• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.83-88
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• 1995

The common practice for the identification of piezoelectric properties is based on the use of immittance of a resonator with a certain geometry and poling direction. In this paper, a new method is suggested to identify the complex-valued piezoelectric material constants. This method Is based on the minimization of differences between the analytical immittance and the experimental measurement of resonator. Non-linear minimization problems are formulated to find out the unknown properties relevant to the resonators. The immittance data used for identification are measured at a number of frequencies which cover the vicinity of resonance frequency and the low frequency region. To illustrate the proposed technique, the complex-valued coefficients are identified for a typical PZT4 ceramic composition.

• Journal of Biosystems Engineering
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• v.34 no.4
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• pp.260-268
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• 2009

As a basic study to develop a high sensitive biosensor using film bulk acoustic resonator, the mathematical model for analyzing the resonance characteristics of bulk acoustic resonator with acoustic Bragg reflectors was investigated. The simulation results due to the number of acoustic Bragg reflectors with low and high acoustic impedance materials were compared with the experimental results for 1, 2.25 and 5 MHz of PZT based bulk acoustic resonators with various acoustic Bragg reflectors. At the fabricated bulk acoustic resonator with an odd number of acoustic Bragg reflectors, low and high acoustic impedance materials in sequence under the bottom electrode showed better resonance characteristics than even number of acoustic Bragg reflectors. The changes of resonance frequencies due to the increase of number of acoustic Bragg reflectors by simulation and experiment, respectively showed approximately similar tendency but some differences in input impedance between the experiment and simulation were found. The derived mathematical model for describing the resonance characteristics of the bulk acoustic resonator with acoustic Bragg reflector will be available for analyzing the design parameters for development of biosensor using bulk acoustic resonator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.43-49
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• 2005

Temperature stabilities of resonance frequencies of the substrates are very important in piezoelectric ceramics oscillators and fitters. In this study, it was investigated thermal resisting property of the length-extensional vibration mode of PZT ceramics. The mode can be utilized in fabricating ultra-small 55 kHz IF devices. We fabricated the ceramic specimens with x = 0.51, 0.52, 0.53, 0.54, and 0.55 in the Pb(Zr$\sub$x/Ti$\sub$1-x/)O$_3$ system. And their resonance frequencies were measured before 1st thermal aging, after 1st and 2nd thermal aging. In order to investigate the influence of thermal aging on thermal resisting properties, thermally aged specimens were once mote thermally aged. Before 1st thermal aging, the specimens of the compositions with morphotropic phase, x = 0.53 and rhombohedral phase, x = 0.54 have weak thermal resisting property of resonance frequency, while tetragonal phase, x = 0.51 has robust thermal resisting property of resonance frequency. 1st thermal aging improved thermal resisting property of resonance frequency in all specimens.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.298-305
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• 1996

The common practice for the identification of piezoelectric properties is based on the use of immittance behavior of a resonator with a certain geometry and poling direction. In this paper, a new method is suggested to identify the complex-valued piezoelectric material constants. This method is based on the minimization of differences between the analytical immittance and the experimental measurement of resonator. Non-linear minimization problems are formulated to find out the unknown properties relevant to the resonators. The immittance data used for identification are measured at a number of frequencies which cover the vicinity of resonance frequency and the low frequency region. To illustrate the proposed technique, the complex-valued coefficients are identified for a typical PZT4 ceramic composition.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2568-2571
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• 2002

A LCD backlight inverter control IC based on the piezoelectric transformer (PZT) for Cold Cathode Fluorescent Lamp (CCFL) lighting is proposed. It is indeed a variable frequency, variable duty (VFVD) controller having dual feedback control loops for achieving both the regulation of lamp current and the maximum efficiency. The PWM controller regulates the lamp current, while the PLL controller tunes the operating frequency to the frequency that the efficiency of the combined LC-PZT resonator becomes maximum. The mixed PLL/PWM control technique lets the backlight inverter operate at the maximum efficiency in spite of the variation of component and environment. The controller features include a protection for an open or broken lamps, and an open lamp regulation.

• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.98-102
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• 2015

The radiative quantum efficiency of a solid-state laser was measured by photoacoustic spectroscopy with a PZT as the detector. The radiative quantum efficiency was about 58.3 % for a laser-diode pumped Nd:S-VAP laser under lasing conditions. The measurement of radiative quantum efficiency was presented as an effective method for the optimization of a laser resonator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.352-353
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• 2005

In this paper, an ultrasonic level limit sensor with a new structure utilizing the acoustic impedance matching is proposed to be able to check it out a change of water-level. 2 PZT resonators with the same property are bonded directly on the polyethylene plate. One is for transmitter as an ultrasonic transducer, the other one is for receiver. In this case, a polyethylene plate will operate as an acoustic guider to transmit a transverse wave between 2 PZT resonators in air. While in the water, a polyethylene plate having a similar acoustic impedance with the water will be emitted an acoustic energy into the water as a longitudinal wave. According to this mechanism, there was a wide difference of acoustic signal output between underwater and in air. As a summary, it is believed that this proposed level limit sensor could be used as a new one with strong toughness from the external electrical and mechanical noise.

• 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 KIEE Conference
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• 2005.07c
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• pp.1870-1872
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• 2005

In this study, an ultrasonic level limit sensor with a new structure utilizing the acoustic impedance matching is proposed to be able to check it out a change of water-level. 2 PZT resonators with the same property are bonded directly on the polyethylene plate. One resonator is for transmitter as an ultrasonic transducer, the other one is for receiver. In this case, a polyethylene plate will operate as an acoustic guider to transmit a transverse wave between 2 PZT resonators in air. While in the water, a polyethylene plate having a similar acoustic impedance with the water will be emitted an acoustic energy into the water as a longitudinal wave. According to this mechanism, there was a wide difference of acoustic signal output between underwater and in air. As a summary, this proposed level limit sensor could be used as a strong candidate with low cost and more stable one.

• 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.