• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.735-738
• /
• 2003

Downsizing electronics requires precision position control with an accuracy of sub-micron order, which demands development of ultra-fine displacive devices. Piezoelectric transducer is one of devices transferring electric field energy into mechanical energy and being capable for fine displacement control. The transducer has been widely used as fine Position control device Multilayer piezoelectric actuator, one of typical piezo-transducer, is fabricated by stacking alternatively ceramic and electrode layers several hundred times followed by cofiring process. Electrode material should be tolerable in the firing process maintaining at ceramic-sintering temperatures up to $1100{\sim}1300^{\circ}C$. Ag-Pd can be used as stable electrode material in heat treatment above $960^{\circ}C$. Besides, adding small quantity ceramic powder allow the actuator to be fabricated in a good shape by diminishing shrinkage difference between ceramic and electrode layers, resulting in avoidance of crack and delamination at and/or nearby interface between ceramic an electrode layers. This study presents synthesis of nano-oxide-added Ag/Pd powders and its feasibility to candidate material tolerable at high temperature. The powders were formed in a co-precipitation process of Ag and Pd in nano-oxide-dispersed solution where Ag and Pd precursors are melted in $HNO_3$ acid.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1997.05a
• /
• pp.111-111
• /
• 1997

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1799-1805
• /
• 2014

In this article, we described about the preparation and electrochemical properties of a flexible energy storage system based on a plastic polyethylene terephthalate (PET) substrate. The PET treated with UV/ozone was fabricated with multilayer films composed of 30 polyaniline (PANi)/graphene oxide (GO) bilayers using layer-by-layer assembly of positively charged PANi and negatively charged GO. The conversion of GO to the reduced graphene oxide (RGO) in the multilayer film was achieved using hydroiodic acid vapor at $100^{\circ}C$, whereby PANi structure remained nearly unchanged except a little reduction of doping state. Cyclic voltammetry and charge/discharge curves of 30 PANi/RGO bilayers on PET substrate (shorten to PANi-$RGO_{30}$/PET) exhibited an excellent volumetric capacitance, good cycling stability, and rapid charge/discharge rates despite no use of any metal current collectors. The specific capacitance from charge/discharge curve of the PANi-$RGO_{30}$/PET electrode was found to be $529F/cm^3$ at a current density of $3A/cm^3$, which is one of the best values yet achieved among carbon-based materials including conducting polymers. Furthermore, the intrinsic electrical resistance of the PANi-$RGO_{30}$/PET electrodes varied within 20% range during 200 bending cycles at a fixed bend radius of 2.2 mm, indicating the increase in their flexibility by a factor of 225 compared with the ITO/PET electrode.

• Journal of the Semiconductor & Display Technology
• /
• v.18 no.4
• /
• pp.100-104
• /
• 2019

The 'ITO/Ag/ITO' multilayers as a highly conductive and transparent electrode, even with the optimum thickness conditions, the transmittances were much lower than those of a single ITO layer on some ranges of the visible wavelength. In order to improve the transmittance, Ag layer was formed with mesh structure. Where, the thickness of the Ag layer was about 10 nm and the space between the Ag lines was varied from 2.9 ㎛ to 19.6 ㎛ with the fixed Ag width of about 1.2 ㎛ in order to vary an open ratio of the Ag mesh structure. The transmittance and sheet resistance in the ITO/Mesh-Ag/ITO multilayer structure were analyzed depending on the open ratio. As a result, a trade off in the open ratio was necessary in order to obtain the transmittance as high as possible and the sheet resistance as possible low. By the open ratio of about 86%, in the ITO/Mesh-Ag/ITO multilayer structure, the transmittance was nearly same as the single ITO layer and the sheet resistance was about 62.3 Ω/.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.36 no.4
• /
• pp.418-421
• /
• 2023

Multilayer Ceramic Capacitors (MLCCs) are essential passive components in the electronics industry, known for their high capacitance due to the multilayer structure comprising inner electrodes and dielectric layers. Nickel electrodes are commonly used in MLCCs as the inner electrodes, and to prevent oxidation during the co-firing of the dielectric layers with nickel electrodes, reducing atmosphere is required. However, reducing atmosphere sintering can also induce a reduction of the dielectric, necessitating precise control of oxygen partial pressure. To explore the possibility of using oxide electrodes that do not require reducing atmosphere sintering, we analyze the electrical properties of nickel oxide (NiO) as a potential candidate. As a preliminary study on its use as an alternative inner electrode, the correlation between microstructure and electrical properties of bulk NiO under different sintering conditions was investigated to gain insights into the conduction mechanisms of the material.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.6
• /
• pp.249-252
• /
• 2011

We investigated the low firing of $Li_2CO_3$ added $0.2Pb(Mg_{1/3}Nb_{2/3})O_3$ - 0.3Pb($Fe_{1/2}Nb_{1/2}$) - $0.5Pb(Zr_{0.475}Ti_{0.525})O_3$ (PMN-PFN-PZT) ceramics and multilayer actuators (MLAs) using Ag inner electrodes. It was found that 0.1 wt% $Li_2CO_3$ was quite effective in lowering the sintering temperature of PMN-PFN-PZT ceramics from $1,100^{\circ}C$ down to $900^{\circ}C$ without deteriorating their piezoelectric ceramics ($d_{33}$ = 425 pC/N and $k_p$ = 61.9%). However, excess $Li_2CO_3$ up to 0.3 wt% brings about unwanted problems such as the formation of a $LiPbO_2$ secondary phase and subsequent degradation in the piezoelectric properties. Using 0.1 wt% $Li_2CO_3$ added PMN-PFN-PZT ceramics, MLAs with Ag inner electrodes were successfully fabricated, resulting in a normalized strain of 580 pm/V at an electric field of 1.5 kV/mm.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2003.10a
• /
• pp.134-135
• /
• 2003

The dental implant materials required good mechanical properties, such as fatigue strength, combined with a high resistance to corrosion. For increasing fatigue resistance and delaying onset of stress corrosion cracking, shot peening has been used for > 50 years to extend service life of metal components. However, there is no information on the electrochemical behavior of shot peened and hydroxyapatite(HA) coated Ti-6Al-4V alloys. To increase fatigue strength, good corrosion resistance, and biocompatibility, the electrochemical characteristics of Ti/TiN/HA coated and shot peened Ti-6Al-4V alloys by electron beam physical vapor deposition(EB-PVD) have been researched by various electrochemical method in 0.9%NaCl. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. The produced materials were quenched at 1000$^{\circ}C$ under high purity dried Ar atmosphere and were hold at 500$^{\circ}C$ for 2 hrs to achieve the fatigue strength(1140㎫) of materials. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. Shot peening(SP) and sand blasting treatment was carried out for 1, 5, and 10min. On the surface of Ti-6Al-4V alloys using the steel balls of 0.5mm and alumina sand of 40$\mu\textrm{m}$ size. Ti/TiN/HA multilayer coatings were carried out by using electron-beam deposition method(EB-PVD) as shown Fig. 1. Bulk Ti, powder TiN and hydroxyapatite were used as the source of the deposition materials. Electrons were accelerated by high voltage of 4.2kV with 80 - 120mA on the deposition materials at 350$^{\circ}C$ in 2.0 X 10-6 torr vacuum. Ti/TiN/HA multilayer coated surfaces and layers were investigated by SEM and XRD. A saturated calomel electrode as a reference electrode, and high density carbon electrode as a counter electrode, were set according to ASTM GS-87. The potentials were controlled at a scan rate of 100 mV/min. by a potentiostat (EG&G Co.273A) connected to a computer system. Electrochemical tests were used to investigate the electrochemical characteristics of Ti/TiN/HA coated and shot peened materials in 0.9% NaCl solution at 36.5$^{\circ}C$. After each electrochemical measurement, the corrosion surface of each sample was investigated by SEM.

• Korean Journal of Optics and Photonics
• /
• v.33 no.1
• /
• pp.28-34
• /
• 2022

We study through computational simulation the focal performance of an infrared (IR) Fresnel lens, composed of a multilayer-graphene zone plate formed under a graphene electrode. Here the Fermi level E_F of the patterned multilayer graphene is adjusted by the overlying graphene electrode. The Fresnel lens effect, with respect to the reflectance contrast between the graphene electrode and the 8-layer graphene zone plate placed on a glass substrate, has been analyzed over a broad wavelength range from 4 to 30 ㎛. As the optimal wavelength of 8 ㎛ (considering the reflectance and the reflectance-contrast ratio) is incident upon the Fresnel lens with a focal length of 240 ㎛, the focal intensity is enhanced by a factor of 4.3 as the E_F of multilayer graphene increases from 0.4 eV to 1.6 eV, and is improved by a factor of 5.8 as the number of graphene layers increases from two to eight. As a result, an all-graphene-based IR Fresnel zone-plate lens, exhibiting multifocal function (240 ㎛ and 360 ㎛) according to the selected E_F, is proposed as an ultrathin lens platform.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.1
• /
• pp.7-11
• /
• 2014

Recently, the buffer layers consisting of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT-PSS) are extensively used to improve power conversion efficiency (PCE) of organic solar cells. However, PEDOT-PSS is not suitable for mass production of organic solar cells due to its intrinsic acid and hygroscopic properties. Moreover, because of chemical reactions between indium tin oxide (ITO) layer and PEDOT-PSS layer, the interface is not stable. For these reasons, alternative materials such as $V_2O_5$ have been developed to be an effective buffer layer. In this work, we used $V_2O_5$/Ag/ITO multilayer structure for the anode buffer layer. With variation of thickness of Ag layer, we investigated the optical and electrical properties of $V_2O_5$/Ag/ITO multi-layer films. As a result, we found that the electrical properties were improved with increasing Ag thickness while optical transmittance decreases in visible wavelength region. From the calculation of figure of merit (FOM) which is used to evaluate proper structure for transparent of optoelectronic, $V_2O_5$/Ag/ITO multilayer electrode was optimized with 4 nm thick Ag layer in optical (88% in transmittance) and electrical ($4{\times}10^{-4}{\Omega}cm$) properties. This indicates that $V_2O_5$/Ag/ITO multilayer electrode could be a candidate for the anode of optoelectronic devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.9
• /
• pp.766-770
• /
• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, $0.07Pb(Mn_{1/3}Nb_{2/3})O_3-xPb(Ni_{1/3}Nb_{2/3})O_3-(0.93-x)Pb(Zr,Ti)O_3$ ceramics system were fabricated using $Li_2CO_3-Bi_2O_3-CuO$ sintering aids and the specimens were sintered at $930^{\circ}C$. Thereafter, their piezoelectric and dielectric characteristics were investigated according to the amount of PNN substitution. At 9 mol% PNN substitution, density, electromechanical coupling factor ($k_p$), dielectric constant, mechanical quality factor ($Q_m$) and piezoelectric constant ($d_{33}$) showed the optimum value of $7.86g/cm^3$, 0.60, 1640, 1323 and 387 pC/N, respectively. It is considered that these values are suitable for piezoelectric divece application such ad multilayer piezoelectric actuator and ultrasonic vibrator with pure Ag internal electrode.