• 한국세라믹학회지
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• 제55권2호
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• pp.140-144
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• 2018

$ZnO/TiO_2$ nanocomposites were synthesized via a modified sol-gel technique by incorporating 30 and 70 wt% $TiO_2$ nanopowder into a ZnO sol-gel matrix. Zinc acetate dihydrate was used as the ZnO precursor and de-ionized water as the solvent, while titanium oxysulfate was employed for the synthesis of $TiO_2$ nanopowder. The synthesized $ZnO/TiO_2$ nanocomposites were characterized by x-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. The $ZnO/TiO_2$ nanocomposites showed both the ZnO (wurtzite) and $TiO_2$ (anatase) phases. The average ZnO crystallite size of the $ZnO/TiO_2$ nanocomposites was found to be about 26.3 nm. The TEM results confirmed that spherical $TiO_2$ particles were embedded in the ZnO matrix. $TiO_2$ particles attached onto the rod-like ZnO particles were also observed. The $ZnO/TiO_2$ nanocomposites exhibited optical absorption properties superior to those of pure ZnO and $TiO_2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.311-315
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• 2000

Vanadate glass in the $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ system containing 10mol% glass fonner, $P_2O_5$ and $Bi_2O_3$ was prepared by melting the batch in pt. crucible followed by Quenching on the copper plate. We found that $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass-ceramics obtained from nucleation of glass showed signifieantly higher capacity and longer cycle life than conventionally made crystalline $LiV_3O_{8}$. In the present paper, we describe the charge / discharge properties during crystallization process and find the best crystallization condition of $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass as cathod material.

• 한국세라믹학회지
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• 제18권3호
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• pp.187-191
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• 1981

The effect of additions, $TiO_2$ and $ZrO_2$ as nucleant on the base glass which composition was determined to 0.97 $Li_2O-Al_2O_3-SiO_2$ has been investigated by means of D.T.A., X-ray diffraction and dilatation. $TiO_2$ and $ZrO_2$ as nucleant were added 0.06mole, in which ratios of $TiO_2$/$ZrO_2$ were varied 1/0, 2/1, 1/1, 1/2 and 0/1. The crystalline phases were appeared to $\beta$-spodumene as principal, $\beta$-eucryptite and $ZrO_2$ as secondary, regardless of nucleant variations. The crystallinity of the crystallized glass added $TiO_2$, $ZrO_2$ mixture as nucleant was higher than that of the glass added $TiO_2$ or $ZrO_2$ only. The crystallinity of the glass added $TiO_2$/$ZrO_2$ =1/1 was highest. Increasing the addition of $ZrO_2$, it has been observed that the crystal growing temperature became higher.

• 한국세라믹학회지
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• 제25권2호
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• pp.117-124
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• 1988

The properties of the powders of the system Al2O3-ZrO2-Y2O3 prepared by precipitation method were investigated. Al2(SO4)3$.$18H2O3, ZrOCl2$.$8H2O and YCl3$.$6H2O were used as starting materials. Amorphous aluminum hydrate prepared by precipitation method was completely transformed to alpha Al2O3 as a result of calcining at 1100$^{\circ}C$ for 1 hr and gamma, delta and theta phases appeared as transition phases. In ZrO2-Y2O3 system prepared by co-precipitation method, the crystallization temperature of ZrO2 was increase with Y2O3 contents. The coupled crystallization occured in coprecipitated Al2O3-ZrO2-Y2O3 system, therefore the formation temperature of alpha Al2O3 and ZrO2-Y2O3 system. In this ternary system, the powder morphology showed a particular shape which was composed of large Al2O3 grains having small spherical ZrO2 particles within large Al2O3 grain and relatively large ZrO2 particles along the grian boundaries.

• 한국세라믹학회지
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• 제27권5호
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• pp.583-588
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• 1990

Glass films in the binary system B2O3-SiO2 and Al2O3-SiO2 were prepared on soda-lime-silica slide glass by the dip-coating technique from TEOS and boric acid or aluminum nitrate. Thickness of the films varying with viscosity and withdrawal speed were measured and effect of composition and firing temperature on the properties such as transmittance and refractive index were investigated. nM2O3.(100-n)SiO2(M=B or Al) films containing up to 20mol% B2O3 and 40mol% Al2O3 were transparent. Maximum transmittance at visible range were obtained for the sample containing 15mol% Ba2O3 and 32.5mol% Al2O3 and heat-treated at 50$0^{\circ}C$, respectively. Refractive index of the film containing 15mol% B2O3 was mininum in the B2O3-SiO2 binary system and minimal refractive index was appeared at the film containing 32.5mol% Al2O3. In IP spectra, addition of B2O3 were increased absorption peak intensity of B-O and Si-O-B bond and addition of Al2O3 were decreased absorption peak intensity of Si-O bond, respectively.

• Journal of Ceramic Processing Research
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• 제13권spc1호
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• pp.37-41
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• 2012

A lithium ion conducting borosilicate glass was fabricated by a conventional melt quenching technique from a mixture of Li2CO3, B2O3 and SiO2 powders. The Li ion conductivity of the lithium borosilicate glasses was evaluated in terms of the SiO2/B2O3 ratio. In the Li2O-B2O3-SiO2 ternary glass, the glass forming region decreases with an increasing Li2O content. At the same Li2O, the crystallization tendency of the glass samples increases with the SiO2/B2O3 ratio, resulting in a reduced glass forming region in the Li2O-B2O3-SiO2 ternary glass. The electrical conductivity moderately depends on the SiO2/B2O3 ratio in the Li2O-B2O3-SiO2 ternary glass. The conductivity of the glasses slightly increases with the SiO2/B2O3 ratio. The observed phenomenon can be explained by the modification of the glass structure as a function of the SiO2 content.

• 한국세라믹학회지
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• 제30권3호
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• pp.199-205
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• 1993

Effects of grain size distribution on the breakdown voltage of ZnO varistors were investigated in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems, respectively. The grain size was increased with increasing sintering temperature maintaining lognormal distribution in both systems. The width of grain size distribution of ZnO-Bi2O3-CoO-Sb2O3 system was narrower than that of ZnO-Bi2O3-CoO-Sb2O3 system. The breakdown voltage(Vb) was decreased by increasing sintering temperature(1000~135$0^{\circ}C$) and sintering time(0.5~5hr), due to the enhancement of ZnO grain growth. The current path of the ZnO varistor was dependent on the distribution of the largest grains (chains of long grains) between the electrodes.

• 한국세라믹학회지
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• 제32권1호
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• pp.106-112
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• 1995

In order to examine the effect of CuO and Al2O3 addition on the electrical conductivity of ZnO, both Al2O3 (0, 1, 2, 5, 10at.%) and CuO (1, 5at.%) were added to ZnO. Al2O3 addition (~2at.% Al) increased the total electrical conductivity of ZnO which was already decreased by CuO doping effect Above solid solubility of Al (~2at.%), ZnAl2O4 formed and the total electrical conductivity decreased due to the decrease of sintered density. Impedance measurements were used to know the reason and degree of contribution of three resistive elements, ZnO grain, ZnO/CuO, and ZnO/ZnO grain boundaries, to the total electrical conductivity changed.

• 한국세라믹학회지
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• 제34권2호
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• pp.123-130
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• 1997

본 연구에서는 유전상수가 크고, 유전체 손실이 적으며, 사용온도 범위에서 정전용량 변화율(TCC : tem-perature coefficient of capacitance)이 작고, 고압에 견딜 수 있는 재료를 개발하기 위하여 중고압용 capacitance의 기본재료로써 (Sr.Pb.Ca)TiO3-xBi2O3.3TiO2 계에서 Bi2O3.3TiO2의 mol.%를 5, 6, 7, 8, 9 mol.%로 변화시켰으며, 그 결과 고용한계 함량이 6mol.%이며, 6mol.%이상에서는 침상구조의 증가에 기인하여 유전율이 다시 감소하는 경향을 보였다. dopant로써 SiO2, Nb2O3, MnO2를 선정하여 첨가한 결과, MnO2를 첨가한 것이 유전성질이 가장 우수하였으며, MnO2의 함량이 0, 0.15, 0.3, 0.45 wt.% 증가함에 따라서 유전율의 감소와 동시에, TOC특성의 급격한 향상을 가져왔다.

• 한국세라믹학회지
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• 제36권7호
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• pp.734-741
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• 1999

Al2O3와 t-ZrO2 분말의 압분체를 공기중 150$0^{\circ}C$ 및 1$600^{\circ}C$에서 2시간 소결하여 제조된 입자복합체의 미세구조와 기계적 성질을 조사하였다. 소수의 미세한 구상의 ZrO2입자는 Al2O3의 입내에 존재하였으나 대분분은 입계에 존재하여 Al2O3의 입계를 고정시키는 것이 가능하였고, 따라서 Al2O3의 입성장을 둔화시켰다. 소결할 동안 입계 ZrO2 입자의 조대회는 응집된 ZrO2 입자내에서의 입계의 소멸과 Al2P3 입계의 이동에 의해서 끌어 당겨진 ZrO2 입자의 합체(coalescence)에 의해서 일어날 수 있었다. ZrO2의 첨가에 의한 Al2O3의 기계적 성질의 변화는 기지상인 Al2O3의 미세구조와 분산된 ZrO2 입자의 크기와 구조에 의존하였다.