• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.175-176
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• 2008

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, $[(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}(Nb_{0.96}Sb_{0.04})]O_3$ ceramics were fabricated using $Ag_2O$ as sintering aid and a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $SrTiO_3$ substitution. $SrTiO_3$ substitution enhanced density, dielectric constant$(\varepsilon_r)$ and electromechanical coupling factor$(k_p)$. However, mechanical quality factor was deteriorated. At the 0.5mol% $SrTiO_3$ substitution, density, electromechanical coupling factor$(k_p)$, dielectric constant$(\varepsilon_r)$ and piezoelectric constant$(d_{33})$ of specimen showed the optimum value of 4.437g/$cm^3$, 0.457, 1294, 265pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.30-30
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• 2008

Lead-free piezoelectric ceramics 0.97$(Na_{0.5}K_{0.5})NbO_3$-0.03Ba$(Ti_{1-x}Sn_x)O_3$ [NKN-BTS-x] ceramics doped with 1 mol% $MnO_2$ have been fabricated by a sintering technique with muffling. The $MnO_2$-doped NKN-BTS-x ceramics with x$\leq$0.2 have pure orthorhombic perovskite structure at room temperature. The dense microstructure was developed with grain growth as an increase of amount of Sn. Moreover, the addition of Sn was found to have a significant influence on piezoelectric properties. In particular, the $MnO_2$-doped NKN-BTS-0.1 ceramics showed improved piezoelectric properties of piezoelectric constant ($d_{33}$=145pC/N), relatively large electromechanical coupling factor ($k_p$=43%), dielectic constant (${\varepsilon}^T_{33}/{\varepsilon}_0$=676) dielectric loss (tan$\delta$=1.3%).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.651-655
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• 2013

$(Ba_{0.85}Ca_{0.15})(Ti_{0.9}Zr_{0.1})O_3$ + 0.04 wt% $CeO_2$ lead-free ceramics were synthesized by conventional sintering process and the effect of calcination temperature on microstructure, dielectric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at $1,125^{\circ}C$ calcination temperature which show the optimal electrical properties, $k_p$~0.457, $d_{33}$~367 pC/N, $Q_m$~158 and $T_c$~$85^{\circ}C$. These results show that the piezoelectric properties can be improved by appropriate calcination temperature.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.218-220
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• 2006

Sn-3.0Ag-0.5Cu solder is widely used as micro-joining materials of flip chip package(FCP) because of the fact that it causes less dissolution and has good thermal fatigue property. However, compared with ternary electroplating in the manufacturing process, binary electroplating is still used in industrial field because of easy to make plating solution and composition control. The objective of this research is to fabricate Sn-3.0Ag-0.5Cu solder bumping having accurate composition. The ternary Sn-3.0Ag-0.5Cu solder bumping could be made on a Cu pad by sequent binary electroplating of Sn-Cu and Sn-Ag. Composition of the solder was estimated by EDS and ICP-OES. The thickness of the bump was measured using SEM and the microstructure of intermetallic-compounds(IMCs) was observed by SEM and EDS. From the results, contents of Ag and CU found to be at $2.7{\pm}0.3wt%\;and\;0.4{\pm}0.1wt%$, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.33-41
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• 2010

Crack propagation mechanisms of Sn-3.0Ag-0.5Cu solder were studied in strain controlled push-pull creepfatigue conditions using the fast-fast (pp) and the slow-fast (cp) strain waveforms at 313 K. Transgranular cracking was found in the pp strain waveform which led to the cycle-dominant crack propagation and intergranular cracking in the cp strain waveform that led to the time-dominant crack propagation. The time-dominant crack propagation rate was faster than the cycle-dominant crack propagation rate when compared with J-integral range which resulted from the creep damage at the crack tip in the cp strain waveform. Clear recrystallization around the crack was found in the pp and the cp strain waveforms, but the recrystallized grain size in the cp strain waveform was smaller than that in the pp strain waveform. The cycle-dominant crack propagated in the normal direction to the specimen axis macroscopically, but the time-dominant crack propagated in the shear direction which was discussed in relation with shear micro cracks formed at the crack tip.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.435-438
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• 2012

As lead-free piezoelectric materials, $Ag_2O$ doped $0.95(K_{0.5}Na_{0.5})NbO_3-0.05LiNbO_3+x$ mol% (where x = 0, 0.5, 1, 1.5, 2, 2.5 and 3, respectively) ceramics were fabricated by a conventional sintering process. The doping effects on the microstructure and electrical properties of the $0.95(K_{0.5}Na_{0.5})NbO_3-0.05LiNbO_3$ ceramics were systematically investigated. When the 3 mol % $Ag_2O$ doped $0.95(K_{0.5}Na_{0.5})NbO_3-0.05LiNbO_3$ samples were sintered at $1,080^{\circ}C$ for 5 hrs in air, these ceramics showed excellent values of density=4.20 $g/cm^3$, piezoelectric constant ($d_{33}$)=174 pC/N and phase transition temperature$(T_c)=421.6^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.205-209
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• 2009

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)$NaNbO_{3-x}BaTiO_3-0,09LiNbO_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $BaTiO_3$ substitution. All the specimens showed orthorhombic phase structure without secondary phase, $BaTiO_3$ substitution enhanced density, dielectric constant(${\epsilon}_r$) and electromechanical coupling factor($k_p$), However, mechanical quality factor was deteriorated. Curie temperature of specimens was observed as about $380^{\circ}C$. At the $BaTiO_3$ substitution of 4 mol%, density, electromechanical coupling factor($k_p$), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.493g/cm^3$, 0.236, 175, 70 pC/N, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.22-26
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• 2014

$(Ba_{0.85}Ca_{0.15})(Ti_{0.9}Zr_{0.1})O_3$ + 0.04 wt% $CeO_2$ lead-free ceramics were prepared by conventional oxide-mixed method and the effect of sintering temperature on microstructure, dielectric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at $1,400^{\circ}C$ sintering temperature which show the optimal electrical properties, $k_p{\sim}0.412$, $d_{33}{\sim}316pC/N$, $Q_m{\sim}144$, ${\varepsilon}_r{\sim}3,345$ and $T_c{\sim}85^{\circ}C$. These results show that the sintering temperature plays an important role in piezoelectric properties.

• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.1-6
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• 2017

A comparative study of microwave and conventional sintering of lead-free $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-BaZrO_3-CuO$ ceramics is presented. It was found that microwave sintering (MWS) can be successfully applied to the fabrication of large strain Bi-perovskite with electric field-induced strains comparable to those obtained with conventional sintering (CFS). Although MWS resulted in smaller grained microstructures than CFS, the ferroelectric properties were stronger in MWS-derived specimens than in the CFS-derived ones. The piezoelectric strain constant $d_{33}{^*}$ of the CFS-derived specimens reached a maximum value of 372 pm/V after sintering at $1100^{\circ}C$, whereas that of MWS-derived specimens peaked at $950^{\circ}C$ with a $d_{33}{^*}$ value of 324 pm/V.

• Korean journal of food and cookery science
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• v.29 no.5
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• pp.605-616
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• 2013

A multistage approach for service recovery enables restaurant managers to do the most effective recovery strategies to reduce customer dissatisfaction and lead to positive behavioral intentions. The purpose of this study was to identify the most effective service recovery strategies in terms of service stage and examine the relationship between service strategies and behavioral intentions. A total of 227 diners examined the customer perceptions to recovery strategies (tangible strategy and intangible strategy) following service failures in each of the four stages:1) reservation and parking, 2) seating and ordering, 3) meal consumption, and 4) payment and exit. The one-way ANOVA showed that intangible strategies were relatively more effective than tangible strategies regardless of service stages. Free meal or free dessert were most effective in service stage 1 and stage 2 whereas correct the failure and reperformance of service found to be the most effective service recovery strategy. Regarding the association between service recovery strategies and behavioral intentions, multiple regression analysis showed that intangible strategies influenced diners' likelihood of positive behavioral intentions whereas tangible strategies lead to diners' willingness to positive behavioral intentions only in service stage 1. The findings enable restaurant practitioners to improve service recovery activities from a service stage perspective.