• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.84-90
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• 2019

The varistor properties and stability against dc-accelerated stress of $V_2O_5-Mn_3O_4-Co_3O_4-Dy_2O_3-Nb_2O_5-Bi_2O_3$ (VMCDNB)-doped zinc oxide ceramics sintered at $850-925^{\circ}C$ were investigated. Increasing the sintering temperature increased the average grain size from 4.6 to 8.7 mm and decreased the density of the sintered pellet density from 5.54 to $5.42g/cm^3$. The breakdown field decreased from 5919 to 1465 V/cm because of the increase in the average grain size. Zinc oxide ceramics sintered at $875^{\circ}C$ showed the highest nonlinear coefficient (43.6) and the highest potential barrier height (0.96 eV). Zinc oxide ceramics sintered at $850^{\circ}C$ showed the highest stability: the variation rate of the breakdown field was -2.0% and the variation rate of the nonlinear coefficient was -23.3%, after application of the specified stress (applied voltage/temperature/time).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.264-264
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• 2007

$B_2Mg_{2/3}/Nb_{4/3}O_7\;(B_2MN)$ thin films and $Bi_{3/2}MgNb_{3/2}O_7\;(B_{1.5}MN)$ thin films were deposited as a function of various deposition temperatures on Pt/$TiO_2/SiO_2$/Si substrates by radio frequency magnetron sputtering system. Both of their thin films are shown to crystalline phase at $500^{\circ}C$, deposition temperature, using 100W RF power. The composition of them and structural micro properties are investigated by RBS spectrum and SEM, AFM. 200 nm-thick $B_2MN$ thin films were deposited at room temperature had capacitance density of $151nF/cm^2$ at 100kHz, dissipation factor of 0.003 and had capacitance density of $584nF/cm^2$ at 100kHz, dissipation factor of 0.0045 at $500^{\circ}C$ deposition temperature. Both of their dielectric constant deposited at room temperature and at $500^{\circ}C$ were each approximately 40 and 100.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.671-676
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• 2009

The $Sr_{0.7}Bi_{2.3}Nb_2O_9$(SBN) thin films are deposited on Pt-coated electrode(Pt/Ti/$SiO_2$/Si) using RF sputtering method at various deposition conditions. We investigated the effect of deposition condition on the surface morphology and dielectric properties of SBN thin films. The optimum of the rougness showed about 4.33 nm in 70/30 of Ar/$O_2$ ratio. The crystallinity and rougness of SBN thin films were increased with the increase of rf power. Also, Deposition rate of SBN thin films was about 4.17 nm/min in 70 W of rf power. The capacitance of SBN thin films were increased with the increase of Ar/$O_2$ ratio, rf power and deposition temperature respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.126-130
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• 2008

In this study, in order to develop low loss multilayer piezoelectric actuator, PZN-PZT ceramics were fabricated using $Li_2CO_3,\;Bi_2O_3$, CuO and ZnO as sintering aids, their structural, piezoelectric and dielectric characteristics were investigated according to the amount of ZnO addition, At the sintering temperature of $870^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of 0.4 wt% ZnO added specimen (sintered at $870^{\circ}C$) showed the optimum value of $7.812g/cm^3$, 0.535, 916, 1399, 335 pC/N respectively. Taking into consideration above piezoelectric properties of the specimen sintered at low temperature, it was concluded that PZN-PZT ceramics using 0.4 wt% ZnO as additive showed the optimum characteristics as the composition ceramics for low loss multilayer piezoelectric actuator application.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.215-224
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• 1991

The synthesis of SrTiO3 powders having high purity and homogeneous submicron particle size was attempted by the oxalate method. The microstructure and dielectric properties of SrTiO3 based boundary layer capacitor (BLC) were investigated. Strontium titanyl oxalate[SrTiO(C2O4)2.4H2O] was prepared from the mixing solution of (Sr, Ti) using oxalic acid(H2C2O4) as a precipitating agent at 8$0^{\circ}C$. The crystalline SrTiO3 powder was obtained by thermal decomposition of the precipitate above $600^{\circ}C$. The crystalline SrTiO3 powder containing Nb2O5 as a dopant, TiO2 and SiO2 as additives was sintered at 1360~144$0^{\circ}C$ in the reducing atmosphere to get semiconductive SrTiO3. Insulating material containing PbO-Bi2O3-B2O3 frit was printed on the sintered semiconductive SrTiO3 and fired at 120$0^{\circ}C$ for 2h to get the grain boundary diffusion.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.544-547
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• 2009

The $Sr_{0.7}Bi_{2.3}Nb_{2}O_{9}$(SBN) thin films are deposited on Pt-coated electrode(Pt/Ti/$SiO_2$/Si) using RF sputtering method at various deposition temperature. The optimum conditions of RF power and Ar/$O_2$ ratio were 60[W] and 70/30, respectively. Deposition rate of SBN thin films was about 4.17[nm/min]. The crystallinity of SBN thin films were increased with increase of deposition temperature in the temperature range of $100{\sim}400[^{\circ}C]$, the surface rougness showed about 4.33[nm]. The capacitance of SBN thin films were increased with the increase of deposition temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.44-47
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• 1995

In this study, dielectric and piezoelectric properties of 0.4[0.1Bi(Ni$\_$1/2/Ti$\_$1/2/)O$_3$0.9Pb(Ni$\_$1/3/Nb$\_$2/3/)O$_3$]-0.6(PbZr$\_$y/Ti$\_$1-y/)O$_3$ceramics with Zr/Ti ratio were observed. As a results, structure of the ceramics with ZrO$_2$(y) 0.425 and 0.45 was MPB. Electromechanical coupling coefficients k$\_$p/, k$\_$31/ of the BN$\_$162/ specimen were 57.2%, 35.6% and piezoelectric constants d$\_$33/, d$\_$31/ were 720, 298[x10$\_$-12/C/N).

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.838-840
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• 1998

$BiNbO_4$ ceramics with 0.06wt% CuO, 0.1wt% $V_{2}O_{5}$ sintered at $900^{\circ}C$. The strip line chip filter has been design and fabricated by screen printing with silver electrode after tape casting. The characteristics of the fabricated filters were compared with the simulated results. In the strip line chip filter, insertion loss value of band pass width was 3.65[dB] and return loss was 8.9[dB] and center frequency was similar that simulation results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.193-195
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• 2005

[ $0.96[Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3]+0.04SrTiO_3+0.3wt%Nb_2O_5+0.2wt%La_2O_3+xwt%ZnO$ ], were studied in order to develope the superior piezoelectric properties of Lead-free piezoelectric ceramics. With increasing amount of ZnO addition, density showed the maximum value of 5.79(g/$cm^3$) at 0wt% ZnO addition, and electromechanical coupling factor($k_p$) and dielectric constant decreased, and mechanical quality factor($Q_m$) increased and showed the maximum value of 280 at 0.4wt% ZnO addition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.867-871
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• 2013

The Ti adhesion layers were deposited onto the glass substrate for transparent capacitors using $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMNO) dielectric thin films. Graphene was transferred onto the Ti/glass substrate after growing onto the Ni/$SiO_2$/Si using rapid-thermal pulse CVD (RTPCVD). The BMNO dielectric thin films were investigated for the microstructure, dielectric and leakage properties in the case of capacitors with and without Ti adhesion layers. Leakage current and dielectric properties were strongly dependent on the Ti adhesion layers grown for graphene bottom electrode.