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Dinh, Thi Hinh,Tran, Vu Diem Ngoc,Nguyen, Thi Thao,Hoang, Quyen Thi Ngoc,Han, Hyoung–,Su,Lee, Jae–,Shin Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.18
<P><B>Abstract</B></P> <P>This study investigated the microstructure, dielectric, ferroelectric, and strain properties of lead‒free 0.995Bi<SUB>1/2</SUB>(Na<SUB>0.82</SUB>K<SUB>0.18</SUB>)<SUB>1/2</SUB>TiO<SUB>3</SUB>–0.005BaZrO<SUB>3</SUB>/0.98Bi<SUB>1/2</SUB>(Na<SUB>0.78</SUB>K<SUB>0.22</SUB>)<SUB>1/2</SUB>TiO<SUB>3</SUB>–0.02LaFeO<SUB>3</SUB> (BNKT18BZ/BNKT22LF) ceramic composites. We found that the required electric field for trigging the phase transition from ergodic relaxor (ER) to ferroelectric of BNKT18BZ/BNKT22LF ceramic composites can be effectively decreased by adding BNKT18BZ as nonergodic relaxor (NER) with changes of three different stabilized regions and the highest <I>S</I> <SUB>usable</SUB> peak points as a function of the applied electric field. The highest <I>d</I> <SUB>33</SUB> <SUP>*</SUP> value of 690p.m./V was obtained at 4kV/mm for 0.3wt BNKT18BZ fraction ceramic composites. This value was higher than 575 p.m./V of BNKT22LF ceramics under an applied electric field of 5kV/mm.</P>
Giant Strain in Lead-free Relaxor/Ferroelectric Piezocomposite Ceramics
Thi Hinh Dinh,Jin-Kyu Kang,Hoang Thien Khoi Nguyen,Trang An Duong,Jae-Shin Lee,Vu Diem Ngoc Tran,Ky Nam Pham 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12
The crystal structural, ferroelectric, and electric-field-induced-strain (EFIS) properties of leadfree relaxor/ferroelectric piezocomposites were investigated. The relaxor-matrix phases were mixed with the ferroelectric-seed phases by using a conventional ceramic processing route. The addition of the ferroelectric seed phase dramatically enhanced the EFIS of the relaxor matrix phase at low electric fields. Giant strains of 745 pm/V at 4 kV/mm and 466 pm/V at 3 kV/mm were obtained when the seed contents were 30 wt% and 50 wt%, respectively, which are much higher than those of the relaxor matrix phase without ferroelectric seeds (575 pm/V at 4 kV/mm and 327 pm/V at 3 kV/mm).
Melvyn WB Zhang,Bach Xuan Tran,Huong Lan Thi Nguyen,Huong Thi Le,Nguyen Hoang Long,Huong Thi Le,Nguyen Duc Hinh,Tran Dinh Tho,Bao Nguyen Le,Vu Thi Minh Thuc,Chau Ngo,Nguyen Huu Tu,Carl A. Latkin,Roger 대한의료정보학회 2017 Healthcare Informatics Research Vol.23 No.2
Objectives: The average alcohol consumption per capita among Vietnamese adults has consistently increased. Although alcoholrelated disorders have been extensively studied, there is a paucity of research shedding light on this issue among Internet users. The study aimed to examine the severity of alcohol-related disorders and other associated factors that might predispose individuals towards alcohol usage in a sample of youths recruited online. Methods: An online cross-sectional study was conducted with 1,080 Vietnamese youths. A standardized questionnaire was used. Respondent-driven sampling was applied to recruit participants. Multivariate logistic and Tobit regressions were utilized to identify the associated factors. Results: About 59.5% of the males and 12.7% of the total youths declared that they were actively using alcohol. From the total sample, a cumulative total of 32.3% of the participants were drinking alcohol, with 21.8% and 25.0% of the participants being classified as drinking hazardously and binge drinkers, respectively. The majority of the participants (60.7%) were in the pre-contemplative stage. Conclusions: A high prevalence of hazardous drinking was recognized among online Vietnamese youths. In addition, we found relationships between alcohol use disorder and other addictive disorders, such as tobacco smoking and water-pipe usage. Our results highlighted that the majority of the individuals are not receptive to the idea of changing their alcohol habits, and this would imply that there ought to be more government effort towards the implementation of effective alcohol control policies.
Kang, Jin-Kyu,Dinh, Thi Hinh,Lee, Chang-Heon,Han, Hyoung-Su,Lee, Jae-Shin,Tran, Vu Diem Ngoc The Korean Institute of Electrical and Electronic 2017 Transactions on Electrical and Electronic Material Vol.18 No.1
A comparative study of microwave and conventional sintering of lead-free $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-BaZrO_3-CuO$ ceramics is presented. It was found that microwave sintering (MWS) can be successfully applied to the fabrication of large strain Bi-perovskite with electric field-induced strains comparable to those obtained with conventional sintering (CFS). Although MWS resulted in smaller grained microstructures than CFS, the ferroelectric properties were stronger in MWS-derived specimens than in the CFS-derived ones. The piezoelectric strain constant $d_{33}{^*}$ of the CFS-derived specimens reached a maximum value of 372 pm/V after sintering at $1100^{\circ}C$, whereas that of MWS-derived specimens peaked at $950^{\circ}C$ with a $d_{33}{^*}$ value of 324 pm/V.
Tran, Vu Diem Ngoc,Ullah, Aman,Dinh, Thi Hinh,Lee, Jae-Shin American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.8
<P>Lead-free piezoelectric [(1-x)Bi-1/2(Na0.82K0.18)(1/2) + xBa]TiO3 ceramics (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized by a conventional solid-state reaction method. The effect of Ba substitution on crystal structure, dielectric, ferroelectric and piezoelectric properties of Bi-1/2(Na0.82K0.18)(1/2)TiO3 (BNKT) ceramic was investigated. A phase transition from the coexistence of rhombohedral and tetragonal to tetragonal phase with the rhombohedral distortion gradually diminished was observed at x = 0.02, and the tetragonality (c/a) was found to increase with increasing Ba content. The temperature and frequency dependence of the dielectric curves exhibited that BNKT-Ba ceramics show relaxor characteristics with diffuse phase transition. However the diffuse character of the ceramics was inhibited with increasing Ba content. The depolarization temperature, T-d increased with increasing Ba substitution. Enhanced remnant polarization and piezoelectric coefficient of 33 mu C/cm(2) and 158 pC/N, respectively were obtained at low substitution of Ba (x = 0.01).</P>
Nga-Linh Vu,Trang An Duong,허대준,Thi Hinh Dinh,안창원,김병우,한형수,이재신 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.5
This study investigated crystal structures, microstructures, and electric-field-induced strain (EFIS) properties of Bibased lead-free ferroelectric/relaxor composites. Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) as a ferroelectric material and 0.78Bi1/2(Na0.78K0.22)1/2TiO3-0.02LaFeO3 (BNKT2LF) as a relaxor material were synthesized using a conventional solid-state reaction method, and the resulting BNKT2LF powders were subjected to high-energy ball milling (HEBM) after calcination. As a result, HEBM proved a larger average grain size of sintered samples compared to conventional ball milling (CBM). In addition, the increased sintering time led to grain growth. Furthermore, HEBM treatment and sintering time demonstrated a significant effect on EFIS of BNKT/BNKT2LF composites. At 6 kV/mm, 0.35% of the maximum strain (Smax) was observed in the HEBM sample sintered for 12 h. The unipolar strain curves of CBM samples were almost linear, indicating almost no phase transitions, while HEBM samples displayed phase transitions at 5~6 kV/mm for all sintering time levels, showing the highest Smax/Emax value of 700 pm/V. These results indicated that HEBM treatment with a long sintering time might significantly enhance the electromechanical strain properties of BNT-based ceramics.
Hong, Young-Hwan,Han, Hyoung-Su,Jeong, Gwang-Hwi,Park, Young-Seok,Dinh, Thi Hinh,Ahn, Chang Won,Lee, Jae-Shin Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.17
<P><B>Abstract</B></P> <P>This study investigated the effect of LiNbO<SUB>3</SUB> modification on the dielectric, ferroelectric and electromechanical strain properties of Bi<SUB>1/2</SUB>Na<SUB>1/2</SUB>TiO<SUB>3</SUB>–SrTiO<SUB>3</SUB> (BNT–ST) lead–free relaxor ceramics. The sintering temperature for lead–free BNT–ST relaxor ceramics was slightly decreased from 1175 °C to 1050 °C by modifying with LiNbO<SUB>3</SUB>. We found that the sintering temperature affects the dielectric behavior of 0.76BNT–(0.24−<I>x</I>)ST–<I>x</I>LiNbO<SUB>3</SUB> (BNST–100<I>x</I>LN) ceramics at high temperature (near dielectric maximum temperature, <I>T</I> <SUB>m</SUB>). The <I>T</I> <SUB>m</SUB> for the low–temperature sintered sample was shifted to relatively higher temperature by comparison with the high–temperature sintered samples. Furthermore, the degradation of dielectric behavior near <I>T</I> <SUB>m</SUB> in low–temperature sintered BNST–2LN ceramics was revealed after poling treatment and seem to be related to the existence of a high temperature stabilized nonergodic relaxor phase. Accordingly, we assume that the stabilized nonergodic relaxor phase is responsible for the relatively late transition from ferroelectrics to the relaxor. Therefore, we obtained the improved <I>d</I> <SUB>33</SUB> <SUP>*</SUP> of 616 pm/V as the highest value in low–temperature sintered BNST–2LN ceramics.</P>