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.
The electronic state of Y doped ZnO (YZO) was calculated using the density functional theory. In this study, the program used for the calculation on theoretical structures of ZnO and YZO was Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The detail of electronic structure was obtained by the discrete variational Xα (DV-Xα) method, which is a sort of molecular orbital full potential method. The density of state and energy levels of dopant elements was shown and discussed in association with optical properties, especially related to down-conversion effect. The down-conversion effect of YZO was experimentally investigated by preparing thin films deposited on F doped SnO2 (FTO) glass substrates by sol-gel method using the spin-coating system. A homogeneous and stable solution was prepared by dissolving acetates in the solution added diethanolamine as sol-gel stabilizer. In order to confirm a ultraviolet ray interruption and down-conversion effects, the transmission spectrum and the fluorescent spectrum of YZO films were estimated. The results obtained by experiment were compared with the calculated structure.
We consider Carbon Nanotube (CNTs) counter electrode as alternative material to Platinum counter electrode for dye sensitized solar cells (DSSCs). Also, CNT counter electrodes having different visible light transmittance were prepared on fluorine-doped tin oxide (FTO) glass substrates by spray coating method. Microstructural images show that there are CNT-tangled layers coated on FTO glass substrates. Using such CNT counter electrodes and screen printed TiO2 electrodes, DSSCs were assembled and its I-V characteristics have been studied and compared. Light energy conversion efficiency of DSSCs increased with decreasing in light transmittance of CNT counter electrode. Our result shows that CNT counter electrode is compatible to Pt counter electrode.
Upscaling the dye sensitized solar cell (DSSC) is a key issue that confronting the entry of this type cells in commercial market. Performance of large size DSSCs is always poor than small size cells because of high resistive losses associated with sheet resistance of conducting glass substrates. Here we show a simple method to reduce resistive loss, also, efficient collection of photo generated carriers through silver current collectors which are prepared on both
working electrode and counter electrode substrates by screen printing method in analogy to conventional silicon solar cells. For long-term stability, to protect corrosion and to avoid charge recombination, silver current collectors were laminated by surlyn sheet. Using these substrates, DSSCs were prepared and their I-V characteristics have been studied as a function of light intensity and compared with normal cells which don't have silver carrier collectors.
Multifunction corresponding to multimedia age has furthermore required high integration to the devices at microwave band, so more evolution for multi-layer integration like system on chip(SoC) becomes to be necessary. In wireless mobile communication, portable mobile phones grew up to a huge market. Microwave devices have played an important role in the wireless communication systems. One challenge in the implementation of circuit integration is in the design of micro wave band pass filter with thin film MOM capacitor and spiral inductor. In this paper, Cu and TaO thin film with RF sputtering was deposited for inductor and capacitor on the SiO2/Si(100) substrate. MIM capacitor and spiral inductor was fabricated for L-C band pass filter by sputtering and lift-off. We are analyzed and designed thin films L-C passive components for band pass filter at 900 MHz and 1.8 GHz, an important devices for mobile communication. Based on the high-Q values of passive components, MIM capacitor and spiral inductors for L-C band pass filter, a low insertion loss of L-C passive components can be realized with a minimized chip area. The insertion loss was 3 dB for a 1.8 GHz filter, and was 5 dB for a 900 MHz filter. This paper also discusses a theoretical analysis and practical design to L-C band pass filter.
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.
In this study, spiral inductors on the SiO2/Si(100) substrate were fabricated by the magnetron sputtering method. Cu thin film with the thickness of 0.7~2.0 μm was deposited on the substrate. Square inductors were fabricated through the wet chemical etching technique. The inductors are completely specified by the number of turns, coil width and the coil spacing. Both the width and spacing were varied from 10 to 50 μm and from 20 to 70 μm, respectively. The Frequency dependency of inductance and Q factor were investigated to analyze the performance of spiral inductors.
The design, simulation, modeling and characterization of low-temperature co-fired ceramics (LTCC) RF switch module for GSM band applications were investigated. RF switch circuits were simulated by ADS tool, manufactured using a LTCC multi-layer in the GSM band. It was integrated with low pass filter on switch module. Insertion and return losses at 900 MHz of the low pass filters were designed to lower than 0.3 db and higher than 12.7 db respectively. The RF switch module was constructed, containing 10 embedded passives and 3 surface mounted components integrated on 4.6×4.8×1.2 mm3 volume, 6-layer integrated circuit. The insertion loss of switch module at 900 MHz was about 11~19 db.
For improving solar efficiencies, down conversion of high-energy photons to visible lights is discussed. The losses due to thermalization of charge carriers generated by the absorption of high-energy photons, can largely be reduced in a solar cell if more than one electron-hole pair can be generated per incident photon. The solar cell consists of dye-sensitized anatase-based TiO2, approximately 30 nm particle size, 6 μm thickness, and 6 x 6 mm2 active area, Pt counter electrode and T3/T2 electrolyte. Down conversion phosphor LiGdF4:Eu(LGF) located on the front surface of the solar cells. And we measured the photo-current, current-voltage characteristics, and down-characteristics, and down-conversion efficiency of the down conversion system.
Formation behavior and photo-oxidation abilities of nanostructured TiO2 powders were investigated through a direct
crystallization from aqueous TiOCl2 solutions containing various metal-chlorides at 100°C. The obtained TiO2 powders without any additives and those added with Ni2+, Fe3+ and Nb5+ ions, which have a similar positive ionic radius to Ti4+, were mainly crystallized with rutile phase, whereas those added with Al3+ and Zr4+ ions, which have a quite different positive ionic radius, were mainly crystallized with anatase phase. On the other hand, the secondary particles in the TiO2 powder consisted of acicular and spherical primary particles corresponding to rutile and anatase phases, respectively. From these results, it seems that the positive ionic radius of the additives would affect phase formation as well as morphology of TiO2 precipitates. Among the TiO2 powders prepared, Ni-added powder, which consisted mainly of rutile phase with a small amount of anatase phase, showed excellent photocatalytic ability in decomposition of 4-chlorophenol.
Photo decomposition ability of ultra-fine rutile TiO2 powder was investigated using the photo-catalytic reaction in
aqueous 1.0 mmol 4-chlorophenol (4CP) solutions with pH-controlled conditions. Its photo-catalytic characteristics were
then compared with those of commercial P-25 powder having mainly anatase phase. When 4CP was completely
decomposed by the photo-catalytic reaction, HPPLTed TiO2 powder was more effective than the P-25 powder regardless
of the crystalline structures. As the photo-catalytic reaction time increased, the decomposition of 4CP in the aqueous
solution was accompanied with much consumption of OH- ions. However, in the case of the aqueous solution at pH=4
naturally obtained by mixing of water and 4CP, the photo-catalytic reaction of the HPPLTed TiO2 powder occurred more
actively, compared with in the cases of the more acidic and caustic aqueous solutions. Therefore, it is thought that the
decomposition of non-degradable 4CP would take place well at a certain amount of OH- ion concentration in the aqueous
solution, considering to show no difference in the adsorption of 4CP on the surface of TiO2 particle with various pHs of
the solution, when the HPPLTed TiO2 powder with high surface areas more than 180 m2/g was used.
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.
Angular-dependent magnetoresistance characteristics in Si(001)/NiO(300A)/NiFe(tequals450, 1000, 1350A) thin films was investigated in terms of an angle between current and applied magnetic field. The samples were grown by RF-sputtering and DC-sputtering methods on naturally oxidised Si(001) substrates. First, NiO layer(300A) was grown on Si substrate, followed by the deposition of NiFe layers as a function of NiFe thickness under the condition of in-situ magnetic bias-field of approximately 500G. The measurement of angular magnetoresistance in Si(001)/NiO(300A)NiFe(tequals450, 1000, 1350A) thin films were carried out in variation of an angle between current direction and external magnetic field. Also, on the base of single magnetic domain model, the comparison between the measured and the calculated MR profiles was made. For tNiFe equals 450A, symmetrical MR characteristics were observed as sweeping external magnetic field proceed. However, for tNiFe equals 1000A, asymmetric MR profiles were shown.
Great interest is given in developing magnetoresistance(MR) sensor, using ferromagnetic, electrically non-magnetic conducting and antiferromagnetic films, especially for the use in weak magnetic fields. Here, we report single and Wheatstone-bridge type of MR sensors made in Si(001)/NiO(300A)/NiFe bilayers. Angular dependence of MR profiles was measured in Si(001)/NiO(300A)/NiFe(450A) films as a function of an angle between current and applied field direction, also, linearity was determined. AMR characteristics of single MR sensors was well explained with single domain model. Good linearity in 45 degree(s) Wheatstone-bridge type of MR sensors consisting of 4 single MR sensors made in Si(001)/NiO(300A)/NiFe(450A) was shown in the range of about +/- 50 Oe.