Journal of the Korean Ceramic Society

Kim, Hyojung; Im, In Hyuk; Hyun, Daijoon; Hilal, Muhammad; Cai, Zhicheng; Yang, Seok Joo; Shim, Young-Seok; Moon, Cheon Woo

doi: 10.1007/s43207-025-00497-ypmid: N/A

Smart healthcare and medical services have been among the fastest-growing AI applications. Stretchable electronics are being considered for flexible/stretchable paper displays, wearable computers, artificial electronic skin, and biomedical devices. Complex and dynamic mechanical environments in wearable applications that demand conformation and conformance necessitate stretchable electronic devices with malleable, mechanical properties. Exploring and discovering devices are popular, because electronic devices need flexible memory to store and retrieve data. The resistive switching memory device is the ideal contender for stretchable memory because of its basic metal–insulator–metal structure and the benefits of the patterned and crossbar-structured memory generated by oxygen vacancies and conductive metal filaments. Stretchable electronics and manufacturing methods are appealing, because wearable and integrated electronics systems are in demand. More innovative materials and device architecture have increased electronic device adaptability and lower production costs. This paper describes wearable and stretchable resistive switching memory device structures and materials. Next, it explains their operation and resistive switching. Also introduced are stretchable resistive switching memory electrodes, insulating layers, crossbar array topologies, and artificial synapse memristors. Moreover, stretchable memristors are utilized in smart sensor systems for data processing and storage. They can be employed in environmental sensors or biosensors to enhance signal processing and data storage. The stretchable memristor, now in its initial stage of development, exhibits significant potential and opportunity for enhancement. This early stage highlights the potential for significant progress shortly.

Ötenkaya, Şaban; Ünal, Rahmi

doi: 10.1007/s43207-025-00501-5pmid: N/A

Ceramic materials are widely used in engineering due to their superior mechanical properties, such as higher strength, thermal stability, and wear resistance. Achieving high surface integrity in ceramic components is still a challenge due to the damage induced during machining, particularly grinding. Thus, this review will provide a thorough overview of how surface roughness (SR) and subsurface damage (SSD) are formed by discussing the effects of various grinding parameters on surface integrity. The review highlights the transition from brittle fracture to ductile material removal mechanisms and the rising effect of critical cutting parameters, including undeformed chip thickness, grinding forces, and particular energy on defects on the surface. The influence on mechanical properties, fracture behavior, and change in micro-hardness caused by grinding induced by structural defects are also analyzed. In particular, various destructive and non-destructive damage assessment methods are evaluated against their efficiency in characterizing SSD. The intricate relationship between SR and SSD is critically assessed and emphasizing the need for more robust predictive models. Finally, the challenges in optimizing ceramic grinding processes are briefly explained, along with potential suggestions for future research directions regarding the machining efficiency and performance of advanced ceramics in industrial applications.

Cho, Hyungyu; Park, Hyunjin; Seon, Seungchan; Kim, BeomSoo; Park, Okmin; Kim, TaeWan; Kim, Hyun-Sik; Kim, Sang-il

doi: 10.1007/s43207-024-00456-zpmid: N/A

Bi2Se3 alloys are considered promising thermoelectric materials for application at ambient to moderately high temperatures. However, because of the narrow band gap (Eg) of Bi2Se3-based materials, bipolar conduction dominates and impairs their thermoelectric performance at elevated temperatures. In this study, we investigated the electrical and thermal transport properties of Bi2Se3 alloyed with indium (In) by incorporating as much as 50% In in the ((Bi1-xInx)2Se3, where x = 0, 0.125, 0.25, 0.375, and 0.5) compositions, which widen the Eg of the Bi2Se3. Analysis of the activation energy, the Goldsmid−Sharp Eg, and optical Eg revealed that Eg might gradually become wider with increasing In content. This gradual widening of Eg led to a corresponding gradual decrease in the carrier concentration. However, the heaving doping of In induces an exponential decrease in the mobility, which resulted in an significant decrease in the electrical conductivity and power factor. The lattice thermal conductivity decreased significantly owing to strong phonon scattering by the heavy In doping and the bipolar thermal conductivity appeared to be reduced. Overall, a thermoelectric figure of merit is significantly reduced for the heavily In-doped Bi2Se3 mainly due to significant reduction of the mobility. Although the significant reduction in κlatt and κbp was observed. Therefore, further theoretical analysis based on a two-band model was performed to further investigate the estimated correlation on the electrical and thermal transport properties of Bi2Se3 and its Eg.

Shin, Jiyeon; Hwang, Jeong Yun; Kim, Changyu; Park, Jimyeong; Mirzaei, Ali; Roh, Jong Wook; Lee, Se Hun; Jin, Changhyun; Choi, Myung Sik

doi: 10.1007/s43207-025-00479-0pmid: N/A

In this work, we investigated the effects of microwave (MW) irradiation and the rotational hydrothermal method on SnO2-ZnO nanocomposites for NO2 gas detection by comparing commercial SnO2 nanoparticles (NPs), SnO2-ZnO nanocomposites, and MW-irradiated SnO2-ZnO nanocomposites. Initially, a novel rotational hydrothermal method, involving exposure to temperatures of 180 °C for 24 h, was used to synthesize SnO2-ZnO nanocomposites, which were then subjected to MW irradiation in 30 s intervals for a total of 10 cycles. The crystalline phase, morphology, chemical composition, physical effects of MW irradiation, and oxygen vacancies of the nanocomposite synthesized were thoroughly analyzed for the first time using MW irradiation and rotational hydrothermal methods. At 250 °C, the MW irradiated sensor recorded a response of 62.1 to 10 ppm NO2 gas and response and recovery times of 257 s and 57 s, respectively. Furthermore, the sensor demonstrated high long-term stability and high selectivity to NO2 gas. The improved NO2 performance of the optimized sensor was related to the physical effects of MW irradiation and oxygen vacancies as well as the formation of ZnO-SnO2 heterojunctions. We successfully presented a novel synthesis route for the preparation of nanocomposites and demonstrated the strong effect of MW irradiation on NO2 sensing performance.

Mahmoud, Hatem A.; Ali, Tarek T.; Nasr, Shereen A. E.; Mahmoud, Esraa A. A.; Nassr, Lobna A. E.; Mohamed, Ibrahim M. A.

doi: 10.1007/s43207-024-00472-zpmid: N/A

Novel photocatalytic metal–organic framework (MOF) materials are an exciting research topic. However, the lack of investigating rare-earth doped semiconductor as well as understanding their physicochemical and structural characterization will prevent commercial or industrial applications. To overcome this obstacle, this study investigates the physicochemical and structural characterization of novel applied Titania-based materials synthesized via MOF strategy for photodegradation of methyl orange (MO). The studied materials are TiO2, Pr-doped TiO2 (Pr@TiO2), and Nd-TiO2 (Nd@TiO2) and applied as promising photocatalysts. The synthesized photocatalysts were prepared via metal–organic framework strategy and characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). SEM analysis revealed that only Nd resulted in smaller, more uniform particle sizes. XRD patterns confirmed the retention of the anatase phase in the case of Nd-modification, indicating successful lattice distortions. XPS results showed the chemical existence of Pr and Nd, increased oxygen vacancies, and surface hydroxyl groups, essential for enhanced photocatalytic activity. Photodegradation studies demonstrated that both Pr-TiO2 and Nd-TiO2 exhibited better performance compared to TiO2 without Pr or Nd, following pseudo-first-order kinetics. These findings highlight the potential of Pr and Nd modification in the TiO2 photocatalysts for efficient environmental remediation, particularly in the treatment of dye-containing wastewater.

Hong, Hyun Seon; Kim, Yerin; Kim, Jea Hyung; Ryu, Hyeon Seon; Song, Dahye

doi: 10.1007/s43207-025-00480-7pmid: N/A

Long-term stable manganese ion-doped ZnSe/ZnS quantum dots were prepared through an internal doping strategy. The internal doping method consisted of nucleation of MnSe core particles, exchange of manganese ions for zinc ions, and formation of an external layer of ZnSe in an aqueous solution. The internally doped Mn:ZnSe showed excellent optical properties compared with those of external doping or interfacial doping; 31% increase in photo-luminescence (PL) intensity. To optimize multiple emission peaks and color purity, varying the Mn/Zn ratio, controlling pH, and multi-step injection of Zn precursor were used. The resulting quantum dots exhibited high color purity of 96% while suppressing trap emission. The highest photo-luminescence was achieved when the molar ratio of Mn to Zn was 0.02. It was also revealed that the presence of the ZnS shell of the Mn2+-doped quantum dots enhanced the long-term stability of the quantum dots up to at least 80 days. This study implies the non-toxic and facile synthesis of Mn:ZnSe quantum dots by internal doping strategy can be an environmentally friendly and highly efficient process of color-controlled ZnSe quantum dots for biomedical imaging applications.

Lucio, Maria Dolores Sosa; Oh, Eun-Ji; Ha, Jang-Hoon; Lee, Jongman; Lee, Hong-Joo; Jung, Seung Hwa; Shin, Jun Young; Song, In-Hyuck; Jeon, Sang-Chae

doi: 10.1007/s43207-025-00492-3pmid: N/A

The processing of millimeter-sized spherical porous ceramic supports, based on encapsulating a solid network within a gelled biopolymer-derived patterning structure, results in particularly interesting advantages. Primarily, it enables the consolidation of ceramic material into a structurally stable body that facilitates handling, separation and cleanliness during application while also enhancing the support’s properties and overall performance. This study focused on the preparation of millimeter-sized spherical porous ZrO2 supports, using ZrO2 powder as the solid network material due to its acid/basic character, thermal stability, and superior chemical stability. Gelled chitosan was employed as the patterning structure, with gelation achieved via a simple pH-triggered process in basic conditions. This approach enabled the fabrication of porous ceramic supports with high sphericity (~ 0.9), optimized solid content (enhancing structural stability), and hierarchical meso/macro porosity, general characteristics preferable for catalytic supports. These features are comparable to those of materials produced using conventional liquid phase-based granulation techniques, which require complex parameter control (e.g., additive content, cooling, and reflux of the feeding broth, and concentration, and temperature of the gelling bath) due to the nature of the processing and the use of precursor-derived solid networks. Thus, the chitosan gelation approach facilitates the granulation process while preserving comparable essential material features. Furthermore, the chitosan gelation mechanism likely minimizes the presence of alkaline and alkaline earth metal by-products within the solid network, which are commonly formed when using alternative biopolymers gelled via ionic cross-linking (e.g., sodium alginate). These by-products can negatively impact catalyst performance by affecting operating temperatures, active sites, and pore accessibility, making gelled chitosan a superior alternative for patterning millimeter-sized spherical porous ceramic supports.

Kato, Takahiro; Iwasa, Yuki; Yokota, Yuui; Ishida, Shigeyuki; Kato, Junichiro; Mino, Yutaro; Naik, S. Pavan Kumar; Horiai, Takahiko; Yoshikawa, Akira; Nishio, Taichiro; Eisaki, Hiroshi; Ogino, Hiraku

doi:

Kim, Hae Jin; Kim, Seung Soo; Park, So Jeong; Oh, Yura; Han, Sua

doi: 10.1007/s43207-025-00491-4pmid: N/A

The electroforming process of the memristor establishes the conduction path and initiates the resistive switching behavior in memristors. However, the conductive paths formed during the electroforming process are hard to control its size and dimension due to the stochastic growth and dissolution, making it challenging to regulate the resistance values and eventually degrading the switching uniformity and reliability. Moreover, in devices requiring electroforming, the initial operating power consumption increases as the array size increases. In this study, a device fabrication process was explored and optimized to annihilate the electroforming step in TiOx/Al2O3 bilayer memristors. By compositional modulation of the switching layer and engineering of the oxide–electrode interface, quasi-electroforming-free switching was achieved, demonstrating a transition from abrupt to gradual resistive switching. The variability in pristine resistance and electroforming voltage was reduced by varying the oxide thickness and the post-annealing conditions. The fabricated devices also exhibited improved resistance modulation under compliance current control, improving the switching uniformity and reliability. Systematic electrical characterization was conducted and the measured electrical properties were analyzed to demonstrate the switching mechanism. This approach significantly improves resistance controllability and reduces switching variability, enabling stable low-power operation. The feasibility of implementation in neuromorphic hardware applications has been also confirmed.

Park, Jeong Yun; Im, Ji Min; Ryu, Bohyun; Baek, Seung-Wook; Kim, Jung Hyun

doi: 10.1007/s43207-025-00495-0pmid: N/A

In this study, the electrochemical and electrical conductivity properties of La0.8Sr0.2MnO3−δ (LSM)-based cathode materials were investigated with respect to different particle sizes and sintering temperatures. XRD analysis showed that LSM-L, synthesized by solid-state reaction, forms the same perovskite single phase as LSM-S. Furthermore, particle-size analysis and powder microstructure analysis verified that LSM-S has a smaller particle size than that of LSM-L. The impedance was measured using LSM cathodes with small- and large-particle sizes. Samples with LSM cathode only, and LSM and YSZ composited in 5:5 and 2:8 ratios, were prepared. Among the three samples, the sample composed of LSM and YSZ in a 5:5 ratio had the lowest area specific resistance (ASR), because it formed the most Triple Phase Boundary (TPB) and exhibited enhanced oxygen reduction reaction (ORR). When LSM and YSZ are composited at a 2:8 ratio, the YSZ particles surround the LSM particles. This limits the transport of electron holes through the LSM, resulting in a lower triple phase boundary (TPB) density. Consequently, the reduction in area-specific resistance (ASR) is minimal when YSZ is used at a higher ratio than LSM, because the decrease in electron hole mobility has a greater impact than the increase in TPB density. The LSM-S cathode, with small particles, which was sintered at 1200 ℃, exhibited the densest microstructure. The highest electrical conductivity value of 186.5 S/cm at 600 ℃ was observed in LSM-S due to the formation of a dense structure, which generated continuous electrical paths and improved the mobility of the charge carriers in the cathodes. In contrast, lower electrical conductivity values were observed in the large-particle LSM. The electrical conductivity was proportional to the sintering temperature. This is due to the increased connectivity between particles at high sintering temperatures, which results in the formation of continuous electrical path. Electrical conductivity was measured by applying currents of 0.1 A, 0.5 A, and 1.0 A. When a current of 0.1 A was applied, the sample exhibited the highest recorded electrical conductivity of 186.5 S/cm. The conductivity values were 163.6 S/cm at 0.5 A and 161.7 S/cm at 1.0 A. LSM-L showed the same behavior. This behavior was attributed to the increase in the path of charge carriers on the cathode surface as the applied current increased.