• 한국진공학회지
• /
• 제17권5호
• /
• pp.442-447
• /
• 2008

강유전체 0.65Pb$(Mg_{1/3}Ta_{2/3})O_3-0.35PbTiO_3$ 고용체에 $Ag_2O$를 첨가하여 $1200^{\circ}C$에서 소결하여 시료를 제작하였다. 완성된 시료의 미세구조는 주사 전자현미경(SEM)을 이용하여 관찰하였고, 전기적 특성의 관찰을 위하여 유전상수와 유전손실, 초전계수를 측정하였다. 제작된 시료 중에서 0.2 mol%의 $Ag_2O$를 과잉 첨가한 시료에서 유전상수와 초전계수가 가장 크게 나타났다. 각 시료에서 유전상수와 초전계수의 최대값의 온도는 $Ag_2O$ 첨가량이 증가할수록 저온으로 이동하였다.

• 한국전기전자재료학회논문지
• /
• 제13권4호
• /
• pp.312-317
• /
• 2000

Ferroelectric S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ solutions were synthesized using sol-gel process in which strontinum ethoxide bismuth ethoxide trantalum ethoxide were used a s startring materials. SBT thin films were coated on Pt/Ti/ $SiO_2$/Si substrates by spin-coating. rapid thermal annealing (RTA) was used to promote crystallization. Thin films were annealed at $700^{\circ}C$ for 1 hr in an oxygen atmosphere. This temperature is about 10$0^{\circ}C$ lower than the usual annealing temperature for SBT thin films. Pt top-electrode was deposited by sputtering and thin films were post-annealed at $700^{\circ}C$ for 30 min. to enhance electrical properties. As the RTA temperature increased the higher 2 $P_{r}$ values were obtained. At RTA temperature being 78$0^{\circ}C$ remanent polarization of S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ thin film was 7.73 $\mu$C/cm $_2$ and the leakage current density was 1.14$\times$10$^{-7}$ A/c $m^2$ at 3 V. As RTA temperature increased the breakdown voltage was decreased. It is considered that the low-field breadown is caused by the rough surface of SBT films and forming bismuth metal in SBT thin films.films.lms.

• 한국재료학회지
• /
• 제28권9호
• /
• pp.489-494
• /
• 2018

Lead free $(1-x)(0.675BiFeO_3-0.325BaTiO_3)-xLiTaO_3$ (BFBTLT, x = 0, 0.01, 0.02, and 0.03, with 0.6 mol% $MnO_2$ and 0.4 mol% CuO) were prepared by a solid state reaction method, followed by air quenching and their crystalline phase, morphology, dielectric, ferroelectric and piezoelectric properties were explored. An X-ray diffraction study indicates that lithium (Li) and tantalum (Ta) were fully incorporated in the BFBT materials with the absence of any secondary phases. Dense ceramic samples (> 92 %) with a wide range of grain sizes from $3.70{\mu}m$ to $1.82{\mu}m$ were obtained in the selected compositions ($0{\leq}x{\leq}0.03$) of BFBTLT system. The maximum temperatures ($T_{max}$) were mostly higher than $420^{\circ}C$ in the studied composition range. The maximum values of maximum polarization ($P_{max}{\approx}31.01{\mu}C/cm^2$), remnant polarization ($P_{rem}{\approx}22.82{\mu}C/cm^2$) and static piezoelectric constant ($d_{33}{\approx}145pC/N$) were obtained at BFBT-0.01LT composition with 0.6 mol% $MnO_2$ and 0.4 mol% CuO. This study demonstrates that the high $T_{max}$ and $d_{33}$ for BFBTLT ceramics are favorable for industrial applications.

• Transactions on Electrical and Electronic Materials
• /
• 제6권2호
• /
• pp.51-56
• /
• 2005

Ferroelectric Bi$_{3.35}$Sm$_{0.65}$Ti$_{3}$O$_{12}$(BSmT) thin films were synthesized using a sol-gel process. Bi(TMHD)$_{3}$, Sm$_{5}$(O$^{i}$Pr)13, Ti(O$^{i}$Pr)4 were used as the precursors, which were dissolved in 2­methoxyethanol. The BSmT thin films were deposited on Pt/TiO$_{x}$/SiO$_{2}$/Si substrates by spin­coating. The electrical properties of the thin films were enhanced using rapid thermal annealing process (RTA) at 600 $^{circ}$C for 1 min in O$_{2}$. Thereafter, the thin films were annealed from 600 to 720 $^{circ}$C in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The remanent polarization value of the BSmT thin films annealed at 720 $^{circ}$C after the RTA treatment was 35.31 $\mu$C/cmz at an applied voltage of 5 V.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.271-271
• /
• 2006

The structural, dielectric and piezoelectric properties of $[Bi_{1-x}(Na_{0.7-x}K_{0.2}Li_{0.1})]_{0.5}BaxTiO_3$ (BNKLBxT) ceramics were studied for the compositional range, x = 0-0.08. The samples were prepared by conventional sintering technique. The result of X-ray diffraction (XRD) suggest that $Ba^{2+}$ diffuse into the $[Bi(Na_{0.7}K_{0.2}Li_{0.1})]_{0.5}TiO_3$ (BNKLT) lattices to form a solid solution with a single phase perovskite structure. The ceramic show excellent piezoelectric and ferroelectric properties, and optimum properties measured are as follows: piezoelectric constant $d_{33}=230pC/N$, planar electromechanical coupling factor $k_p\;=\;40.3%$, remanent polarization $P_r\;=\;30\;{\mu}C/cm^2$, and coercive field $E_c\; =\;2.5\;kV/mm$, respectively.

• 마이크로전자및패키징학회지
• /
• 제20권4호
• /
• pp.25-30
• /
• 2013

Pb-free ferroelectric $(Na_{0.5}Bi_{0.5})TiO_3$ (NBT) thin films were prepared by a modified sol-gel process. Their structural, dielectric and pyroelectric properties were investigated as a function of the excess Na/Bi ratio and the annealing temperature. In the case of thin films containing no excess Na and Bi, only partial amounts of the perovskite NBT were crystallized, where the films consisted mainly of the pyrochlore phase of $Bi_2Ti_2O_7$ for annealing conditions of $600{\sim}800^{\circ}C$. With increasing excess Na/Bi ratio, the proportion of the perovskite phase effectively increased due to the compensation of the volatile Na and Bi components. For a Na/Bi ratio of 2.0, the thin film with single NBT perovskite phase was obtained within XRD detection limit after annealing at $700^{\circ}C$ for 10 min and it showed the excellent dielectric properties, ${\varepsilon}r$ of ~550 and tan ${\delta}$ of 0.03. While these properties were degraded for Na/Bi ratio of 2.5 despite the existence of pure perovskite phase. The NBT thin film with Na/Bi ratio of 2.0 are also promising candidates for applications requiring pyroelectric devices because it was found to have pyroelectric coefficients of $1.3{\sim}7nC/cm^2K$ in the temperature range of $30{\sim}100^{\circ}C$.

• 한국전기전자재료학회논문지
• /
• 제22권9호
• /
• pp.766-771
• /
• 2009

Lead-free $0.94(Na_{0.5}K_{0.5})NbO_3$-0.06Ba$(Ti_{0.9}Sn_{0.1})O_3$ [0.94NKN-0.06BTS] ceramics doped with 1 mol% $MnO_2$ were synthesized by a conventional solid state method. The phase transitional behavior and piezoelectric properties of the ceramics sintered at various temperatures were investigated. The 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$, having morphotropic phase boundary of orthorhombic and tetragonal phases, exhibited a microstructure with abnormal grain growth. A diffused phase transition behavior for all the specimens was verified as high degree of diffuseness (${\gamma}$) values from 1.45 to 1.79. A high piezoelectric constant of $d_{33}=256$ pC/N and a satisfactory electromechanical coupling factor of $k_p=42%$ were obtained for the relatively dense 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 C
• /
• pp.1242-1244
• /
• 1995

The dielectric and polarizable properties of $0.9Pb_{1-x}La_x({Mg}_{1/3}Nb_{2/3})O_3-0.1PbTiO_3$ (x=0,1,2,3,4,5) have been investigated. The temperature-dependant electrostictive characteristics of 0.9PMN-0.1PT relaxor ferroelectric system were improved by enhencing the extent of the diffuse phase transition(DPT). This was achieved using PMN-PTceramics by the partial substitution of La at the Pb site. The curie temperature and the maximum dielectric permittivity decreased by substituting La and the electric field-related hysteresis phenomena decreased with increasing La substitution amount.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.160-160
• /
• 2009

In recent years, the merging of nanomaterials and nano-technology into electro-optic (EO) device technology such as liquid crystal displays (LCDs) has attracted much attention because of their unique electro- and magneto-optic properties and novel display applications. One example of hybrid LC-inorganic systems is semiconductor nanorods added to LC for their strong reorientation effect and tunable refractive index. Doping of nanoparticles in LC or polymers can lead to changes in performance characteristics such as electro-optical, dielectric, memory effect, phase behavior, etc. Due to the tunability of LCDs with mixed inorganic materials, low voltage operation of a LC system can also be achieved using the significant electro-optical effect achieved through suspension of ferroelectric nanoparticles in NLC.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
• /
• pp.363-366
• /
• 2004

PZT thin films were formed by rf-magnetron sputtering on $Pt/Ti/SiO_2/Si$ substrate. Bulk PZT target containing $5\%$ excess PbO was used. They were formed with in-situ process at $650^{\circ}C$ as total thickness of 175 and 250 nm after the depositing of thin PZT films at room temperature, i. e. 2-step Sputtering. It was found that the ferroelectric perovskite phase is formed at $650^{\circ}C$ by XRD and the interface between room temp.-layer and $650^{\circ}C$ -layer is not existent. In the samples undergoing 2-step sputtering the dielectric constant was 600 or more and the leakage current density was $2{\times}10^{-7}A/cm^2$. So, we found that the room temp.-layer on the bottom electrode stabilize the underlaid layers.