• 한국세라믹학회지
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• 제33권10호
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• pp.1117-1123
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• 1996

• 한국전기전자재료학회논문지
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• 제17권8호
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• pp.830-834
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• 2004

In this study, lead-free pirzoelectric ceramics were investigated for pressure sensor applications as a function of the amount of ${La}_2{O}_3$ addition at $Bi(Na, K)Ti{O}_3-SrTi{O}_3$system. With increasing the amount of addition, the density and dielectric constant increased up to 0.9 wt% ${La}_2{O}_3$ addition and decreased above 0.9 wt% ${La}_2{O}_3$addition. Electromechanical coupling factor( $K_{P}$) showed the maximum value at 0.2 wt% ${La}_2{O}_3$addition and decreased above 0.2 wt% ${La}_2{O}_3$ addition. Electromechanical coupling $factor{(K)}_P$, density, dielectric constant$(\varepsilon_\Gamma)$, piezoelectric constant$(d_33)$ and curie temperature$(T_C)$ showed optimum value of 0.40, 5.75 g/㎤, 768, 215 pC/N and 320 $^{\circ}C$ at 0.2 wt%${La}_2{O}_3$addition, respectively.

• Transactions on Electrical and Electronic Materials
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• 제7권3호
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• pp.123-128
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• 2006

The microstructure and electrical properties of the varistors, which are composed of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-La_2O_3-based$ ceramics, were investigated for different $La_2O_3$ contents. The increase of $La_2O_3$ content led to more densified ceramics, whereas abruptly decreased the nonlinear properties by incorporating beyond 1.0 mol%. The highest nonlinearity was obtained from 0.5 mol% $La_2O_3$, with the nonlinear coefficient of 81.6 and the leakage current of $0.2{\mu}A$. The increase of sintering time and temperature greatly decreased the nonlinear properties. As the $La_2O_3$ content increased, the donor density increased from $0.64\times10^{18}/cm^3\;to\;16.89\times10^{18}/cm^3$ and the barrier height greatly decreased with increasing $La_2O_3$ content, reaching a maximum (1.47 eV) in 0.5 mol% $La_2O_3$.

• 한국세라믹학회지
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• 제28권4호
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• pp.261-268
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• 1991

The dielectric properties and microstructure of SrTiO3-based grain boundary layer (GBL) capacitor were investigated, and SrTiO3 GBL capacitor was made by penetrating the Frit (PbO-Bi2O3-B2O3 system). The Nb2O5-doped SrTiO3 ceramics were fired for 4-hours, at 145$0^{\circ}C$ in H2-N2 atomsphere to get semiconductive ceramics. The grain size of SrTiO3 sintered at reduction atmosphere had increased as the amount of Nb2O5 increases and then decreased as the amount of Nb2O5 exceeded 0.2 mole%. Insulating reagents which contained PbO-Bi2O3-B2O3 system frit and oxide mixture were printed on the each semiconductive ceramics and fired at varying temperature and for different holding time. The optimum dielectric properties could be obtained by second heat treatment at 110$0^{\circ}C$ for 1 hour, when frit paste was printed. A SrTiO3-based GBLC had the apparent permitivity of about 3.2$\times$104, the dielectric loss of 0.01~0.02 and the stable temperature coefficient of capacitance. The influence of frit paste on dielectric properties was similiar to that of oxide paste but the stability of temperature property of capacitance was improved.

• 한국세라믹학회지
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• 제29권8호
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• pp.667-673
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• 1992

The alumina-zirconia composite powders of core particle ZrO2 coated with Al2O3 were prepared by the hydrolysis-deposition of the mixed aluminum salt solution of Al2(SO4)3-Al(NO3)3-Urea. The effects of hydrolysis reaction and coating parameters on characteristics of coated powders and composites were also investigated. The degree of coating could be estimated from the ratio of tetra-/mono-ZrO2 present at the room temperature after heat-treating coated powders at 120$0^{\circ}C$ and the result of TEM observations. When the content of ZrO2 in the dispersed coating system, the coating time, and the volume ratio of water/solution were 50 mg/g, 180 min, and 5, respectively the coating efficiency was maximum (the ratio of tetra-/mono-ZrO2 was 87/13). The relative densities of coated Al2O3-ZrO2 composites sintered at 1$650^{\circ}C$ for 4 hrs were about 91~98% and the maximum ratio of tetra-/mono-ZrO2 in Al2O3-20wt% ZrO2 composites was 62/38.

• 한국세라믹학회지
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• 제31권10호
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• pp.1240-1246
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• 1994

While sintering the Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system through solid-reaction route, pyrochlore(Pb3Nb4O13) phase while reduces the dielectric constant is inevitably formed. Substitution of Pb(Mg1/3Nb2/3)O3 with PbTiO3 and BaTiO3 can retard the occurrence of pyrochlore phase. The perovskite solid-solution without containing pyrochlore phase can be obtained when we consolidated the materials consisting of PbTiO3 and BaTiO3 at 1200℃ for 2 hours. The sintered body composed of 0.8Pb(Mg1/3Nb2/3)O3-0.1PbTiO3-0.1BaTiO3 composition showed the diffused phase transition(DPT) phenomena and the maximum value of dielectric constant at 0℃ (Tc') with the value of 1.3×104.

• 한국세라믹학회지
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• 제37권2호
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• pp.117-121
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• 2000

Er-doped sodiumborosilicate glass films for waveguides amplifier were fabricated by Aerosol Flame Deposition(AFD) method. Al2O3 was added to sodium borosilicate glass films to suppress the formation of crystalline phase and control the refractive index. the formation of crystalline phase was suppressed above Al2O3 of 6 wt%. As the amount of Al2O3 increased from 2 to 12 wt% the refractive index of glass films increased lineary from 1.4595 up to 1.4710. After the core of 77SiO2-15B2O3-8Na2O＋6 wt%Al2O3＋8wt%Er2O3 was coated on the buffer layer of 77SiO2-15B2O3-8Na2O＋6 wt%Al2O3, the core was etched by reactive ion etching. The absorption spectrum of 3 cm waveguide amplifier showed two peaks of 1530 and 1550 nm.

• 한국세라믹학회지
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• 제28권3호
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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.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.95-96
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• 2000

The effect of $Al_2O_3$ on the dielectric constant and the coefficient of thermal expansion of lead borosilicate glasses for the application of PDP glass paste was investigated. Measurements were made theoretically by using empirical equations on the composition of the of glasses in which the $PbO/Al_2O_3$, $B_2O_3/Al_2O_3$ and $SiO_2/Al_2O_3$ ratios were systematically varied. As a result, with increasing $PbO/Al_2O_3$ the thermal expansion coefficient and the dielectric constant noticeably increased, while the change of $B_2O_3/Al_2O_3$ and $SiO_2/Al_2O_3$ ratios did not affect those properties of the glasses.

• 청정기술
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• 제21권1호
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• pp.39-44
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• 2015

본 연구에서는 다섯 종의 씨앗(춘채, 아욱, 양배추, 배추, 당근)을 이용하여 금속산화물 나노입자(CuO, NiO, Fe₂O₃, Co₃O₄, TiO₂, ZnO)들이 씨앗발아와 발아지수에 미치는 영향을 조사하였다. CuO, ZnO, NiO 나노입자는 씨앗 활성에 뚜렷한 독성 영향을 나타내었으며, 나노입자종류에 따라 상이한 민감도를 나타내었다. 각 나노입자에 대한 독성순서(EC₅₀ 범위)는 다음과 같다: CuO 6~27 mg/L > ZnO 16~86 mg/L > NiO 48~112 mg/L. 나머지 조사 대상 나노입자인 Co₃O₄, TiO₂, Fe₂O₃은 최대 1,000 mg/L 높은 농도 노출에도 뚜렷한 영향을 나타내지 않았다. 씨앗별 상이한 민감도를 나타내었으며, 가장 민감한 종인 아욱의 씨앗발아 EC₅₀은 CuO 5.5 mg/L ZnO 16.4 mg/L, NiO 53.4 mg/L로 조사되었다. 씨앗별 나노입자에 대한 독성 영향은 CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂ 나타났으나, 당근씨앗은 NiO [EC₅₀ 80.4(71.41~90.54) mg/L]와 ZnO [EC₅₀ 85.8(69.31~106.29) mg/L]가 유사한 독성을 나타내었다.