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"Ru"

A Study on the Explosion Characteristics of Off-Gases from Lithium-Ion Battery Thermal Runaway for EVs Marine Transport Safety
Jeong-hoon Park, In-chul Park
J Electr Electron Mater 2026;39(1):52-58.   Published online January 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.1.6
As electric vehicles (EVs) are rapidly adopted worldwide, large numbers are now transported by sea on dedicated car carriers. With this trend, concerns are increasing about fires and explosions caused by battery thermal runaway during marine transport, while existing SOC limits before loading remain largely empirical. This study experimentally investigates gas generation and explosion characteristics of EV lithium-ion cells under thermal runaway conditions representative of enclosed vehicle decks. We identify and quantify the main off-gas components and clarify the flammability behavior and explosion limits of key combustible species. The results provide basic data for assessing EV battery accidents at sea and support the development of safer ventilation and gas-management strategies for ships.
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A Study on the Development of an Uninterruptible Diagnosis Determination Method for Molded Transformers Using Multiple Diagnosis Sensors
Seok Myung Bae, Yong Moo Chang, Hyo Jin Kim
J Electr Electron Mater 2025;38(5):573-579.   Published online September 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.5.14
With the rapid development of digital technologies such as IoT, AI, and big data, electrical energy consumption is rapidly increasing. Electrical facilities that supply electrical energy are operated with high reliability and stability for end-of-life time. In addition, depending on the type of electrical load that consumes electrical energy in various forms, electrical insulation systems deteriorate due to electrical and thermal stress, which reduces electrical and mechanical insulation strength. Due to such continuous stress and electrical transient phenomena, electrical facilities may experience electrical accidents due to electrical insulation breakdown before the expected design lifetime. In addition, periodic inspections according to related regulations must be conducted to prevent unexpected electrical accidents, but this leads to problems in which the electrical facilities cannot be turned off. Therefore, it is believed that an uninterruptible diagnostic judgment technique that determines compliance with related regulations such as electrical facility technology standards, internal wiring regulations, and inspection regulations without turning off the electrical facilities and at the same time detects abnormal conditions of the facilities early, it is possible to prevent electrical accidents and improve the efficiency of electrical facilities. In this paper, we propose an uninterruptible power diagnosis judgment technique that can prevent or reduce electrical accidents in cast-iron transformers by applying judgment criteria of diagnostic sensors for various types of measurement parameters that can diagnose and evaluate the presence or absence of abnormalities in electrical equipment, including partial discharge, and AI algorithms learned from data of diagnostic sensors.
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Evaluation of Flow Properties of Ceramic Powders Using Static and Dynamic Image Analysis Methods
Ye-won Moon, Hyo-dong Lee, Ji-hui Oh, Jin-ae Kim, Dong-won Lee, Jong-min Oh
J Electr Electron Mater 2025;38(3):254-264.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.3
Ceramic powder is an important material used for various purposes in advanced industries, and the fundamental properties of ceramic powder such as particle size, particle size distribution, and flow properties play a decisive role in determining the quality and performance of the final product. In general, these properties have been evaluated through particle size and shape analysis. However, these methods have limitations in providing a comprehensive understanding phenomena related to powder flow, coagulation, and wear. Consequently, performance evaluation based on the analysis of powder flow properties has been increasingly adopted. Previously, flow properties were primarily assessed using funnel-based methods. However, these methods have limitations, as they are challenging to apply to powders smaller than a few micrometers or those with strong coagulation tendencies, and they also suffer from low reliability. To address these issues, this paper introduces a novel piece of equipment that measures flow properties using image analysis and presents various parameters for static and dynamic flow behavior based on this technique. The proposed equipment offers exceptional versatility, as it can be applied to all types of ceramic powders regardless of their size or shape. The principles and measurement methods of the equipment are demonstrated through static and dynamic image analysis of ceramic powders with varying sizes and shapes used as examples.
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AI Algorithm for Stabilizing Output of Multi-Environment Double-Sided Solar Panels
Jongman Kim, Byonghak Moon, Changyong Jung, Sungjin Park
J Electr Electron Mater 2025;38(2):213-218.   Published online March 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.2.13
We propose a real-time information propagation arithmetic neural network (PANN) that minimizes the loss of power generation output of the system in the event of sudden changes in the module due to strong external typhoons or earthquakes at the solar power generation facility site. In addition, we propose a new double-sided module reflector that can reduce the local loss of power generation efficiency of the single-sided module reflector that is currently widely distributed, as well as the environmental pollution and inconvenience of maintenance work of the existing double-sided module. We present a computational network that can detect the faulty solar panel in real-time by checking the fault status of the installed solar panel and using a real-time computation method through a node-to-node diffusion method. In particular, this method recognizes the power loss part due to sudden changes in the module in real time and can take emergency measures for various nonlinear field facilities through a neural structure that finds the optimal distance up, down, left, and right. To confirm the characteristics of the loss reduction control of the field facility, we confirmed that the system was configured as a 7-degree-of-freedom control model using the PANN neural network learning structure method and improved the power generation output. PANN (Propagation Arithmetic Neural Networks) and various module systems are proposed for the real-time recovery of faulty solar panels and improving module system efficiency.
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Effect of Interface Structure on the Efficiency Enhancement of Al-PDMS Triboelectric Nanogenerator
Dong-woo Hong, Wan-gon Hong, Seung-hun Kim, Sung-nam Lee
J Electr Electron Mater 2025;38(1):107-112.   Published online January 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.1.15
Recent studies have focused on enhancing the efficiency of triboelectric nanogenerators (TENGs) using aluminum (Al) and polydimethylsiloxane (PDMS). This research investigates how surface morphology and material structure affect energy generation. By layering PDMS/Al and creating pyramid-shaped patterns, the study found that increasing the number of PDMS/Al layers significantly boosts the output voltage, reaching over 234 mV with three layers. Additionally, increasing the number of pyramid structures from 1 to 36 on PDMS surfaces, while maintaining the same contact area, led to a notable rise in generated voltage due to charge concentration at the pyramid tips. Higher pyramid angles also amplified this effect. These results highlight the importance of structural optimization in maximizing the energy output of TENGs, offering a promising route for more efficient energy harvesting.
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Analysis of Characteristics of Half-Cut Solar Cells According to the NDC Process for High-Power Modules
Guemhee Ham, Jeahyeong Lee
J Electr Electron Mater 2024;37(6):637-643.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.9
One method to increase the output of solar modules is the application of the Half-cut technique, which requires a scribing process involving direct irradiation of infrared lasers on the solar cells. During this process, the laser melts the surface of the solar cells at high temperatures, enabling mechanical division, but this can lead to output loss due to thermal degradation caused by the laser. To minimize such losses, a low-temperature and low-loss division method has been devised. In this study, we compared the electrical characteristics and leakage currents affecting output degradation between the newly devised low temperature and low-loss cell division method and the conventional laser division method. Additionally, we conducted a 3-point flexural test to evaluate the mechanical properties of both methods.
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Controlled Synthesis of Colloidal Cu Nanowires and Nanoplates and Their Tunable Localized Surface Plasmon Resonances
Seokhwan Kim, Jong Wook Roh, Dong Choon Hyun, Seonhwa Park, Yuho Min
J Electr Electron Mater 2024;37(5):547-553.   Published online September 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.5.12
Precise control over the morphology of nanostructures is critical for tailoring their physical and chemical properties. This study addresses the challenge of developing a simple, integrated method for synthesizing both 1D and 2D colloidal Cu nanostructures in a single system, achieving successful tuning of their localized surface plasmon resonance (LSPR) properties. A facile hydrothermal synthesis utilizing potassium iodide (KI) and hexadecylamine (HDA) is presented for controlling Cu nanostructure morphologies. The key to achieving 1D nanowires (NWs) and 2D nanoplates (NPs) depends on the controlled adsorption of HDA molecules and iodide (I-) ions on specific crystal facets. Depending on the morphologies, the resultant Cu nanostructures exhibit tunable LSPR peaks from 558 nm [nanoplates (NPs)] to 590 nm [nanowires (NWs)]. These results pave the way for the scalable and cost-effective production of plasmonic Cu nanostructures with tunable optical properties, holding promise for applications in sensing, catalysis, and photonic devices.
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Structural and Electrical Properties of K(Ta0.70Nb0.30)O₃/K(Ta0.55Nb0.45)O₃ Heterolayer Thin Films for Electrocaloric Devices
Byeong-jun Park, Ji-su Yuk, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Sung-gap Lee
J Electr Electron Mater 2024;37(3):297-303.   Published online May 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.3.9
In this study, KTN heterolayer thin films were fabricated by alternately stacking films of K(Ta0.70Nb0.30)O3 and K(Ta0.55Nb0.45)O3 synthesized using the sol-gel method. The sintering temperature and time were 750℃ and 1 hour, respectively. All specimens exhibited a polycrystalline pseudo-cubic crystal structure, with a lattice constant of approximately 0.398 nm. The average grain size was around 130~150 nm, indicating relatively uniform sizes regardless of the number of coatings. The average thickness of a single-coated film was approximately 70 nm. The phase transition temperature of the KTN heterolayer films was found to be approximately 8~12℃. Moreover, the 6-coated KTN heterolayer film displayed an excellent dielectric constant of about 11,000. As the number of coatings increased, and consequently the film thickness, the remanent polarization increased, while the coercive field decreased. The 6-coated KTN heterolayer film exhibited a remanent polarization and coercive field of 11.4 μC/cm2 and 69.3 kV/cm at room temperature, respectively. ΔT showed the highest value at a temperature slightly above the Curie temperature, and for the 6-coated KTN heterolayer film, the ΔT and ΔT/ΔE were approximately 1.93 K and 0.128×10-6 K·m/V around 40℃, respectively.
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Structural and Electrical Properties of (La0.7Sr0.3)(Mn1-xFex)O3 Thin Films Prepared by Sol-Gel Method for Thermistor Devices
Ji-su Yuk, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Young-gon Kim, Sung-gap Lee
J Electr Electron Mater 2024;37(2):164-168.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.6
(La0.7Sr0.3)(Mn1-xFex)O3 (LSMFO) (x = 0.03, 0.06, 0.09, 0.12) precursor solution are prepared by sol-gel method. LSMFO thin films are fabricated by the spin-coating method on Pt/Ti/SiO2/Si substrate, and the sintering temperature and time are 800℃ and 1 hr, respectively. The average thickness of the 6-times coated LSMFO films is about 181 to 190 nm and average grain size is about 18 to 20 nm. As the amount of Fe added in the LSMFO thin film increased, the resistivity decreased, and the TCR and B25/65-value increased. Electrical resistivity, TCR and B25/65-value of the (La0.7Sr0.3)(Mn0.88Fe0.12)O3 thin film are 0.0136 mΩ-cm, 0.358%/℃, and 328 K at room temperature, respectively. The resistivity properties of LSMFO thin films matched well with Mott’s VRH model.
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A Study on the Development of Nanorod-Type Ni-Rich Cathode Materials by Using Co-Precipitation Method
Joohyuk Park
J Electr Electron Mater 2024;37(2):215-222.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.14
Ni-rich cathode materials have been developed as the most promising candidates for next-generation cathode materials for lithium-ion batteries because of their high capacity and energy density. In particular, the electrochemical performance of lithium-ion batteries could be enhanced by increasing the contents of nickel ion. However, there are still limitations, such as low structural stability, cation mixing, low capacity retention and poor rate capability. Herein, we have successfully developed the nanorod-type Ni-rich cathode materials by using co-precipitation method. Particularly, the nanorod-type primary particles of LiNi0.7Co0.15Mn0.15O2 could facilitate the electron transfer because of their longitudinal morphology. Moreover, there were holes at the center of secondary particles, resulting in high permeability of the electrolyte. Lithium-ion batteries using the prepared nanorod-type LiNi0.7Co0.15Mn0.15O2 achieved highly improved electrochemical performance with a superior rate capability during battery cycling.
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High Energy Density Dielectric Ceramics Capacitors by Aerosol Deposition
Hyunseok Song, Geon Lee, Jiwon Ye, Ji Yun Jung, Dae-yong Jeong, Jungho Ryu
J Electr Electron Mater 2024;37(2):119-132.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.1
Dielectric ceramic capacitors present high output power density due to the fast energy charge and discharge nature of dielectric polarization. By forming dense ceramic films with nano-grains through the Aerosol Deposition (AD) process, dielectric ceramic capacitors can have high dielectric breakdown strength, high energy storage density, and leading to high power density. Dielectric capacitors fabricated by AD process are expected to meet the increasing demand in applications that require not only high energy density but also high power output in a short time. This article reviews the recent progress on the dielectric ceramic capacitors with improved energy storage properties through AD process, including energy storage capacitors based on both leadbased and lead-free dielectric ceramics.
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A Brief Review on Piezoelectrics-Based Paint Sensors
Hyoung-su Han, Trang An Duong, Chang Won Ahn, Byeong Woo Kim, Jae-shin Lee
J Electr Electron Mater 2023;36(5):433-441.   Published online September 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.5.2
Piezoelectric ceramics play an important role in electrical and electronic devices such as sensors, actuators, and microelectronic devices. However, traditional ceramics are difficult to be used in various process industries due to their high brittleness and low flexibility. Therefore, piezoelectric paint sensors have been designed for application to the curved surfaces of complicated structures. Furthermore, recently, significant attention has been focused on the development of paint sensors that can be used as structure health monitoring sensors for vibration, impact, and acoustic emission. Several studies have successfully demonstrated the possibility that smart paint sensors can take the place of traditional ceramic sensors. In this review, we briefly introduce the concept of the piezoelectric paint sensors and the expected application field as well as their preparation and history.
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Analysis of Power Pattern According to Load Types
Mi-yong Hwang, Seung-joon Cho, Soon-hyung Lee, Yong-sung Choi
J Electr Electron Mater 2023;36(4):369-375.   Published online July 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.4.7
In this paper, we compared and analyzed the power load patterns of dormitory buildings and office buildings to use them as basic data (demand analysis and capacity design) for the design and operation of microgrids for multi-use facilities, and the following conclusions were got. During the daytime on regular weekdays, the power consumption load pattern of office buildings was relatively large at 264.0~332.3 kWh, and during the evening hours, the power consumption load pattern of dormitory buildings was relatively large at 233.0~258.3 kWh. In the case of vacation, during the daytime on weekdays, the power consumption load pattern of office buildings was relatively large at 279.1~407.4 kWh, and in the evening, the power consumption load pattern of dormitory buildings was relatively high at 280.1~394.1 kWh. During the daytime on regular weekends, the power consumption of dormitory-type buildings was relatively high at 133.5~201.6 kWh, and it was found that the power consumption of dormitory-type buildings appeared relatively high at 187.5~252.1 kWh. During a vacation in the daytime on weekends, the power consumption of dormitory-type buildings was found to be 186.5 kWh~ and 218.6 kWh. The increase in power consumption during a vacation (December-February) compared to normal (April-June) was thought to be due to an increase in electricity demand, and the reason for the higher power consumption in dormitory buildings during the vacation was due to reduced working hours in office buildings.
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Structural and Electrical Properties of La0.7Sr0.3-xMgxMnO3 Ceramics with MgO Content
Hyun-tae Kim, Jeong-eun Lim, Byeong-jun Park, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Young-gon Kim, Sung-gap Lee
J Electr Electron Mater 2023;36(3):275-279.   Published online May 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.3.10
La0.7Sr0.3-xMgxMnO3 (LSMMO) (x=0.05~0.20) specimens are fabricated by a solid phase sintering method, and the sintering temperature and time are 1,300℃ and 2 hours, respectively. The dependence of the crystalline structure according to the amount of Mg2+ contents is not observed, and all specimens show a polycrystalline rhombohedral crystal structure, the X-ray diffraction (110) peaks move to the high angle side with increasing the amount of Mg2+ contents. LSMMO specimens exhibit a granule-shaped microstructure with an average grain size of 1 μm or less. Resistivity gradually decrease as the amount of Mg2+ contents increased. And in the La0.7Sr0.1Mg0.2MnO3 specimen, resistivity and B25/65-value are 36.7 Ω-cm and 394 K at room temperature, respectively. LSMMO specimens show a variable-range hopping (VRH) electrical conduction mechanism, and the negative temperature of coefficient of resistance (NTCR) is approximately 0.37~0.38%/℃.
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진공인터럽터의 내전압 성능 향상을 위한 전류컨디셔닝 기법 연구
Young-kwang Cha, Il-hoi Lee, Ki-beom Jeon, Ji-hoon Jang, Heung-jin Ju
J Electr Electron Mater 2022;35(5):480-487.   Published online September 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.5.9
As a process to improve the insulation performance of VIs (Vacuum Interrupters), AC voltage conditioning is generally adopted by many manufacturers. Although the insulation performance is enhanced easily with AC Voltage conditioning, it has limitations when high recovery voltage is required due to high voltage rate or capacitive current switching. In particular, impurities such as oxides segregated on the electrode surface can be removed not by the energy level of the voltage conditioning but by the higher energy level achieved by the current conditioning process In this article, the current conditioning was carried out in various conditions and its validity was examined. The current conditioning was processed by changing the amplitude of applied current, arc time, the number of tests, and frequency. The insulation performance and the status of contact surface were checked as well. We concluded that as the applied charge quantity and the conditioning coverage area increase, the conditioning effect is much higher.
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Structural and Electrical Properties of La0.7Sr0.3MnO3 Thin Films for Thermistor Applications
Jeong-Eun Lim, Byeong-Jun Park, Sam-Haeng Yi, Myung-gyu Lee, Joo-Seok Park, Byung-cheul Kim, Young-gon Kim, Sung-gap Lee
J Electr Electron Mater 2022;35(5):499-503.   Published online September 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.5.12
La0.7Sr0.3MnO3 precursor solution were prepared by a sol-gel method. La0.7Sr0.3MnO3 thin films were fabricated by a spin-coating method on a Pt/Ti/SiO2/Si substrate. Structural and electrical properties with the variation of sintering temperature were measured. All specimens exhibited a polycrystalline orthorhombic crystal structure, and the average thickness of the specimens coated 6 times decreased from about 427 nm to 383 nm as the sintering temperature increased from 740℃ to 830℃. Electrical resistance decreased as the sintering temperature increased. In the La0.7Sr0.3MnO3 thin films sintered at 830℃, electrical resistivity, TCR, B-value, and activation energy were 0.0374 mΩㆍcm, 0.316%/℃, 296 K and 0.023 eV, respectively.
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Synthesis and Characterization of Au@TiO2 Core-Shell Microspheres
Sun-Geum Kim, Ha Jun Jang, Jaewon Jang, Jae-hyun Shim, Sung-june Baek
J Electr Electron Mater 2022;35(4):392-397.   Published online July 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.4.12
We present the structural and optical properties of Au@TiO2 core-shell microsphere structure prepared by a hydrothermal synthesis method. As a way to improve the efficiency of organic solar cells, the Au@TiO2 core-shell microsphere was synthesized to use the local surface plasmon resonance (LSPR) phenomenon. The synthesized results were confirmed to have the Au@TiO2 core-shell structure using a high-resolution transmission electron microscopy. An absorption was observed to occur at 527 nm belonging to the visible light region using a visible light spectroscopy, which supports the LSPR phenomenon. We suggest that the Au@TiO2 core-shell microsphere is highly likely to be applied to organic solar cells including dye-sensitized solar cells. In addition, we expect it to be widely used not only in the energy but also in the bio as well as in the environmental fields.
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Structural and Electrical Properties of (La,Nd,Sr)MnO3 Ceramics for NTC Thermistor Devices
Kyeong-ha Shin, Byeong-jun Park, Jeong-eun Lim, Sam-haeng Lee, Myung-gyu Lee, Joo-seok Park, Sung-gap Lee
J Electr Electron Mater 2022;35(3):292-296.   Published online May 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.3.12
(La0.5Nd0.2Sr0.3)MnO3 specimens were prepared by a solid-state reaction. In all specimens, X-ray diffraction patterns of an orthorhombic structure were shown. The fracture surfaces of (La0.5Nd0.2Sr0.3)MnO3 specimens showed a transgranular fracture pattern be possibly due to La ions (0.122 nm) as a perovskite A-site dopant substituting for Nd ions (0.115 nm) having a small ionic radius. The full-width at half maximum (FWHM) of the Mn 2p XPS spectra showed a value greater than that [8] of the single valence state, which is believed to be due to the overlapping of Mn2+, Mn3+, and Mn4+ ions. The dependence of Mn 2p spectra on the Mn3+/Mn4+ ratio according to sintering time was not observed. Electrical resistivity resulted in the minimum value of 100.7 Ω-cm for the specimen sintered for 9 hours. All specimens show a typical negative temperature coefficient of resistance (NTCR) characteristics. In the 9-hour sintered specimen, TCR, activation energy, and B25/65-value were -1.24%/℃, 0.19 eV, and 2,445 K, respectively.
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Recent Progress in Dielectric Materials for MLCC Application
Intae Seo, Hyung-won Kang, Seung Ho Han
J Electr Electron Mater 2022;35(2):103-118.   Published online March 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.2.1
With the recent increase in demand for electronic devices, multi-layer ceramic capacitors (MLCCs) have become the most important core component. In particular, the next-generation MLCC with extremely high reliability is required for the 4th industrial revolution and electric vehicle applications. Therefore, it is necessary to develop dielectric ceramic materials with high dielectric properties and reliability. During the decades, electrical properties of BaTiO3 based dielectric ceramics, which have been widely used in MLCC industrial field, have been improved by microstructure and defect chemistry control. However, electrical properties of BaTiO3 have reached their limits, and new types of dielectric materials have been widely studied. Based on these backgrounds, this report presents the recent development trends of BaTiO3-based dielectric materials for the nextgeneration MLCCs, and suggests promising candidates to replace BaTiO3 ceramics.
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A Study on the Electrical Characteristics of Ge2Sb2Te5/Ti/W-Ge8Sb2Te11 Structure for Multi-Level Phase Change Memory
Woo-young Oh, Hyun-yong Lee
J Electr Electron Mater 2022;35(1):44-49.   Published online January 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.1.7
In this paper, we investigated current (I)- and voltage (V)-sweeping properties in a double-stack structure, Ge2Sb2Te5/Ti/W-doped Ge8Sb2Te11, a candidate medium for applications to multilevel phase-change memory. 200-nm-thick Ge2Sb2Te5 and W-doped Ge8Sb2Te11 films were deposited on p-type Si(100) substrate using magnetron sputtering system, and the sheet resistance was measured using 4 point-probe method. The sheet resistance of amorphous-phase W-doped Ge8Sb2Te11 film was about 1 order larger than that of Ge2Sb2Te5 film. The I- and V-sweeping properties were measured using sourcemeter, pulse generator, and digital multimeter. The speed of amorphous-to-multilevel crystallization was evaluated from a graph of resistance vs. pulse duration (t) at a fixed applied voltage (12 V). All the double-stack cells exhibited a two-step phase change process with the multilevel memory states of high-middle-low resistance (HR-MR-LR). In particular, the stable MR state is required to guarantee the reliability of the multilevel phase-change memory. For the Ge2Sb2Te5 (150 nm)/Ti (20 nm)/WGe8Sb2Te11 (50 nm), the phase transformations of HR→MR and MR→LR were observed at t<30ns and t<65ns, respectively. We believe that a high speed and stable multilevel phase-change memory can be optimized by the double-stack structure of proper Ge-Sb-Te films separated by a barrier metal (Ti).
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Detection and Analysis of Discharge Pulses by Failure Mechanisms of the Separator inside Lithium-Ion Batteries
Seung-hyun Lim, Gyeong-yeol Lee, Nam-hoon Kim, Dong-eon Kim, Gyung-suk Kil
J Electr Electron Mater 2021;34(5):327-332.   Published online September 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.5.8
Lithium-ion batteries (LIBs) have become a main energy storage device in various applications, such as portable appliances, renewable energy facilities, and electric vehicles. However, the poor thermal stability of LIBs may cause explosion or fire. The thermal runaway is the result of a failure of the separator inside LIB. Damages like tearing, piercing, and collapsing of the separator were simulated in a mechanical, an electrical, and a thermal way, and small discharge pulses of a few mV were detected at the time of separator damages. From the experimental results, this paper provided a method that can identify the separator failure before thermal runaway in the aspect of a potential explosion and fire prevention measures.
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Fabrication of the Solution-Derived BiAlO Thin Film by Using Brush Coating Process for Liquid Crystal Device
Ju Hwan Lee, Dai-hyun Kim
J Electr Electron Mater 2021;34(5):321-326.   Published online September 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.5.7
We fabricated BiAlO thin film by a solution process with a brush coating to be used as liquid crystal (LC) alignment layer. Solution-processed BiAlO was coated on the glass substrate by brush process. Prepared thin films were annealed at different temperatures of 80℃, 180℃, and 280℃. To verify whether the BiAlO film was formed properly, X-ray photoelectron spectroscopy analysis was performed on Bi and Al. Using a crystal rotation method by polarized optical microscopy, LC alignment state was evaluated. At the annealing temperature of 280℃, the uniform homogenous LC alignment was achieved. To reveal the mechanism of LC alignment by brush coating, field emission scanning electron microscope was used. Through this analysis, spin-coated and brush coated film surface were compared. It was revealed that physical anisotropy was induced by brush coating at a high annealing temperature. Particles were aligned in one direction along which brush coating was made, resulting in a physical anisotropy that affects a uniform LC alignment. Therefore, it was confirmed that brush coating combined with BiAlO thin film annealed at high temperature has a significant potential for LC alignment.
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A Study on Polymer Replica Materials for Nanotransfer Printing
Young Lim Kang, Woon Ik Park
J Electr Electron Mater 2021;34(4):262-268.   Published online July 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.4.7
For the past several decades, various next-generation patterning methods have been developed to obtain well-designed nano-to-micro structures, such as imprint lithography, nanotransfer printing (nTP), directed self-assembly (DSA), E-beam lithography, and so on. Especially, nTP process has much attention due to its low processing cost, short processing time, and good compatibility with other patterning techniques in achieving the formation of high-resolution functional patterns. To transfer functional patterns onto desirable substrates, the use of soft materials is required for precise replication of master mold. Here, we introduce a simple and practical nTP method to create highly ordered structures using various polymeric replica materials. We found that polymethyl methacrylate (PMMA), polystyrene (PS), and polyvinylpyridine (PVP) are possible candidates for replica materials for reliable duplication of Si master mold based on systematic analysis of pattern visualization. Furthermore, we successfully obtained well-defined metal and oxide nanostructures with functionality on target substrates by using replica patterns, through deposition and transfer process. We expect that the several candidates of replica materials can be exploited for effective nanofabrication of complex electronic devices.
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Thermal Analysis Characteristics of Vacuum Interrupter for Load Switcher
Kyunguk Jang
J Electr Electron Mater 2021;34(3):209-213.   Published online May 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.3.8
The 22.9 kV vacuum interrupter (VI) built-in load bus switcher (LBS), which is most often used as a load switch for distribution, extinguishes the arc that occurs during normal load opening and closing and fault current interruption within the VI housing to quickly switch circuits. As a protective device for contact separation, the rated current is supplied in a normal state. When a fault current flows due to a fault or an accident in the power system, the contact is disconnected in a vacuum state to block the fault current. In this study, in order to design the optimal VI, the heat dissipation characteristics of VI according to the center electrode distance 0/1/2/3 cm were analyzed by applying the finite element method, and the results were reflected to improve the structure of the VI.
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Evaluation of Breaking Performance of New Contact Material for the Vacuum Interrupter
Young-kwang Cha, Il-hoi Lee, Heung-jin Ju, Tae-yong Shin, Kyong-tae Park
J Electr Electron Mater 2021;34(1):50-55.   Published online January 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.1.9
Copper-chromium alloys have been used as contact materials of vacuum interrupters in circuit breakers, but new materials with highly stable performance are required to break the high voltage and high current barrier due to the recent increase in breaking capacity. In this paper, a new contact material was fabricated from a ternary alloy instead of existing Cu-Cr alloys. Its breaking performance and endurance were verified from a synthetic test and compared with that of various contact materials. The test results verified that the breaking performance of the new contact material was excellent.
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The Formation of Anodic Oxide Film by Anodizing Voltage and Time of 6061 Aluminum Alloy
Youngju Park, Chanyoung Jeong
J Electr Electron Mater 2021;34(1):68-72.   Published online January 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.1.12
Aluminum is a lightweight metal and has excellent properties with regard to conductivity, workability, and strength. It has been used in various industries owing to its economic benefits. To improve upon the mechanical properties and processability by adding various alloying elements to aluminum, improving the corrosion resistance and heat resistance by electrochemically forming a porous anodic film having a thickness and hardness on the surface of the aluminum alloy is crucial. In this study, the aluminum 6061 alloy was controlled by an anodization process in a 0.3M oxalic acid electrolyte at room temperature to investigate the oxide film parameters such as porosity and thickness depending on the modulating applied voltage and time. The anodizing experiment was performed by increasing the time from 1 h to 9 h at 2-h intervals at applied voltages of 50 V and 60 V.
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Study on Formation of Semitransparent Cu Nanoparticle Layers for Realizing Metal Nanoparticle-Dielectric Bilayer Structures
Hye Ryeon Yoon, Yoon Ee Jo, Hoi Jin Yoon, Seung-yun Lee
J Electr Electron Mater 2020;33(6):460-464.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.6
This study reports the fabrication and application of semitransparent Cu nanoparticle layers. Spin coating and subsequent drying of a Cu colloid solution were performed to deposit Cu nanoparticle layers onto Si and glass substrates. As the spin speed of the spin coating increases, the density of the nanoparticles on the substrate decreases, and the agglomeration of nanoparticles is suppressed. This microstructural variation affects the optical properties of the nanoparticle layers. The transmittance and reflectance of the Cu nanoparticle layers increase with increasing spin speed, which results from the trade-off between the exposed substrate area and surface coverage of the Cu nanoparticles. Since the glass substrates coated with Cu nanoparticle layers are semitransparent and colored, it is anticipated that the application of a Cu nanoparticle-dielectric bilayer structure to transparent solar cells will improve the cell efficiency as well as aesthetic appearance.
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Process Development for Enhancement of High Temperature Thermoelectric Properties in a p-Type Skutterudite
Peng Ju Liu, Chang Wan Nou, Soon-mok Choi
J Electr Electron Mater 2020;33(6):495-499.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.12
Power factor improvement at high temperatures has been a major research topic for the development of skutterudite thermoelectric materials. Here, we attempted to optimize the process parameters for manufacturing skutterudite materials, especially for p-type systems. We focused on the effect of aging time variation to maximize the hightemperature performance of the Ce-filled Fe3CoSb12 skutterudite system. The optimized aging time was concluded to be a key parameter for the formation of single-phase nanostructures in this p-type skutterudite system. The optimized condition was effective in reducing the bipolar effect at high temperature ranges by increasing the carrier concentration in the p-type system. To confirm the conclusions, the electrical conductivity, Seebeck coefficient, and power factor were measured. The results matched well with the microstructure and with those of an XRD analysis performed for the system.
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Design for a Fuse of High Durability Protection Elements for Improving the Safety of DC Current Measurement Device
Ye Ji Lee, Jae Seo Youn, Sung Chul Cho, Sung Yeo Noh
J Electr Electron Mater 2020;33(3):201-207.   Published online May 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.3.8
With the expansion in the use of DC power systems and increased need for system maintenance, the development of measurement devices for maintenance requires high stability. Of the different kinds of DC current measurement devices, the single-shot measurement device causes the input signal of the current measuring unit to initially generate a high inrush current. The high inrush current flows into the signal processor of the meter, shortening the life of the internal fuses and causing failure. Therefore, in this study, the I2t value for increasing the durability of the fuse is designed using the available wire diameter. Operating characteristics for 210~400% over-current of the rated current, which is relatively low over-current, are realized by the plating of low melting tin metal. As a result, a method of designing a fuse element for a DC power supply, which improves the safety of the DC current measurement device by blocking the failure caused by the inrush current, is presented.
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Characteristics of SiO2 Based Asymmetric Multilayer Thin Films for High Performance Flexible Transparent Electrodes
Ji-won Jeong, Heon Kong, Hyun-yong Lee
J Electr Electron Mater 2020;33(1):25-30.   Published online January 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.1.6
Oxide (SiO2)/Metal(Ag)/Oxide(SiO2, ITO, ZnO) multilayer films were fabricated using a magnetron sputtering technique at room temperature on Si (p-type, 100) and a glass substrate. The electrical and optical properties of the asymmetric multilayer films depended on the thickness of the mid-layer film and the type of oxide in the bottom layer. As the metal layer becomes thicker, the sheet resistance decreases. However, the transmittance decreases when the metal layer exceeds a threshold thickness of approximately 10~12 nm. In addition, the sheet resistance and transmittance change according to the type of oxide in the bottom layer. If the oxide has a large resistivity, the overall sheet resistance increases. In addition, the anti-reflection effect changes according to the refractive index of the oxide material. The optical and electrical properties of multilayer films were investigated using an ultraviolet visible (UV-Vis) spectrophotometer and a 4-point probe, respectively. The optimum structure is SiO2 (30 nm)/Ag (10 nm)/ZnO (30 nm) multilayer, with the highest FOM value of 7.7×10-3 Ω-1.
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