• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.42-45
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• 2002

Properties of lead zirconate titanate ferroelectric thin films prepared by rapid thermal annealing/direct insertion thermal annealing were investigated. The remnant polarization (Pr), saturation polarization (Ps), and coercive force (Ec) of typical samples annealed by rapid thermal annealing (RTA) are about 13.7 $\mu$ C/cm$^2$, 27.1 $\mu$C/cm$^2$, and 55.6 kV/cm, respectively. The dielectric constant of the sample is about 786, the dielectric loss tangent is about 2.4% at 1 kHz. Furthermore, ferroelectric, conduction, and piezoelectric properties of the thin films annealed by RTA process and the direct insertion thermal annealing (DITA) process were compared. The influence of temperature in the dry process on the above properties was also investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.350-351
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• 2006

Thick film mechanical sensors can be categorized into four main areas piezoresistive, piezoelectric, capacitive and mechanic tube. In this areas, the thick film strain gage is the earliest example of a primary sensing element based on the substrates. The latest thick film sensor is used various pastes that have been specifically developed for pressure sensor application. Some elastic materials exhibit a change in bulk resistivity when they are subjected to displacement by an applied pressure. This property is referred to as piezoresistivity and is a major factor influencing the sensitivity of a piezoresistive strain gage. The effect of thick film resistors was first noticed in the early 1970, as described by Holmes in his paper in 1973.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.373-378
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• 2016

Recent researches have reported that the superposition of ultrasonic vibrations in metal forming provides beneficial effects such as the reduction of forming load, flow stress and interfacial friction which improves the surface quality of end products. This paper presents experimental investigations on the effects of ultrasonic vibrations in upsetting tests of aluminum. The ultrasonic exciting system consists of piezoelectric transducer and resonator was designed and constructed to superimpose high frequency oscillation on the forming tools. Ultrasonic vibration-assisted upsetting tests were performed for three vibration modes five amplitudes, and the results were compared with those of conventional upsetting tests. The results showed that the superimposition of ultrasonic vibration reduces the upsetting load, and the load reduction is only dependent on the amplitude of the applied vibration regardless of deformation histories and vibration modes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.699-705
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• 2013

This paper presents vibration testing, control, and finite element analysis of a piping system, which is subjected to the changes in fluid levels. Nuclear power plants typically employ a cooling system that uses sea water. These systems are subjected to dynamic characteristic changes caused by sea-level variations, which introduces failures of cooling system components. Therefore in this study, analytical and experimental studies were performed to understand the effect of sea-level changes on the dynamic characteristics of piping systems. It was shown that, as the sea-level increases, pipe's natural frequencies decreases in relation to its mode shape. A 1/14 scale model was also built to compare the results obtained by the analytical study. A good agreement between experiment and analytical studies were observed. Finally, an on-line resonant frequency identification system was proposed and developed, which utilizes piezoelectric transducers as sensors and actuators, in order to avoid catastrophic failure of piping systems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.667-673
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• 2000

A number of issues related with the vibrational behavior of pretwisted rotating beams featuring anisotropic properties and incorporating adaptive capabilities are considered in this paper. The adaptive capabilities are provided by a system of piezoactuators bonded or embedded into the structure. Based on the converse piezoelectric effect and on the out of phase activation, boundary control moments are pizoelectrically induced at the beam tip. A feedback control law relating the induced bending moments with the kinematical response quantities appropriately selected is used, and its beneficial effects, considered in conjunction with that of the beam anisotropy and structural pretwist upon the eigenvibration characteristics are highlighted

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.29-37
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• 2022

The present paper deals with the application of one dimensional piezoelectric materials in particular piezo-thermoelastic nanobeam. The generalized piezo-thermo-elastic theory with two temperature and Euler Bernoulli theory with small scale effects using nonlocal Eringen's theory have been used to form the mathematical model. The ends of nanobeam are considered to be simply supported and at a constant temperature. The mathematical model so formed is solved to obtain the non-dimensional expressions for lateral deflection, electric potential, thermal moment, thermoelastic damping and frequency shift. Effect of frequency and nonlocal parameter on the lateral deflection, electric potential, thermal moment with generalized piezothermoelastic theory are represented graphically using the MATLAB software. Comparisons are made with the different theories of thermoelasticity.

• Journal of Mechanical Science and Technology
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• v.20 no.1
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• pp.76-84
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• 2006

Arrayed ultrasonic sensors based on the piezoelectric thin film (lead-zirconate-titanate: Pb($Zr_{0.52}Ti_{0.48})O_{3}$) having composite membrane structure are fabricated. Different thermal and elastic characteristics of each layer generate the residual stress during the high temperature deposition processes, accomplished diaphragm is consequently bowing. We present the membrane deflection effects originated from the residual stress on the resonant frequencies of the sensor chips. The resonant frequencies ($f_r$) measured of each sensor structures are located in the range of $87.6{\sim}111\;kHz$, these are larger $30{\sim}40\;kHz$ than the resultant frequencies of FEM. The primary factors of $f_r$ deviations from the ideal FEM results are the membrane deflections, and the influence of stiffness variations are not so large on that. Membrane deflections have the effect of total thickness increase which sensitively change the $f_r$ to the positive direction. Stress generations of the membrane are also numerically predicted for considering the effect of stiffness variations on the $f_r$.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1108-1114
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• 1999

Microstructure and electrical properties of ZnO-doped (0-5 mol%) 0.05 Pb(Mn1/3Sb2/3)O3-0.95 PZT ceramics were investigated. Sintering temperature was decreased to 100$0^{\circ}C$ due to eutetic reaction between PbO and ZnO. Grain-size increased up to adding 1mol% ZnO and then decreased. Compositions of grain and grain-boundary were investigated by WDS. Lattice parameter was decreased with ZnO addition. Density increased with ZnO addition and reached to the maximum of 7.84(g/cm2) at 2 mol% ZnO. The effect of ZnO on electrical properties of PMS-PZT was investigated. At 3mol% ZnO addition electromechanical coupling factor(kp) was about 50% and relative dielectric constant($\varepsilon$33/$\varepsilon$0) was 997 Mechanical quality factor(Qm) decreased with ZnO addition. Lattice parameters and tetragonality(c/a) were measured to investigate relationship between the electric properties and substitution of Zn2+. At 3 mol% ZnO tetragonality was maximiged at c/a=1.0035 Curie temperature (Tc) decreased slightly with ZnO addition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.915-920
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• 2007

AIN-based film bulk acoustic resonator (FBAR) devices which adopt a membrane-type configuration such as Mo/AIN/bottom-metal/Si are fabricated by employing a novel process. The proposed resonator structure does not require any supporting layer above the substrate, which leads to the reduction in energy loss of the resonators. For all the FBAR devices, the frequency response characteristics are measured and the device parameters, such as return loss and input impedance, are extracted from the frequency responses, and analyzed in terms of the various metals such as Al. Cu, Mo, W used in the bottom-electrode. The mass-loading effect caused by the used bottom-electrode metals is found to be the main reason for the difference revealed in the measured characteristics of the fabricated FBAH devices. The results obtained in this study also show that the degree of match in lattice constant and thermal expansion coefficient hetween piezoelectric layers and electrode metals is crucial to determine the device performance of FEAR.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.562-566
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• 2001

The effects of MnO$_2$ addition on the properties in Pb(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ relaxor ferroelectrics were studied in the phase transition temperature range from -4$0^{\circ}C$ to 11$0^{\circ}C$. Specimens were made via solid state processing method. Dielectric properties, piezoelctric properties, electric-field-induced strain were examined to clarify the effect of MnO$_2$ addition in 0.9MN-0.1PT. As the amount of MnO$_2$ increases, the maximum dielectric constant and the dielectric loss decreases. Q$_{m}$ increased by increasing the doping contents of Mn. When 0.5wt% MnO$_2$ was doped, Q$_{m}$ increased from 95 to 480. The electric-filed-induced strain and polarization decreases as the amount of MnO$_2$ increases. From the experimental results, it was suggested that Mn behaves as an ferroelectric domain pinning element.ent.