• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.35-39
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• 2006

In this study, in order to develop the multilayer piezoelectric actuator and ultrasonic resonator, PMN-PNN-PZT ceramics were fabricated by sintering with $Li_2CO_3-Na_2CO_3$ as sintering aids at $950^{\circ}C$ and their piezoelectric and dielectric characteristics were investigated as a function of PNN substitution. With increasing PNN substitution, dielectric constant(${\epsilon}_r$), electromechanical coupling factor(kp), and piezoelectric d constant($d_{33}$) were increased to $12 mol\%$ PNN substitution and then showed a tendency to decrease rapidly With increasing PNN substitution, crystal structure changed from tetragonal to rhombohedral at $12 mol\%$ PNN substitution and then secondary phase was appeared and its intensity was increased. At the $12 mol\%$ PNN substituted PMN-PZT composition ceramic sintered at $950^{\circ}C$, density, kp, $d_{33}$ and Qm showed the optimum value of $7.79 g/cm^3$, 0.599, 419 pC/N, and 894, respectively for multilayer piezoelectric actuator application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.203-204
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• 2008

In this study, in order to develop the multilayer piezoelectric actuator and ultrasonic resonator, PMN-PNN-PZT ceramics were fabricated by the variations of ball size at sintering temperature of $900^{\circ}C$ and their piezoelectric and dielectric characteristics were investigated as a function of the variations of ball size. When the ball size was 3mm$\phi$, density, dielectric constant$({\varepsilon}r)$, electromechanical coupling factor(kp) and piezoelectric d constant$(d_{33})$ were increased. At the ball size of 3mm$\phi$, the specimen showed the optimum values of density=7.909g/$cm^3$, kp=0.592, Qm=1292, $d_{33}$=368pC/N, $\varepsioln_r$=1502, respectively.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.73-77
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• 1998

Langasite(La3Ga5SiO14) is a new piezoelectric material which is similar to quartz, LN(LiNbO3) and LT(LiTaO3) in its acoustic behavior. In this study, pure Langasite and Langasite family groups were synthesized by the solid state reactions in air. For the synthesis process, diffusion species were investigated and sintered body of synthesized powders were studied on dielectric property according to surface microstructures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electro- mechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creak coupled symmetric and anti- symmetric vibration modes. Accordingly, the simulation for ceramic (inter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.885-887
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• 1999

The piezoelectric ceramic resonator using length extensional vibration rather than contour extensional vibration in terms of the size is suitable for personal portable communication. In this paper, $Pb(Zr_{x}Ti_{l-x})O_{3}$ + r[wt%]$Cr_{2}O_{3}$ ceramics, x=0.56, 0.53, 0.50 (ie, Zr/Ti ratios = 56 /44, 53/47, 50/50) r=0, 0.3[wt %], were fabricated. Temperature stability of length extensional vibration mode of those specimens was investigated. Both crystal structure with rhombohedral phase in the case of no addition of $Cr_{2}O_{3}$ and crystal structure with morphotrophic phase boundary in case of additions of 0.3[wt %]$Cr_{2}O_{3}$ had the vest temperature stability and improved temperature stability through thermal aging.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.1-7
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• 1997

SAW filter has been used in mobile communication device, bandpass filter and resonator for merits )f miniaturization and high reliability. Materials for substrate mainly used single crystal such as LiNbO$_{3}$, LiTaO$_{3}$, ZnO. In this study, it was attempted that LiNbO$_{3}$ was substituted for piezoelectric ceramics(PZT4, PZT5A and PZT8) which had simple fabrication process because fabrication of crystal is difficult and it's cost is high. SAW filters were fabricated by the photolithography on piezoelectric ceramics substrates in order to compare their characteristics with LiNbO$_{3}$'s. The experimental value of center frequency was compared with theoretical one. The average difference of center frequency was 3.7%. PZT8 showed the best bandwidth properties among them. It is considered that PZT8 has higher mechanical quality factor and propagation velocity than others.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.980-986
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• 2001

Bragg reflector type FBAR was fabricated on the Si(100) substrate. We measured a frequency response of the resonator at 5.2 GHz and analyzed it by numerical calculation considering actual acoustic losses of each layer in the structure. We fabricated nine layer Bragg reflector of W-SiO$_2$pairs using r.f. sputtering method and fabricated AlN piezoelectric and Al electrodes using pulsed dc sputtering. The return loss(S$_{11}$) of the fabricated Bragg reflector type FBAR was 12 dB at 5.38 GHz and the series resonance frequency(f$_{s}$) was 5.376 GHz and the parallel resonance frequency(f$_{p}$) was 5.3865 GHz. Effective electro-mechanical coupling constant (K$_{eff{^2}}$) and Quality factors(Q$_{s}$), the Figures of Merit of the resonator, were about 0.48% and 411, respectively. We extracted acoustic parameters of AlN piezoelectric and reflection coefficient of the Bragg reflector by numerical calculation. We could know that material acoustic impedance and wave velocity of AlN piezoelectric decreased for intrinsic value and the electromechanical coupling constant(K$_2$) value was very low owing to the poor quality of the AlN piezoelectric. Reflection coefficient of Bragg reflector was 0.99966 and reflection band was very wide from 2.5 to 9.5 GHz.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.393-397
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• 2003

To investigate the effect of AIN c-axis orientation on the resonance performance of film bulk acoustic wave resonators, solidly mounted resonators with crybtallographically different AIN piezoelectric films were prepared by changing only the bottom electrode surface conditions. As increasing the degree of c-axis texturing, the effective electromechanical coupling coefficient ($\kappa$$\_$eff/)$^2$ in resonators increased gradually. The least 4 degree of full width at half maximum in an AIN(002) rocking curve, which corresponds to $\kappa$$^2$$\_$eff/ of above 5%, was measured to be necessary for band pass filter applications in wireless communication system. The longitudinal acoustic wave velocity of AIN films varied with the degree of c-axis texturing. The velocity of highly c-axis textured AIN film was extracted to be about 10200 n/s by mathematical analysis using Matlab.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.42-47
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• 2006

In this paper, we prepared high-quality ZnO thin films for application of FBAR (Film Bulk Acoustic Resonator) by using pulse DC magnetron sputtering. To prevent the formation of low dielectric layers between metal and piezoelectric layer, Ru film of 30 nm thickness was used as a buffer layer. In addition we investigated the influence of annealing condition with various temperatures. As the annealing temperature increased, the crystalline orientation with the preference of (002) c-axis and resistance properties improved. The single resonator which was fabricated at $500^{\circ}C$ exhibited the resonance frequency and the return loss 0.99 GHz and 15 dB, respectively. This work demonstrates potential feasibility for the use of thin film Ru buffer layers and the optimization of annealing condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electromechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emhpasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creat coupled symmetric and antisymmetric vibration modes. Accordingly, the simulation for ceramic filter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.