In line with the development of electronic devices and technologies, the demand for improving ferroelectric materials’ performance is increasing. Since K0.5Na0.5NbO3 (KNN), an eco-friendly ferroelectric material that does not use lead and has a high Curie temperature, it is attracting attention to its usability as a high-temperature dielectric, and various studies are being conducted to increase performance. In a KNN having a perovskite structure, there was a simulation result that the KNN has higher spontaneous polarization when the A-site in which sodium ions exist is replaced with lithium ions. If the simulation results can be proven experimentally, the application range of KNN-based ferroelectric materials will increase. To this end, we tried to manufacture a K1-xLixNbO3 (KLN) with high electrical characteristics by fabricating niobium-deficient and potassium-excessive compositions, which attempt was made to solve the stoichiometry problem by volatilization and suppress secondary phases. If KLN’s secondary phase suppression and relative permittivity improvement are successful, it will contribute to meeting the demand for developing electronic devices.
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Recent Progress in Relaxor-State Design of BNT-Based Ceramics for High-Efficiency Energy-Storage Capacitors Yeseul Lim, Geon-Tae Hwang Journal of Electrical and Electronic Materials.2026; 39(3): 225. CrossRef
We investigated the origin of magnetic behaviors induced by an asymmetric spin exchange interaction in Fe-site engineered lead iron niobate [Pb(Fe1/2Nb1/2)O3, PFN], which exhibits a room-temperature multiferroicity. The magnitude of spin exchange interaction was regulated by the introduced transition metals with a distinct Bohr magneton, i.e., Cr, Co, and Ni. All compositions were found to have a single-phase perovskite structure keeping their ferroelectric order except for Cr introduction. We discovered that the incorporation of each transition metal imposes a distinct magnetic behavior on the lead iron niobate system; antiferro-, hard ferro-, and soft ferromagnetism for Cr, Co, and Ni, respectively. This indicates that orbital occupancy and interatomic distance play key roles in the determination of magnetic behavior rather than the magnitude of the individual Bohr magneton. Further investigations are planned, such as X-ray absorption spectroscopy, to clarify the origin of magnetic properties in this system.
An all-solid-state electrochromic film was fabricated by laminating tungsten oxide (WO3) and nickel oxide (NiO) thin films deposited by a reactive DC magnetron sputtering on flexible ITO films. The influence of oxygen partial pressure on the crystal structure, microstructure, optical properties, and electrochromic properties of WO3 and NiO thin films were investigated. WO3 and NiO films showed the best electrochromic properties under the flow of Ar:O2=80:20 and Ar:O2=90:10, respectively. The EC film fabricated with an optimized WO3 and NiO films showed a high coloration efficiency, a fast response time, and a stable optical modulation. It is expected that flexible EC window films will pave the way for the next-generation energy-saving windows.
Mg/Al layered double hydroxide with two-dimensional (2D) nanostructures was synthesized by a hydrothermal technique. The morphology and aspect ratio of Mg4Al2(OH)143H2O were controlled by the concentration and kinds of the hydrolysis agent, and temperature. The aspect ratio of Mg4Al2(OH)143H2O layered double hydroxides with the 2D hexagonal crystal structure was tailored from about 12.6 to about 45.7. The intercalated CO32- anions of the synthesized 2D Mg4Al2(OH)143H2O layered double hydroxides were exchanged to NO3- anions. The bulk 2D Mg4Al2(OH)143H2O layered double hydroxides with the increased space between two layers due to the anion exchange were exfoliated in a formamide solution. The aspect ratio of the exfoliated 2D Mg4Al2(OH)143H2O layered double hydroxides increased to 570.3.
An all-transparent ultraviolet (UV) photodetector was fabricated by structuring p-NiO/n-SnO2/ITO on a glass substrate. SnO2 is an important semiconductor material because of its large bandgap, high electron mobility, high transmittance (as high as 80% in the visible range), and high stability under UV light. For these reasons, SnO2 is suitable for a range of applications that involve UV light. In order to form a highly transparent p-n junction for UV detection, SnO2 was deposited onto a device containing NiO as a high-transparent metal conductive oxide for UV detection. We demonstrated that all-transparent UV photodetectors based on SnO2 could provide a definitive photocurrent density of 4 nA cm-2 at 0 V under UV light (365 nm) and a low saturation current density of 2.02 nA × cm-2. The device under UV light displayed fast photoresponse with times of 31.69 ms (rise-time) and 35.12 ms (fall-time) and a remarkable photoresponse ratio of 69.37. We analyzed the optical and electrical properties of the NiO/SnO2 device. We demonstrated that the excellent properties of SnO2 are valuable in transparent photoelectric device applications, which can suggest various routes for improving the performance of such devices.
Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.
A high-performing all-transparent photodetector was created by configuring a MoOx/NiO/ZnO/ITO structure on a glass substrate. The ITO bottom layer was applied as a back contact. To achieve the transparent p/n junction, p-type NiO was coated on the n-type ZnO layer. Reactive sputtering was used to spontaneously form the ZnO or NiO layer. In order to improve the transparent photodetector performance, the functional MoOx window layer was used. Optically, the MoOx window provided a refractive index layer (n=1.39) lower than that of NiO (n=2), increasing the absorption of the incident light wavelengths (λs). Moreover, the MoOx window can provide a lower sheet resistance to improve the carrier collection for the photoresponses. The MoOx/NiO/ZnO/ITO device showed significantly better photoresponses of 877.05 (at λ=460 nm), 87.30 (λ=520 nm), and 30.38 (λ=620 nm), compared to 197.28 (λ=460 nm), 51.74 (λ=520 nm) and 25.30 (λ=620 nm) of the NiO/ZnO/ITO device. We demonstrated the high-performing transparent photodetector by using the multifunctional MoOx window layer.
Transparent UV photodetector was achieved by using wide bandgap metal oxide materials. In order to realize transparent heterojunction UV photodetector, n-type ZnO and p-type NiO metal oxide materials were employed. High light-absorbing SnS layer was inserted into the n-ZnO and p-NiO layers. High-performing UV photodetector was realized by ZnO/SnS/NiO/ITO structures to provide extremely fast response times (Fall time: 7 μ s and rise time: 13 μs) and high rectifying ratio. The use of functional SnS-embedded photodetector would provide a route for high functional photoelectric devices.
NiO serves as a window layer for Si photoelectric devices. Due to the wide energy bandgap of NiO, high optical transparency (over 80%) was achieved and applied for Si photoelectric devices. Due to the high the high mobility, the heterojunction device (Al/n-Si/SiO2/p-NiO/ITO) provide ultimately fast photoresponses of rising time of 38.33 μs and falling time of 39.25 μs, respectively. This functional NiO layer would provide benefits for high-performing photoelectric devices, including photodetectors and solar cells.
We investigated the sintering behavior and piezoelectric properties of lead-free (K0.5Na0.5)NbO3 ceramics co-doped with excess 0.01 mol ZnO and x mol MnO2, where x was varied from 0 to 0.03. Excess MnO2 addition was found to retard the grain growth and densification during sintering. However, 0.005 mol MnO2 addition improved the piezoelectric properties of 0.01 mol ZnO added (K0.5Na0.5)NbO3 ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant d33 of 0.01 mol ZnO and 0.005 mol MnO2 added specimen were 0.40, 304, and 214 pC/N, respectively.
Highly optical transparent photoelectric devices were realized by using a transparent metal-oxide semiconductor heterojunction of p-type NiO and n-type ZnO. A functional template of ITO nanowires (NWs) was applied to this transparent heterojunction device to enlarge the light-reactive surface. The ITO NWs/n-ZnO/p-NiO heterojunction device provided a significant high rectification ratio of 275 with a considerably low reverse saturation current of 0.2 nA. The optical transparency was about 80% for visible wavelengths, however showed an excellent blocking UV light. The nanostructured transparent heterojunction devices were applied for UV photodetectors to show ultra fast photoresponses with a rise time of 8.3 mS and a fall time of 20 ms, respectively. We suggest this transparent and super-performing UV responser can practically applied in transparent electronics and smart window applications.
We investigated the effect of Ta doping on the dielectric and piezoelectric properties oflead-free (K0.5Na0.5)NbO3 ceramics prepared using a conventional ceramic processing. X-ray diffractionanalysis revealed that Ta was perfectly substituted into Nb-sites in the range of 0 to 20 at%. As Tacontent in the KNN increased, the sinterability of KNN ceramics was significantly degraded while the Tadoping enhanced the piezoelectric constant d33, planar mode piezoelectric coupling coefficient (kp), andelectromechanical quality factor (Qm). The highest values for d33, kp, and Qm was found to be 156 pC/N,0.37, and 155, respectively.
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Selection and optimization of Sb and Ta co-doped (K0.41Na0.59)(Nb1-x-ySbxTay)O3 lead-free ceramics Le Tran Uyen Tu, Nguyen Truong Tho Journal of Materials Science: Materials in Electronics.2023;[Epub] CrossRef
We investigated the variation of anion exchange membrane of hydrogen generator of alkaline electrolysis. We detected the variation of elements and change of anion exchange membrane using EDS and FE-SEM. We detected two different sites of membrane because of different structure of membrane. Sp2 shows that the distribution ratio of C, 0, Al is 98% very higher than Sp2 of 78%. Especially, the main elements of STS316 which is P. S. Fe, Ni were more detected at Sp2 than Sp,. We think that this result depends on the structure of membrane. This also affect the resistance, lifetime of membrane and decrease the efficiency of hydrogen production. We hope that this article is a foundation of developing of hydrogen production technology.
Niobium oxide(Nb2O5) films were deposited on p-type Si wafers at room temperature using in-line pulsed-DC magnetron sputtering system with various frequencies. The different duty ratios were obtained by varying the frequency of pulsed DC power from 100 to 300 kHz at the fixed reverse time of 1.5 μs. From the thickness of the sputtered NbOx films, it was possible to obtain much higher deposition rate in case of pulsed-DC sputtering than RF sputtering. However, the similar leakage currents and structural characteristics were obtained from the metal-insulator-semiconductor(MIS) structure fabricated with the NbOx films and the x-ray photoelectron spectroscopy(XPS) results in spite of the different deposition rates. From the experimental results, the NbOx films sputtered by pulsed-DC sputtering are expected to be used in the fabrication process instead of RF sputtering.
In this study we aims to examine the effects of Co3O4 and NiO doping on the defects and electrical properties in ZnO-Bi2O3-Sb2O3 (Sb/Bi=0.5) varistors. It seemed to form □(0.20 eV) and □(0.33 eV) as dominant defects in Co and Ni co-doped ZBS system, however only □appeared in Co- or Ni-doped ZBS. Even though the same defects it was different in capacitance (1.5∼4.5 nF) and resistance (0.3∼9.5 kΩ). The varistor characteristics were improved with Co and Co+Ni doping (non-linear coefficient, α= 36 and 29, relatively) in ZBS. The various parameters (Nd= 1.43∼2.33×1017 cm-3, Nt=1.40∼ 2.28×1012 cm-2, Φb= 1.76∼2.37 V, W= 98∼118 nm) calculated from the C-V characteristics in our systems did not depend greatly on the type of dopant, which were in the range of a typical ZnO varistors. It should be derived a improved C-V equation carefully for more reliable parameters because the variation of the varistor capacitance as a function of the applied dc voltage is depend on the defect, frequency, and temperature.
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Defect-controlled charge transport and switching in PLD-grown Zn0.90Ni0.10O MIS capacitors for non-volatile memory applications Sunena Subhash, Sudheendran Kooriyattil, T.S. Akhil Raman, S. Shyam Shankar, K.C. James Raju Physica B: Condensed Matter.2026; 739: 418941. CrossRef
Lead-free piezoelectric ceramic/epoxy composites with ``0-3`` connectivity were prepared by cold-pressing with a temperature controlled curing method. A ceramic powder with a composition of (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 was synthesized by a conventional solid state reaction route. The dielectric and piezoelectric properties of ceramic/epoxy composites were characterized as a function of the volume fraction (φ) of piezoelectric ceramics, which was varied from 70 to 95vol%. The results indicated that the piezoelectric properties of composites were significantly affected by the volume fraction of ceramics. In terms of the piezoelectric properties, specimens showed the best performance at φ= 85vol%, resulting in the piezoelectric constant d33 of 39pC/N and the figure of merit as a piezoelectric energy harvester (d33·g33) of 1.24 pm2/N.
We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, Ba(Zn1/3Ta2/3)O3 ceramics and their impacts on the microwave dielectric performances using various characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer. According to the measurement of lattice constant changes, anomalous lattice volume contraction of ZrO2 doped Ba(Zn1/3Ta2/3)O3 sample only showed the dielectric quality factor enhancements, which was due to the lattice volume contraction as well as the 1:2 B-site cation ordering. In addition, NiO doping was useful to the stabilization of temperature coefficient of resonance frequency.
A Study of The Surface Dielectric Barrier Discharge Design Conditions for Generating Negative Air Ions Sang-Moon Shin, Jung-Yoon Kim, Jong-Soo Kim, Jae-Ha Choi, Won-Ho Choi Journal of the Korean Institute of Illuminating and Electrical Installation Engineers.2014; 28(1): 114. CrossRef
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