• 한국세라믹학회지
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• 제26권3호
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• pp.423-437
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• 1989

Al2O3/ZrO2 composites were prepared by precipitation method using Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O as starting materials and NH4OH as a precipitation agent. Al2O3/ZrO2 composites(series A) were prepared by mixing Al2O3 powder obtained by single precipitation method with ZrO2(＋3m/o Y2O3) powder obtained by co-predipitation method. Al2O3/ZrO2 composites (series B) were prepared by co-precipitation method using the three starting materials. In all cases, the composition was controlled as Al2O3-15v/o ZrO2(＋3m/o Y2O3). The composites of series A showed higher final relative densities than those of series B and tetagonal ZrO2 in all cases was retained to about 95% at room temperature. ZrO2 particles were coalesced more rapidly in grain boundary of Al2O3 than within Al2O3 grain. ZrO2 particles were located at 3-and 4-grain junction of Al2O3 and limited the grain growth of Al2O3. It was observed that MgO contributed to densification of Al2O3 but limited grain growth of Al2O3 by MgO was not remarkable. In all Al2O3/ZrO2 composites, exaggerated grain growth of Al2O3 was not observed and Al2O3/ZrO2 composites were found to have homogeneous microstructures.

• 한국세라믹학회지
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• 제44권11호
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• pp.639-644
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• 2007

Spinel pigments, developing black color in high temperature glazes at oxidation or reduction atmosphere, without CoO because of its high price were synthesized by solid solution method. Ten mixed compositions consisted of NiO, MnO, $Fe_2O_3 and $Mn_2O_3$ were fired at $1250^{\circ}C$ for 1h. The resulting pigments were characterized by using XRD, FT-IR, SEM and UV-vis spectrometer. Structure of the pigments are spinel and particles' shape are spherical or cubic. Glazed tiles containing 5 wt% pigments were fired at $1260^{\circ}C$ and $1240^{\circ}C$ in reduction atmosphere. Color in glazes were analyzed by UV-vis spectrometer. Colors of NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole% in lime glaze showed black in oxidation, in reduction NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.55{\cdot}Mn_2O_3$ 0.0125 mole% showed black. In case of lime-barium glaze, NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.975 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black color in oxidation and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.725 MnO $0.275{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black one in reduction.

• 한국세라믹학회지
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• 제24권1호
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• pp.33-40
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• 1987

The investigation includes phase equilibria of Al2O3-HfO2 Cr2O3-ZrO2, Cr2O3-HfO2, Al2O3-Cr2O3-ZrO2, Al2O3-Cr2O3-HfO2, Al2O3-ZrO2-HfO2, Cr2O3-ZrO2-HfO2, Al2O3-Cr2O3-ZrO2-HfO2. In the systems the solubility near the end members has been studied at 1500$^{\circ}C$ and 1600$^{\circ}C$, respectively. Selective Compositions were investigated in the area of the guarternary system where the phae relation was examined.

• 한국세라믹학회지
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• 제41권1호
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• pp.57-61
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• 2004

Zinc Oxide (ZnO)은 wurtzite 결정구조를 가지고 있으며, 밴드갭 에너지가 약 3.3eV로 반도성 산화물이다. $In_2O_3$이 첨가된 ZnO 박막을 점자빔증착법을 이용하여 1737F 유리기판에 제조하였다. $400^{\circ}C$의 증착온도에서 $In_2O_3$의 첨가량에 따른 ZnO 박막의 결정성, 미세구조를 비롯한 전기.광학적 특성을 조사하였다. 첨가되는 $In_2O_3$의 양에 따라 투명전도성 산화막으로써의 ZnO 박막의 특성이 변화되었다. $In_2O_3$의 첨가량이 감소할수록 비정질상에서 결정성의 ZnO 막을 얻을 수 있었다. 0.2at%의 $In_2O_3$가 첨가된 출발물질에서 제조된 $In_2O_3$-doped ZnO막은 약 $6.0 {\times} 10^{-3} {\Omega}cm$ 정도의 비저항값과 가시광선 영역에서 85% 이상의 광투과도를 나타내었다.

• 한국세라믹학회지
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• 제27권8호
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• pp.991-1003
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• 1990

A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent, various types of metal hydroxides were obtained by single precipitation(series A) and co-precipitation(series B) method at the pH condition between 7 and 11. Fine Al2O3-ZrO2 powders were prepared at optimum calcination condition and the effects of ZrO2 on microstructures and mechanical properties of Al2O3 were investigated. The composition of Al2O3/ZrO2 composites wax fixed as Al2O3-15 v/o ZrO2(＋3m/o Y2O3). ZrO2 limited the grain growth of Al2O3 and increased grain size homogeneity of Al2O3 more effectively than MgO.Flexural strength values in Al2O3 and Al2O3/ZrO2 composites were 340-430 MPa and 540-820 MPa, respectively, and the effect of strength improvement showed 20-50% by adding ZrO2 to Al2O3. Fracture toughness of Al2O3/ZrO2 composites was improved by stress-induced phase transformation of tetragonal ZrO2 and toughening effect by microcrack was not observed. Also, ZrO2 particles located at Al2O3 grain junction contributed to toughening, while spherical ZrO2 particles located within Al2O3 grain did not contribute to toughening. Weibull moduli of Al2O3 ceramics and Al2O3/ZrO2 composites of series A and series B were 4.34, 5.17 and 9.06, respectively. Above 0.5 of failure probability, strength values in Al2O3 ceramics and Al2O3/ZrO3 composites of series A and series B were above 400 MPa, 700 MPa and 650 MPa, respectively.

• 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.

• 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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• 제29권2호
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• pp.101-106
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• 1992

Sintering behavior, distribution of dopant oxides and electrical properties in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems were studied. The linear shrinkage of ZnO varistors from 850 to 950$^{\circ}C$ was related to the decomposition reaction (py\longrightarrowsp+Bi2O3) of the pyrochlore phase. In the distribution of the dopant oxides (CoO, Sb2O3, Cr2O3), Co distribute uniformly throughout the sample, the distribution of Sb coincided with small particles (spinel phase, Zn7Sb2O12), and Cr distributed very consistently with Sb. The increase in breakdown voltage, due to the addition of Cr2O3, was not only attributed to the decrease in the ZnO grain size but also to the solution of Cr2O3 in the spinel phase. The leakage current (80% V60 ${\mu}\textrm{A}$) was increased by the addition of Cr2O3.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.543-546
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• 2004

The melting temperature and critical temperature(Tc) of $YBa_2Cu_3O_x$ with deferent content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as addition in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity(the transition width, ${\Delta}T_c$) became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and in the sample $BaPbO_3$ became the main phase. Therefore the superconductivity was reduced. $BaPbO_3$ was chosen as the impurity for the comparative study. The single phase BaPbO3 was synthesized by the simple way from both mixtures of $BaPbO_3$ and PbO, $BaPbO_3\;and\;PbO_2$. Deferent contents of $BaPbO_3$(10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the phase analysis in the XRD patterns it was proved that there werenot reactions between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as impurity in $YBa_2Cu_3O_x$. But the melting point of $YBa_2Cu_3O_x$ with $BaPbO_3$ could not be found when the temperature was lower than $1000^{\circ}C$ in the DTA measurement.

• 한국세라믹학회지
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• 제26권2호
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• pp.210-220
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• 1989

The properties of the powder of Al2O3-15v/o ZrO2(＋3m/o Y2O3) system prepared by co-precipitation method at the pH values of 7, 9, 10 and 11 were investigated. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent. Zirconium hydroxide decreased the specific surface area of aluminum hydroxide of AlOOH type, while increased the specific surface area of aluminum hydroxide of Al(OH)3 type, and formed co-network structure of Al-O-Zr type with the aluminum hydroxides. The rate of transition to $\alpha$-Al2O3 from co-precipitated materials occurred in the order of 7≒10, 9 and 11 of pH values. Al2O3 and ZrO2 interacted to bring about coupled grain growth, and the growth of ZrO2 crystallite size rapidly occurred within $\theta$-Al2O3 matrix. Segregation did not occur in the system Al2O3-15v/o ZrO2(＋3m/o Y2O3) and Y2O3 acted as a stabilizer to ZrO2. The lattice strain of tetragonal ZrO2 was increased by the constraint effect of Al2O3 matrix.