• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.492-496
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• 2004

In this study, (0.96 －x)(PSN-PZT)－xBF－0.04 PNW＋0.3wt%MnO$_2$＋0.6wt%CuO ceramics were fabricated with the variations of the amount of BiFeO$_3$substitution and sintering temperature for the development of modified ceramics which can be sintered in the low temperature($\leq$100$0^{\circ}C$ ), and their microstructural, dielectric and piezoelectric characteristics were investigated. As the amount of BiFeO$_3$ substitution was increased, the density, mechanical quality factor(Q$_{m}$) and electromechanical coupling factor(k$_{p}$) showed the maximum value at each of sintering temperature. At sintering temperature of 98$0^{\circ}C$ and BiFeO$_3$substitution of 2 mol%, the density, dielectric constant and electromechanical coupling factor(k$_{p}$) showed the maximum value of 7.84 g/㎤, 1415 and 0.49, respectively. And at sintering temperature of 95$0^{\circ}C$ and BiFeO$_3$substitution of 3mol%, mechanical quality factor showed the maximum value of 1062. 1062.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.356-361
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• 2001

The structureal, dielectric and piezoelectric properties of Pb[(Sb$\_$1/2/Nb$\_$1/2/)$\_$x/-(Ni$\_$1/3/Nb$\_$2/3/)$\_$0.15-x/-(Zr$\_$y/Ti$\_$1-y/)$\_$0.85/]O$_3$(x=0∼0.05, y=0.47∼0.52) ceramics were investigated with the substitution of Pb(Sb$\_$1/2/Nb$\_$1/2/)O$_3$(abbreviated PSN) and the Zr/Ti ratio. At Zr/Ti ratio of 50/50, tetragonality was decreased and grain size abruptly decreased with the increase of PSN substitution. Curie temperature was decreased and dielectric constant increased with the substitution of PSN. The coercive field increased and remnant polarization decreased with the substitution of PSN. Electromechanical coupling factor(k$\_$p/) showed the highest value of 0.622 at 1mol% PSN, but mechanical quality factor(Q$\_$m/) showed the minimum value at that composition. Dielectric constant and electromechanical coupling factor with the Zr/Ti ratio showed maximum values at Zr/Ti ratio of 50/50 and mechanical quality factor showed minimum values near the Zr/Ti ratio of 50/50.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.462-466
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• 2007

Aluminum nitride (AlN) thin films were deposited on Si substrates by using polycrystalline (poly) 3C-SiC buffer layers, in which the AlN film was grown by pulsed reactive magnetron sputtering. Characteristics of grown AlN films were investigated experimentally by means of FE-SEM, X-ray diffraction, and FT-IR, respectively. The columnar structure of AlN thin films was observed by FE-SEM. X-ray diffraction pattern proved that the grown AlN film on 3C-SiC layers had highly (002) orientation with low value of FWHM (${\Theta}=1.3^{\circ}$) in the rocking curve around (002) reflections. These results were shown that almost free residual stress existed in the grown AlN film on 3C-SiC buffer layers from the infrared absorbance spectrum. Therefore, the presented results showed that AlN thin films grown on 3C-SiC buffer layers can be used for various piezoelectric fields and M/NEMS applications.

• Composites Research
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• v.12 no.2
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• pp.1-9
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• 1999

The piezoelectric material connected to external electric networks possesses frequency dependent stiffness and loss factor which are also affected by the shunting circuit. The external electric networks are generally specialized for two shunting circuits: one is the case of a resistor alone and the other is the combination of a resistor and an inductor. For resistive shunting, the material properties exhibit frequency dependency similar to viscoelastic materials, but are much stiffer and more independent of temperature. Shunting with a resistor and inductor introduces an electrical resonance, which can change the characteristics of structural resonance optimally in a manner analogous to a PMD (proof mass damper). Passive damping enhancement of composite beam using piezoelectric material connected to external electrical networks is achieved and presented in this paper.

• Steel and Composite Structures
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• v.23 no.6
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.33.2-33.2
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• 2009

Dielectric and piezoelectric properties of Lead-free $(1-x)(Bi_{0.5}K_{0.5})TiO_3-xBiFeO_3$ceramics prepared by a conventional solid state reaction method were investigated in the range of x = 0~10 mol%. Piezoelectric coefficient was increased from 31 pC/N at x = 0 mol% to 64 pC/N at x = 6 mol% then decreased with increasing x. Electromechanical coupling factor ($K_p$) was increased up to 0.18 at x = 10 mol%. On the other hand, mechanical quality factor ($Q_m$) was decreased. Grain size was not much changed with various x and a single perovskite with tetragonal symmetry was maintained at all compositions forming a solid solution between $(Bi_{0.5}K_{0.5})TiO_3$ and $BiFeO_3$. Depolarization temperature ($T_d$) was gradually decreased with increasing x from $302^{\circ}C$ at x = 0 to $245^{\circ}C$ at x = 10 mol%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.300-303
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• 2003

[ $0.91(PSN-PZT)-0.05BF-0.04PNW+0.3wt%MnO_2+0.6wt%CuO+xwt%CeO_2$ ] ceramics were fabricated with the variations of $CeO_2$ addition at the sintering temperature of $950^{\circ}C$ and their microstructure and dielectric and piezoelectric characteristics were investigated. As the amount of $CeO_2$ addition increased, the grain size, density and electromechanical coupling factor(kp) were increased and the mechanical quality factor(Qm) was decreased. At the $0.3wt%CeO_2$, density, grain size and electromechanical factor(kp) showed the maximum value of $7.87g/cm^3$, $3.22{\mu}m$ and 0.5, respectively. However, mechanical quality factor(Qm) showed the minimum value of 807 at the $0.5wt%CeO_2$.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.813-817
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• 2002

Magnetoelectric(ME) laminate composites of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3 (PMN-PT)$ and Terfenol-D were prepared by sandwiching single crystals of PMN-PT between Terfenol-D disks. The magnetoelectric voltage coefficient (dE/dH) of the composite was determined to be 10.30 V/cm${\cdot}$Oe, at 1 kHz and under a dc magnetic bias of 0.4 T. The value of dE/dH is ∼80 times higher than either that of naturally occurring magnetoelectrics or artificially-grown magnetoelectric composites. This superior magnetoelectric voltage coefficient is attributed to the high piezoelectric voltage constant as well as the high elastic compliance of PMN-PT single crystal and the large magnetostrictive response of Terfenol-D.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.188-191
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• 2000

The properties of piezoelectric and dielectric for 0.05Pb(Mn$\_$0.4/W$\_$0.2/Nb$\_$0.4/)O$_3$ - 0.95PbZr$\_$x/Ti$\_$1-x/O$_3$ compositions have been investigated. In the composition of 0.05Pb(Mn$\_$0.4/W$\_$0.2/Nb$\_$0.4/)O$_3$ - 0.95PbZr$\_$0.51/Ti$\_$0.49/O$_3$, the values of k$\_$p/ and $\varepsilon$$\_$33/$\^$T// $\varepsilon$$\_$0/ are maximized, but Q$\_$m/ was minimized (k$\_$p/=56.5[%], Q$\_$m/=1130, d$\_$33/=258[pC/N], $\varepsilon$$\_$33/$\^$T// $\varepsilon$$\_$0/=1170). The grain size was suppressed and the uniformity of grain was improved at the 1100[˚C]. Also, we can see the dielectric constants variations between the before poling and after poling. This effect results from the effect(increase element of dielectric constants) between dipole switching and electrostriction inducing stress and dipole direction to the poling orientation(decrease element of dielectric constants). At x=0.51, we can find MPB(morphotropic phase boundary).

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.558-561
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• 1996

PZT powders were prepared by the molten salt synthesis method. The porous PZT ceramics were made from a mixture of PZT and polyvinylalcohol(PVA) by BURPS(Burnout Plastic Sphere) technique. The porous PZT bodies were fabricated from the green compacts with various amounts of PVA spheres. The piezoelectric coefficient d$_{33}$ (334~350*10$^{-12}$ C/N)of porous PZT ceramics(364*10$^{-12}$ C/N). The figure of merit(d$_{h}$g$_{h}$) of porous PZT specimens evaluating the sensitivity for ultrasonic transducer applications was improved significantly(11~70times) in comparison with that of single phase PZT ceramics(100*10$^{-15}$ m$^{2}$/N). The thickness mode coupling factor k$_{t}$(0.5~0.6) of porous specimens was comparable with that of single phase PZT ceramics(k$_{t}$=0.7). The mechanical quality factor of porous PZT specimens was smaller than 10, and thus these porous PZT ceramics would be believed as a good candidate for broad band hydrophone applications. (author). 10 refs., 7 figs.igs.igs.