Search results for: Chang-Won Ahn

Items from 1 to 20 out of 102 results

article

Influence of defect chemistry on the electromechanical strain properties of BNT–ST‐based ternary systems

Trang An Duong, Hoang Thien Khoi Nguyen, Till Frömling, Chang Won Ahn, more

Journal of the American Ceramic Society > 107 > 6 > 4170 - 4177

In this study, the stabilization of ergodicity and electromechanical strain properties of lead‐free ternary 0.75Na_1/2Bi_1/2TiO₃–0.24SrTiO₃–0.01ABO₃ piezoceramics (BNT–24ST, ABO₃ = BaZrO₃ (BZ), CaTiO₃ (CT), and BiFeO₃ (BF)) were investigated. The relaxor state could be stabilized in BZ‐and BF‐modified BNT–24ST ceramics even at room temperature, whereas pure BNT–24ST and CT‐modified ceramics exhibited...

article

Clarification on phase transition behaviors by local strain engineering in Bi_1/2Na_1/2TiO₃–SrTiO₃‐based ternary ceramics

Hoang Thien Khoi Nguyen, Trang An Duong, Chang Won Ahn, Byeong Woo Kim, more

Journal of the American Ceramic Society > 106 > 6 > 3622 - 3632

The stabilization of ergodicity plays an important role in realizing large strain in a Bi_1/2Na_1/2TiO₃ (BNT)‐based relaxor, which is strongly related to the degree of random fields with respect to the randomly distributed different cations. To clarify the effects of different ionic radii, this study investigated and compared the microstructures, crystal structures, phase transition behaviors, and electrical...

article

Heteroanionic Lead‐Free Double‐Perovskite Halides for Bandgap Engineering

Chang Won Ahn, Jae Hun Jo, Jin San Choi, Young Hun Hwang, more

Advanced Engineering Materials > 25 > 1 > n/a - n/a

The hetero‐anionic lead‐free double perovskite halides are realized through mechanochemical synthesis by Tae Heon Kim and co‐workers in article number 2201119. The degree of anion substitution is tunable inducing manipulation of the band gaps and the emitted colors of the anionic‐mixed double perovskite halides. The band gap engineering via anion exchange is applicable to fabricate lead‐free optoelectronic...

article

Heteroanionic Lead‐Free Double‐Perovskite Halides for Bandgap Engineering

Chang Won Ahn, Jae Hun Jo, Jin San Choi, Young Hun Hwang, more

Advanced Engineering Materials > 25 > 1 > n/a - n/a

Anion‐substituted lead‐free double perovskite halides through mechanochemical synthesis is realized. According to molar concentration (x), some of the Br atoms in Cs₂AgBiBr₆ are replaced by halogen Cl atoms, which allows us to achieve heteroanionic Cs₂AgBiBr_6−xCl_x. X‐ray diffraction (XRD) analyses show that the as‐synthesized Cs₂AgBiBr_6−xCl_x compounds undergo structural transitions with a shift of...

article

Reversibly Controlled Ternary Polar States and Ferroelectric Bias Promoted by Boosting Square‐Tensile‐Strain

Jun Han Lee, Nguyen Xuan Duong, Min‐Hyoung Jung, Hyun‐Jae Lee, more

Advanced Materials > 34 > 42 > n/a - n/a

Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in multifunctional heterostructures. However, the defect‐dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, deterministic switching between the ferroelectric and...

article

Piezoelectric Nanogenerators: Polarization‐ and Electrode‐Optimized Polyvinylidene Fluoride Films for Harsh Environmental Piezoelectric Nanogenerator Applications (Small 14/2021)

Da Woon Jin, Young Joon Ko, Chang Won Ahn, Sunghoon Hur, more

Small > 17 > 14 > n/a - n/a

In article number 2007289, Jong Hoon Jung, and co‐workers report a highly stable power source application of piezoelectric nanogenerator in the harsh environmental conditions of cryogenic temperatures, low pressures, large temperature/pressure fluctuations, and strong ultraviolet. The polarization‐ and electrode‐optimized ferroelectric polymer‐based piezoelectric nanogenerator can be used in Mars...

article

Polarization‐ and Electrode‐Optimized Polyvinylidene Fluoride Films for Harsh Environmental Piezoelectric Nanogenerator Applications

Da Woon Jin, Young Joon Ko, Chang Won Ahn, Sunghoon Hur, more

Small > 17 > 14 > n/a - n/a

While piezoelectric nanogenerators have demonstrated the effective conversion of tiny mechanical vibrations to electricity, their performances are rarely examined under harsh environmental conditions. Here, a multilayered polyvinylidene fluoride (PVDF) film‐based piezoelectric nanogenerator (ML‐PENG) is demonstrated to generate considerable and stable power outputs even at extremely low temperatures...

article

Large‐Scale Assembly of Peptide‐Based Hierarchical Nanostructures and Their Antiferroelectric Properties

Yonghun Lee, Kyung Won Kim, Nguyen Xuan Duong, Hyeok Park, more

Small > 16 > 45 > n/a - n/a

An effective strategy is developed to create peptide‐based hierarchical nanostructures through the meniscus‐driven self‐assembly in a large area and fabricate antiferroelectric devices based on these nanostructures for the first time. The diphenylalanine hierarchical nanostructures (FF‐HNs) are self‐assembled by vertically pulling a substrate from a diphenylalanine (FF) solution dissolved in a miscible...

article

Constructing Polymorphic Nanodomains in BaTiO₃ Films via Epitaxial Symmetry Engineering

Wei Peng, Jacob A. Zorn, Junsik Mun, Muhammad Sheeraz, more

Advanced Functional Materials > 30 > 16 > n/a - n/a

Ferroelectric materials owning a polymorphic nanodomain structure usually exhibit colossal susceptibilities to external mechanical, electrical, and thermal stimuli, thus holding huge potential for relevant applications. Despite the success of traditional strategies by means of complex composition design, alternative simple methods such as strain engineering have been intensively sought to achieve...

article

Low temperature sintering of lead–free (Bi_1/2Na_1/2)TiO₃-SrTiO₃-BiFeO₃ piezoelectric ceramics by adding excess CuO

Chang-Heon Lee, Hyoung-Su Han, Seong Hyun Kim, Thi Hinh Dinh, more

Journal of Electroceramics > 2018 > 41 > 1-4 > 43-49

This study examined the microstructures, crystal structures, and electrical properties of 0.01 mol CuO–added (1–x)(Bi_1/2Na_1/2)TiO₃–xSrTiO₃–2BiFeO₃ (BNST100x–2BF, x = 0.20 ~ 0.28) ceramics synthesized at two different sintering temperatures. The sintering temperature of the BNST100x–2BF ceramics could be decreased from 1175 °C to 1000 °C by adding a 0.01 mol CuO excess. Low–temperature sintering led...

article

Ferroelectric seeds-induced phase evolution and large electrostrain under reduced poling field in bismuth-based composites

Abdul Khaliq, Muhammad Sheeraz, Aman Ullah, Hae Jin Seog, more

Ceramics International > 2018 > 44 > 11 > 13278- 13285

Bi_0.5Na_0.5TiO₃-based piezoelectric ceramics have attracted great interest in actuator applications due to their high strain response; however, high driving field and large hysteresis of these materials are long-lasting obstacles for their commercial applications. Here, we use a strategy to overcome these hurdles by reducing poling field of the relaxor 0.96Bi_0.5(Na_0.78K_0.22)_0.5TiO₃-0.04Bi(Mg_0.5Ti_0.5...

article

Recent Progress in Potassium Sodium Niobate Lead-free Thin Films

Hae Jin Seog, Aman Ullah, Chang Won Ahn, Ill Won Kim, more

Journal of the Korean Physical Society > 2018 > 72 > 12 > 1467-1483

Lead-free potassium sodium niobate (KNN)-based thin films have attracted much interest in replacing current lead zirconate titanate (PZT)-based piezoelectric thin films in micro electromechanical (MEMS) devices due to the increasing awareness and legislation concerning lead oxide toxicity. Recently, promising piezoelectric performance has been achieved in KNN-based thin films by compositional modification...

article

Effective charge separation in site-isolated Pt-nanodot deposited PbTiO3 nanotube arrays for enhanced photoelectrochemical water splitting

Chang Won Ahn, Pramod H. Borse, Ju Hun Kim, Jae Young Kim, more

Applied Catalysis B: Environmental > 2018 > 224 > C > 804-809

Highly uniform, self-supported PbTiO₃ nanotube arrays are fabricated on a transparent conducting glass by an all solution-based, hard-templating procedure. A new concept of site-isolation has been realized by Pt-sol infiltration only in the internal core of deposited nanotube arrays and thus physically separating electron and hole reaction sites on inside and external surface of the nanotubes, respectively...

article

Erratum to ’ The immune-enhancing activity of Cervus nippon mantchuricus extract (NGE) in RAW264.7 macrophage cells and immunosuppressed mice’ [Food Research International 99 (2017) start 623-629]

Se Hyang Hong, Jin Mo Ku, Hyo In Kim, Chang-Won Ahn, more

Food Research International > 2017 > 102 > C > 793-795

article

Stabilization of the relaxor phase by adding CuO in lead-free (Bi1/2Na1/2)TiO3‒SrTiO3‒BiFeO3 ceramics

Chang‒Heon Lee, Hyoung‒Su Han, Trang An Duong, Thi Hinh Dinh, more

Ceramics International > 2017 > 43 > 14 > 11071- 11077

We investigated microstructures, crystal structures, and electrical properties of high temperature sintered (1‒x)BiNaTiO₃‒xSrTiO₃‒2BiFeO₃ (BNST100x‒2BF, x = 0.20 and 0.22) ceramics without added CuO and compared these results with low temperature sintered BNST100x‒2BF ceramics with 1mol% of added CuO. The sintering temperature and average grain size of BNST100x‒2BF ceramics decreased after addition...

article

The immune-enhancing activity of Cervus nippon mantchuricus extract (NGE) in RAW264.7 macrophage cells and immunosuppressed mice

Se Hyang Hong, Jin Mo Ku, Hyo In Kim, Chang-Won Ahn, more

Food Research International > 2017 > 99 > P1 > 623-629

Chemotherapeutics are often used to inhibit the proliferation of cancer cells. However, they can also harm healthy cells and cause side effects such as immunosuppression. Especially traditional oriental medicines long used in Asia, may be beneficial candidates for the alleviation of immune diseases. Cervus nippon mantchuricus extract (NGE) is currently sold in the market as coffee and health drinks...

article

The effect of high-energy ball milling on the electromechanical strain properties of Bi-based lead-free relaxor matrix ferroelectric composite ceramics

Hyoung-Su Han, Dae-Jun Heo, Thi Hinh Dinh, Chang-Heon Lee, more

Ceramics International > 2017 > 43 > 10 > 7516-7521

The crystal structure, ferroelectric, and electric-field-induced strain (EFIS) properties of Bi-based lead-free ferroelectric/relaxor composite materials are investigated. Bi_1/2(Na_0.82K_0.18)_1/2TiO₃ as a ferroelectric material and 0.98Bi_1/2(Na_0.78K_0.22)_1/2TiO₃‒0.02LaFeO₃ as a relaxor were synthesized via conventional ceramic processing routes while the relaxor (matrix phase) was prepared via high-energy...

article

A study on low sintering-temperature (1 − x)(0.98(Bi_0.5(Na_0.78K_0.22)_0.5TiO₃) − 0.02CuO) − xCoFe₂O₄ particulate composites

Le Thi Mai Oanh, Nguyen Minh, Chang Won Ahn, Aman Ullah, more

Applied Physics A > 2017 > 123 > 7 > 1-6

Low sintering-temperature lead-free particulate composites of (1 − x)(0.98(Bi_0.5(Na_0.78 K_0.22)_0.5TiO₃ − 0.02CuO) − (x)CoFe₂O₄(x = 0–0.15) were synthesized by a combination of sol–gel and solid-state sintering methods. Structural, morphological, ferroelectric, and ferromagnetic properties of the composites were systematically investigated using different techniques. XRD results and FE-SEM images indicated...

article

Large strain in Bi0.5(Na0.78K0.22)0.5TiO3–Bi(Mg0.5Ti0.5)O3 based composite ceramics under low driving field

Abdul Khaliq, Muhammad Sheeraz, Aman Ullah, Jae Shin Lee, more

Sensors and Actuators A: Physical > 2017 > 258 > C > 174-181

The fabricated relaxor/ferroelectric composite showed relaxor and/or ferroelectric phase depending upon the weight content of added Bi_0.5Na_0.5TiO₃ (BNT) seeds. Bi_0.5Na_4.5Ti₄O₁₅ large particles were processed as precursors and modified to BNT plate-like particles by means of a double molten salt method. The base material 0.96Bi_0.5(Na_0.78K_0.22)_0.5TiO₃-0.04Bi(Mg_0.5Ti_0.5)O₃ (BNKT-0.04BMT) was synthesized...

article

Phase transition behavior and mechanical properties of (1-x)(Bi1/2Na1/2)TiO3-xSrTiO3 lead-free piezoelectric ceramics

Sora Jo, Chang-Hyo Hong, Dae Su Kim, Hyung-Won Kang, more

Sensors and Actuators A: Physical > 2017 > 258 > C > 201-207

Lead-free (1-x)(Bi_1/2Na_1/2)TiO₃–xSrTiO₃ (BNST, 0≤x≤0.25) ceramics were prepared by a conventional solid-state reaction. The effect of increasing the concentration of SrTiO₃ (ST) on the phase transition behavior was investigated using x-ray diffraction patterns, field-induced polarization, and strain curves. As the ST concentrations increased, a ferroelectric to ergodic relaxor phase transition occurred...

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Search results for: Chang-Won Ahn

Influence of defect chemistry on the electromechanical strain properties of BNT–ST‐based ternary systems

Clarification on phase transition behaviors by local strain engineering in Bi_1/2Na_1/2TiO₃–SrTiO₃‐based ternary ceramics

Heteroanionic Lead‐Free Double‐Perovskite Halides for Bandgap Engineering

Heteroanionic Lead‐Free Double‐Perovskite Halides for Bandgap Engineering

Reversibly Controlled Ternary Polar States and Ferroelectric Bias Promoted by Boosting Square‐Tensile‐Strain

Piezoelectric Nanogenerators: Polarization‐ and Electrode‐Optimized Polyvinylidene Fluoride Films for Harsh Environmental Piezoelectric Nanogenerator Applications (Small 14/2021)

Polarization‐ and Electrode‐Optimized Polyvinylidene Fluoride Films for Harsh Environmental Piezoelectric Nanogenerator Applications

Large‐Scale Assembly of Peptide‐Based Hierarchical Nanostructures and Their Antiferroelectric Properties

Constructing Polymorphic Nanodomains in BaTiO₃ Films via Epitaxial Symmetry Engineering

Low temperature sintering of lead–free (Bi_1/2Na_1/2)TiO₃-SrTiO₃-BiFeO₃ piezoelectric ceramics by adding excess CuO

Ferroelectric seeds-induced phase evolution and large electrostrain under reduced poling field in bismuth-based composites

Recent Progress in Potassium Sodium Niobate Lead-free Thin Films

Effective charge separation in site-isolated Pt-nanodot deposited PbTiO3 nanotube arrays for enhanced photoelectrochemical water splitting

Erratum to ’ The immune-enhancing activity of Cervus nippon mantchuricus extract (NGE) in RAW264.7 macrophage cells and immunosuppressed mice’ [Food Research International 99 (2017) start 623-629]

Stabilization of the relaxor phase by adding CuO in lead-free (Bi1/2Na1/2)TiO3‒SrTiO3‒BiFeO3 ceramics

The immune-enhancing activity of Cervus nippon mantchuricus extract (NGE) in RAW264.7 macrophage cells and immunosuppressed mice

The effect of high-energy ball milling on the electromechanical strain properties of Bi-based lead-free relaxor matrix ferroelectric composite ceramics

A study on low sintering-temperature (1 − x)(0.98(Bi_0.5(Na_0.78K_0.22)_0.5TiO₃) − 0.02CuO) − xCoFe₂O₄ particulate composites

Large strain in Bi0.5(Na0.78K0.22)0.5TiO3–Bi(Mg0.5Ti0.5)O3 based composite ceramics under low driving field

Phase transition behavior and mechanical properties of (1-x)(Bi1/2Na1/2)TiO3-xSrTiO3 lead-free piezoelectric ceramics

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