organic coating materials of 5 wt%, green density of the compacted composites is most high of 6.9 g/cm3, and magnetic properties are also better. For the case of 5 wt% polyester resin, the effect of powder size with 100 nm, 3 μm, 10 μm and 53 μm were examined. Both the green density and the magnetic properties are best for the particle size of 10 μm. Fine particles below 3 μm easily agglomerate each other, and
homogeneous coating of each particle surface is difficult.
The goal of this research is to design and evaluate a mutlilayer bender actuator, on a concept that each ceramic layer has different value of piezoelectric d31 coefficient. By stacking the ceramic layers with the different piezoelectric d31 coefficient, the internal stress within the actuator body became maximized. Three type actuators (called as sample 1, 2 and 3) were presented in a specification of stacking ceramic layers with low and high piezoelectric properties. Sample 1 was actuator with high piezoelectricity (d31 = -210pC/N), Sample 2 with low and high piezoelectricities (d31=-100 and -210 pC/N) ), and Sample 3 with low piezoelectricity (d31=-100 pC/N). Sample 2 exhibited higher displacement than the other samples under application of a voltage over 50 V, due to higher internal stress between the top and bottom layers. In addition, high generative force can be expected at the multilayer structure actuator, sample 2, with the two piezoelectric components over actuator with one component.
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