• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.483-488
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• 2016

Ultrasound imaging by using piezoelectric materials, such as lead zirconium titanate (PZT) has been one of the most preferred modes of imaging in the medical field due to its simple, low cost and non-ionizing radiation in comparison to other imaging techniques. Recently, the market demand for portable ultrasound is becoming larger with applications in developing countries, disaster area, military, and emergency purposes. However, most of ultrasound probes used is bulky and high power consumable, so unsuitable for such applications. In this study, the 3 layered ceramic specimen consisted of 128 pitches of $420{\mu}m$ in width and $450{\mu}m$ in thickness were prepared by using the Ti-rich PZT compositions co-fired at $1,050^{\circ}C$. Their electrical and ultrasound pulse-echo properties were investigated and compared to the single layer specimen. The 3 layered ultrasound probe showed 1.584 V of Vp-p, which is 3.2 times higher than single layered one, implying that it would allow effectively such a portable ultrasound probe system. The result were discussed in terms of higher capacitance, lower impedance and higher dielectric coefficient of the 3 layered ultrasound probe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.48-48
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• 2008

현재 압전재료로써 사용되고 있는 PZT계 세라믹스는 우수한 압전 및 유전특성으로 초음파 센서, 압전변압기, 액츄에이터, 필터, 레조네이터와 같은 여러 응용분야에 널리 사용되어지고 있다. 그러나 납을 60%이상 포함하므로 환경오염에 의하여 그 사용에 대한 규제가 강화되고 있어 최근에는 납을 함유하지 않은 무연 환경친화형 압전세라믹스가 주목받고 있다. 현재 무연 조성 세라믹스에는 텅스텐-브론즈 형, 비스머스 레이어형, 페로브스카이트 형 등이 이으며, 그 중 페로보스카이트 혈을 제외하고는 보통 소성법 조제시 낮은 압전특성을 갖는다. 그러므로 압전특성을 증가시키기 위하여 Hot pressing, Hot forging, RTGG(Reactive Template Grain Growth), SPS(Spark Plasma Sintering), 그러나 이는 무연 세라믹스의 대량생산 과정에서 어려운 문제를 가지고 있고, 저가격 관점에서 볼 때 보통소성법이 보다 바람직하다. 그래서 보통소성법으로 NKN세라믹스의 소결성을 향상 시키고 비교적 높은 압전특성을 얻기 위해서 $LiSbO_3$, $LiNbO_3$, $LiTaO_3$, alkaline-earth(Mg, Ca, Sr, Ba) 등을 첨가한 논문들이 보고되고 있으며, 이러한 재료들의 kp는 대략 0.3-0.4를 나타내고 있다. 따라서, 본 연구에서는 소결온도를 낮추고자 $Ag_2O$를 소결조제로 사용하였고 유전 및 압전특성을 높이고자 소결시간 변화시켜 시편을 제작하여 NKN 세라믹스의 유전 및 압전특성을 조사하였다.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.527-532
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• 2014

$0.97Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3-0.03LaFeO_3$ lead-free piezoelectric ceramics were fabricated by a solid state reaction method. $LaFeO_3$ additives were added to $Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ for volatile compensation of bismuth and sodium ions in the sintering process. To create A-site vacancies, the mole ratio and charge valence of A-site ions ($Bi^{3+}$, $Na^+$ and $K^+$) were controlled. The improved piezoelectric properties were observed by addition of $LaFeO_3$ and control of A-site vacancies. In particular, a $d_{33}^*(S_{max}/E_{max})$ value of 614pm/V and an electric field induced strain of 0.33% was observed in $0.97Bi_{0.505}(Na_{0.78}K_{0.22})_{0.485}TiO_3-0.03LaFeO_3$ ceramic.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.858-868
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• 1992

0.085Ba(LaS11/2TNbS11/2T)OS13T-0.915Pb(ZrS1yTTiS11-yT)OS13T (0.45$\leq$y$\leq$0.65) transparent electrooptic ceramics were fabricated by two-stage sintering method. The structural, ferroelectric and electrooptic properties were investigated varying composition and second sintering time. Also the possibility of application to electrooptic device was studied. If we increase the PbZrOS13T contents, dielectric constants were increased and Curie temperature was decreased. In the composition of 0.55[mol] PbZrOS13T, electromechanical coupling factor and piezoelectric charge constant were the highest values of 43[%] and 173x10S0-12T[C/N], respectively. Mechanical quality factors were decreased with the increasing PbZrOS13T contents. Light transmittance was increased with wavelength when measured from 300[nm] to 900[nm], and with PbZrOS13T contents in the range of 0.50[mol]-0.65[mol], and had the highest value of 67[%] in the composition of 0.65[mol] PbZrOS13T. From the results of ferroelectric hysteresis loop and transmitted light intensity with electric field, the specimens with compositions of 0.65,0.60,0.55[mol] PbZrOS13T were applicable to electrooptic memory device and those with compositions of 0.50,0.45[mol] PbZrOS13T were applicable to linear electrooptic device.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.683-689
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• 2005

The structural, piezoelectric and ferroelectric properties of $(1-x)(Bi_{0.5}Na_{0.5})TiO_3$ x=0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ceramics were investigated. A gradual change in the crystal and microstructures with tile increase of $BaTiO_3$ (BT) concentration was observed. The $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) samples show unusual properties as ferroelectric relaxer materials. We observed a phase transition in BNT solid solutions with BT having normal ferroelectric phase transition. At room temperature, BNT presents a single phase without the morphotropic phase boundary (MPB). In the case of samples doped with $4\~8 mol\%$ BT, rhombohedral-tetragonal MPB was formed and the piezoelectric properties were improved.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.325-331
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• 1999

SrWO4가 첨가된 (Sr1-xBax)(Mg1/3Nb2/3)O3의 마이크로파 유전특성에 관하여 조사하였다. 관찰된 조성영역에서 Sr(Mg1/3Nb2/3)O3과 Ba(Mg1/3Nb2/3)O3은 (Sr1-xBax)(Mg1/3Nb2/3)O3고용체를 형성하고 SrWO4의 첨가는 고용체의 소결성을 향상시켜 소결온도 155$0^{\circ}C$에서 상대밀도 97% 이상을 얻었다. 소결한 시편의 EDS분석결과, SrWO4의 첨가량이 많은 시편에서 2차상이 존재하는 것을 알수 있었다. 순수한 Sr(Mg1/3Nb2/3)O3에 SrWO4를 0.01 mole첨가하여 1550~1$600^{\circ}C$에서 소결한 시편의 유전특성은 $\varepsilon$r 30, Q$\times$fo$\geq$55000,$ au$f -23 ppm/$^{\circ}C$이었다. 0.01 mole SrWO4가 첨가된 (Sr1-xBax)(Mg1/3Nb2/3)O3 고용체의 유전율과 온도계숙가 x에 따라 점차적으로 계속 증가하였고 Q$\times$fo는 x$\leq$0.25에서 x에 따라 감소하고 x$\geq$0.3에서 다시 증가하였다. (Sr0.65Ba0.35)(Mg1/3Nb2/3)O3+0.01SrWO4의 조성을 갖는 시편에서 $\varepsilon$r 34.4, Q$\times$fo$\geq$55000,$\tau$f 0 ppm/$^{\circ}C$이었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.955-961
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• 2011

We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, $Ba(Zn_{1/3}Ta_{2/3})O_3$ 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 $ZrO_2$ doped $Ba(Zn_{1/3}Ta_{2/3})O_3$ 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.99-99
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• 2009

Two different micro-flows during the evaporation of ink droplets were achieved by engineering both surface tension gradient and compositional gradient across the ink droplet: (1) Coffee-ring generating flow resulting from the outward flow inside the ink droplet & (2) Marangoni flow leading to the circulation flow inside the ink droplet. The surface tension gradient and the compositional gradient in the ink droplets were tailored by mixing two different solvents with difference surface tension and boiling point. In order to create the coffee-ring generating flow (outward flow), a single-solvent system using N,N-dimethylformamide with nano-sized spherical alumina particles was formulated, Marangoni flow (circulation flow) was created in the ink droplets by combining N,N-dimethylformamide and fotmamide with the spherical alumina powders as a co-solvent ink system. We have investigated the effect of these two different flows on the formation of ceramic films by inkjet printing method, The packing density of the ceramic films printed with two different ink systems (single- and co-solvent systems) and their surface roughness were characterized. The dielectric properties of these inkjet-printed ceramic films such as dielectric constant and dissipation factor were also studied in order to evaluate the feasibility of their application to the electronic ceramic package substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.192-192
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• 2009

We have successfully demonstrated the inkjet printing process to fabricate $Al_2O_3$ thick films without a high temperature sintering process. A single solvent system had a coffee ring pattern after printing of $Al_2O_3$ dot, line and area. In order to fabricate the smooth surface of $Al_2O_3$ thick film, we have introduced a co-solvent system which has nano-sized $Al_2O_3$ powders in the mixture of Ethylene glycol monomethyl ester and Di propylene glycol methyl ether. This co-solvent system approached a uniform and dense deposition of $Al_2O_3$ powders on the substrate. The packing density of inkjet-printed $Al_2O_3$ films is more than 70% which is very high compared to the value obtained from the films synthesized by other conventional methods such as casting processes. The characterization of the inkjet-printed $Al_2O_3$ films has been implemented to investigate its thickness and roughness. Also the dielectric loss of the films has been measured to understand the feasibility of its application to 3D integration package substrate.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.7
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• pp.26-31
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• 2005

In this paper, a small BPF(band pass filter) is designed using new probe type for wireless communication system. The dielectric resonator is used high Q ceramics for low loss characteristic. In order to provide a band pass filter which can be reduced in dimension, can be reduced in height, and can be surface-mounted. The filter was fabricated using $TE_{01{\delta}}$ mode dielectric resonator. The input/output probes are attached to coner portion of the rectangular metal cavity. Results of the manufactured filter($12{\times}12{\times}8[mm]$) show that the center frequency is 9.95358[GHz], the insertion loss is -1.9[dB], the 3[dB]_bandwidth is 14.9[MHz], and the loaf Q is 664.