◆ 수열법을 이용한 NaNbO3/KNbO3 나노구조체 합성
: 나노선 직경: ~ 100 nm, 길이: ~ 5 μm
: Nb 금속 분말을 통한 반응시간 단축 (6일 → 12시간)
: 압전 효율 향상을 위한 전도성 기판에 수직 성장 유도
◆ 수열법을 이용한 Na1-xKxNbO3 나노선의 합성 및 합성 메카니즘 규명
◆ Sol-gel법을 이용한 (Na0.5K0.5)(Nb0.7Ta0.3)O3 나노구조체 및 박막 형성
: Nb자리에 Ta를 도핑하여 압전 특성 향상
◆ NKN 박막 형성 연구
: muffling 공정을 통한 특성 향상 및 최적 조건 확립
: 누설전류밀도= 4.218x10-9A/cm2(at 0.2MV/cm2), Ɛr=616.5, d33=74 pm/V
◆ BNT-BT & BNLT-BT 박막의 특성 연구
: 10% Li doped BNBT 박막: Ec 감소 Pr 증가 (우수한 특성 확보)
◆ BNT-BKT-BT & BNRT-BT 박막의 특성 연구
: Na/K의 비율 조절과 Nb자리에 Rb 도핑을 통해 우수한 압전 박막 형성
◆ 박막의 양호한 응력 상태 구현을 위한 LaNiO3/La0.5Sr0.5CO3 도전성 하부전극 제조
: BNT-BT 박막: Ps = 28.3 μC/cm2, Pr = 72.5 μC/cm2, Ec = 121.9 kV/cm
(출처 : 보고서 초록 3p)
Abstract
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IV. Results of research
1. NaNbO3 particles with rhombohedral structure were synthesized using P123 surfactant, and water soluble precursor, Nb-ethoxide. Rhombohedral structure unstable at room temperature was converted to stable orthorhombic structure by additional annealing process.
IV. Results of research
1. NaNbO3 particles with rhombohedral structure were synthesized using P123 surfactant, and water soluble precursor, Nb-ethoxide. Rhombohedral structure unstable at room temperature was converted to stable orthorhombic structure by additional annealing process. In addition, Na2Nb2O6ㆍH2O nanowires were synthesized using Nb powders, NaNbO3 nanowires were synthesized by annealing process to remove the undesirable H2O.
2. KNbO3O nanowires were synthesized by hydrothermal process. Synthesis was conducted with the variables of KOH concentration, temperature, reaction time. Concequently, phase, morphology, change of structure were confirmed. Conversion from orthorhombic to cubic by occurrence of vacancy inside the KNbO3O was confirmed. The vacancy was occurred because of excess amount of K+ ion. In addition, it was reported that tetragonal was converted to orthorhombic by increasing reaction time, because of lattice defect. Uniform, high crystalline KNbO3O nanowires were synthesized with adequate KOH concentration, reaction temperature, time. Eventually, relationship between structure, and properties will be investigated.
3. Synthesized KNbO3O, NaNbO3 nanowires has ~ 100 nm diameter, 4 ~ 5 μm length, and aspect ratio is more than 400.
4. Reported KNbO3O nanowires, and nanoparticles needed 6 days to be synthesized, but we succeeded to reduce the reaction time to 12 hours using more reactive Nb powders. Reduce of reaction time gives simplification of process, increase of economic feasibility. In addition, next research purpose, arraying of nanowires in piezoelectric device, would be solved by vertical growth of nanowires on conductive substrate. Piezoelectric device with arrayed nanowires would be expected to have superior properties than device with randomly oriented nanowires. Moreover, monoclinic structure is available at room temperature, never reported, and it would have superior piezoelectric properties of device than that of orthorhombic structure. Finally, controll of morphology of nanowries, nanoparticles by controlling reaction time.
5. The composition of Na, K was controlled by (Na1-xKx)NbO3(0.0 ≤ x ≤ 0.9). As - synthesized Na2Nb2O6ㆍH2O(SOMS), and Na8Nb6O19ㆍ13H2O were changed to NaNbO3 after annealing process. (Na8xK8-8x)Nb6O19ㆍnH2O is important phase on the synthesize of (Na1-xKx)NbO3, and depending on the ratio of x component, NKN with K-rich, Na-rich were synthesized. Synthesis of NKN nanowires was performed at first in the world, and we obtained generic technology. Moreover, research for synthesis of stoichiometric NKN nanowires, application to energy generating device will be performed.
6. To improve the piezoelectric properties of NKN, this lab doped Ta on Nb-site, finally synthesized NKNT particles. Controll of composition is easy through sol-gel process, not hydrothermal process. Therefore, NKNT nanoparticles, nanotubes, nanowires, thin films which have composition ratio of 0.5 : 0.5 : 0.7 : 0.3, known to have the most good piezoelectric properties, were synthesized. Synthesized nanoparticles have a few tens of nanometers of grain size, pseudocubic structure. Nanowires, nanotubes which have high aspect ratio were synthesized using prepared sol, AAO templates. High aspect ratio was expected to improve piezoelectric properties of generating device. Moreover, spin coating process has advantages of low temperature on the synthesis of thin films. Finally, by controlling spin coating rate, thickness of thin films on various substrates could be controlled.
7. Outstanding NKN thin films were synthesized by sputtering. Na2O was given during 800oC anneling process, consequently fine NKN thin films which have no secondary phases were synthesized. By fine structure, dielectric constant of 237.4, 1.0 x 10-8 A/cm2 (at 0.1 MV/cm2), low leakage current were obtained. In addition, excellent piezoelectric properties of Pr = 21.1μC/cm2, Ec = 31.4 kV/cm, 64.5 pm/V were obtained. On the basis of it, research for piezoelectric device by lifting-off thin films on flexible substrates is being performed.
8. Growth, and properties of NKN thin films depending on annealing condition were investigated. To compensate the volatilization of K+, Na+ during annealing process, injection of Na2O, K2O gas, and NKN muffling process were conducted. Annealed samples on the injection of Na2O, K2O gas formed Na-rich, K-rich NKN thin films, so that outstanding dielectric/piezoelectric properties could not be obtained. In contrast, in the case of thin films which annealed at NKN ambient, almost pure, uniform NKN thin films were synthesized. At the result, it showd outstanding ferroelectric, piezoelectric properties of Leakage current = 0.2 MV/cm2 ~ 4.218 x 10-9 A/cm2, Ɛr=616.5, Pr=11.7 μC/cm2, Ec =133.8 kV/cm, and d33 ==74 pm/V. Consequently, prospective as eco-friendly piezoelectric device which have similar performance with PZT thin films was confirmed.
9. The piezoelectric properties of BNT-BT thin films were significantly decreased by the presence of pyrochlore phase. In addition, BNT-BT thin film had lower piezoelectric properties than bulk material (~160 pC/N) because it had clamping effect of substrate and bottom electrode. Using the Li doping, the 94(Bi0.5Na0.5-xLix)TiO3-6BaTiO3 phases were synthesized from BNT-BT phase which was well known as a MPB composition. 10% of Li doped BNT-BT thin films, which had high piezoelectric properties that compared with BNT-BT thin films.(CaBi4Ti4O15 thin films 65 pm/V, Na0.5K0.5NbO3 thin films 40 pm/V, Bi3.25Nd0.75Ti3O12 thin films 38 pm/V, Bi0.5Na0.5TiO3 thin films 24.8 pm/V) Therefore, 10% of Li doped BNT-BT thin films was expected environment-friendly piezoelectric device.
10. 88(Bi0.5Na0.5TiO3-8(Bi0.5K0.5)TiO5-4BaTiO3 was MPB composition in BNKT-BT system (Na/Kexcesscontent(%) : 0,5, 10, 15, 20, 25).
88(Bi0.5Na0.5)TiO3-8(Bi0.5K0.5)TiO5-4BaTiO3 had ferroelectric properties. Pr was increased with 15% of Na/K excess content, but it was decreased with exceeding 15%.
11. A part of Na+1 site in MPB composition of BNT-BT was displaced by Rb+1 (94(Bi0.5Na0.5-ㅌRbx)TiO3-6BaTiO3). It had highest ferroelectric properties at 5% of Rb doped in 0 V, but Pr was reduced to amount of Rb. Rb doped BNT-BT thin films had high ferroelectric value relatively with BNLT-BT and BNKT-BT.
12. Formed of electrode to LNO, LSCO for maintain the stress condition of BT/BNT-BT thin films : Improve of Ferroelectric properties
- BTO thin films (using LNO electrode): Ps = 17.7 μC/cm2, Pr = 2.5 μC/cm2, Ec = 30.3 kV/cm
- BTO thin films (using LNO and LSCO mixed electrode): Ps = 22.3 μC/cm2, Pr = 6.0 μC/cm2, Ec = 54.1 kV/cm
- BNT-BT thin films (sing LNO and LSCO mixed electrode): Ps = 28.3 μC/cm2, Pr = 72.5 μC/cm2, Ec = 121.9 kV/cm
(출처 : SUMMARY 12~16p)
목차 Contents
- 표지 ... 1제 출 문 ... 2보고서 초록 ... 3요 약 문 ... 4SUMMARY ... 11CONTENTS ... 17목차 ... 19제 1 장 연구개발과제의 개요 ... 21제 2 장 국내외 기술개발 현황 ... 23제 3 장 연구개발수행 내용 및 결과 ... 30 제 1 절 실험방법 ... 30 1. 합성 및 박막 제작 ... 30 2. 물성 측정 ... 32 3. 이론적, 실험적 접근 방법(위탁기관:전북대) ... 33 제 2 절 결과 및 고찰 ... 33 1. NaNbO3 나노입자 및 나노선 ... 34 2. KNbO3 나노선 ... 37 3. Na1-xKxNbO3 나노선 ... 47 4. (Na0.5K0.5)(Nb0.7Ta0.3)O3 나노입자 ... 53 5. Na0.5K0.5NbO3 박막 ... 57 6. (NaxK1-x)(NbyTa1-y)O3 박막 ... 69 7. 위탁기관 연구결과(전북대) ... 70 제 3 절 결 론 ... 96제 4 장 목표달성도 및 관련분야에의 기여도 ... 99제 5 장 연구개발결과의 활용계획 ... 101제 6 장 연구개발과정에서 수집한 해외과학기술정보 ... 102제 7 장 참고문헌 ... 106끝페이지 ... 110
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