• 한국세라믹학회지
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• 제34권11호
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• pp.1113-1120
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• 1997

The 2, 4, 6 and 8mol% Y2O3 doped-ZrO2 powders (20 kinds) with the addedtion of Al2O3 upto 8wt% were prepared by coprecipitation method using the zirconium oxyacetate, yttrium chloride and aluminum nitrate as starting materials. The coprecipitated powders were characterized by XRD, TG-DTA, FT-IR and SEM. The sintering properties of zirconia-alumina composites prepared by 2YSZ and 8YSZ powders containing various Al2O3 contents were also investigated. With increasing the yttria stabilizer contents, the amount of exothermic heat for zirconia crystallization decreased. And it was confirmed that the crystallizing temperature of coprecipitated zirconia powders increased and the crystallization process occurred in a wide temperature range, as Al2O3 content increased in 8YSZ.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1514-1517
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• 2005

The $(Y,Gd)BO_3:Eu^{3+}$ phosphor was made by coprecipitation method. The precipitated powders were amorphous. The value of pH in the process of coprecipitation was critical for the luminescence of phosphors. The particle size and morphology were influenced by pH value. The lower calcination temperature and hydrothermal synthesis leads to the distortion of lattices. The distorted lattices changed the symmetry of $Eu^{3+}$ site. The broken inversion symmetry in the distorted lattice caused the increased emission of $^5D_0{\rightarrow}^7D_2$ transition.

• 한국세라믹학회지
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• 제33권5호
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• pp.563-571
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• 1996

In order to fabricate solid electrolyte CaO-stabilized ZrO2 of high density sintered body economically 13 mol% CaO-stabilized ZrO2 powders were synthesized by the coprecipitation method. The characteristics and sintering behavior of fine powder were investigated. The precipitates has the specific surface area of 193 m2/g and apperaed to be fine and spherical primary particles with a size of approximately 5nm. The crystalliza-tion temperture of CaO-stabilized ZrO2 was 462$^{\circ}C$. The tetragonal phase was stable in the low calcining tempe-rature regions and the cubic zirconia solid solution was formed from above 120$0^{\circ}C$ through an intermediate stage of formation of CaZrO3 By introducing fine powders washed with alcohol and ball-milling process after calcination the sintered body was possible to attain the value of above 92% of the theoretical density at low temperature of 120$0^{\circ}C$.

• 한국세라믹학회지
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• 제34권10호
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• pp.1045-1052
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• 1997

Barium ferrites (BaFe12O19) were synthesized at the various temperature by the coprecipitation-oxidation method. X-ray diffraction Rietveld analysis for barium ferrites were performed, their microstructures were observed and their magnetic properties were measured, in order to analyze the crystal structures and determine the optimal temperature of heat-treatment. The barium ferrite, its average particle size 80 nm, was formed at 600℃ through the hematite (α-Fe2O3), but the site occupations of the Fe's in tetrahedral and bipyramidal sites and of the Ba relatively low. Increasing the heating temperature, these occupations and the magnetization increased, and the crystal c-axis decreased. These changes were very small at the heat treatment of above 800℃, but the particles were rapidly grown. It is suggested that the optimal temperature of heat-treatment is 800℃, at which temperature crystal structure is relatively stable and the particles hardly ever grow.

• 한국세라믹학회지
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• 제25권6호
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• pp.671-676
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• 1988

Preparation of high purity ultrafine Ba2Ti9O20 powder was investigated by coprecipitation method. Formation of Ba2Ti9O20 powder from precipitate of coprecipitation takes place at 120$0^{\circ}C$, which is 20$0^{\circ}C$ lower than that from mechanical mixtures of BaCO3 and TiO2. This is apparently due to the nature of the compounds formed by the reaction of mixtures of aqueous solutions of BaCl2 and TiCl4 with an ammoniacal solution of ammonium carbonate and ammouium hydroxide. In this method, the Ba2Ti9O20 powders show low callcining and sintering temperature and it has good sintering and dielectric constant at room temperature.

• 한국세라믹학회지
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• 제22권5호
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• pp.17-22
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• 1985

This study was to make powder by coprecipitation method and spray dispersion precipitation method in $(1-x)ZrO_2-xMgO$ system to improve sinterability. As the result the specific surface area of powder prepared by spray dispersion precipitation method and coprecipitation method was above $110m^2/g$ and $10-20m^2/g$ respectively. Spray dispersion precipitation method was more effective than coprecipitation method in powder preparation.

• 한국세라믹학회지
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• 제27권1호
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• pp.62-66
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• 1990

La-modified PbTiO3 Powders and ceramics were prepared by coprecipitation and salt decomposition method. In this process, fine and homogeneous single phase of La-modified PbTiO3 was synthesized at lower temperature than oxide mixing method. And these powders contributed to lowering calcination temperature and rising sintering properties. The properties of these powders and the change of properties with themperature and the effect of powder properties on sintering were investigated.

• 한국세라믹학회지
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• 제25권4호
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• pp.315-320
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• 1988

The Nb doped BaTiO3 was synthesized by coprecipitation method using H2O2 media in region from pH 8 to pH 11. The powder prepared by using this method was crystallized at about 20$0^{\circ}C$ and average particle size was controlled by heat treatment. Because of preparation having fine particle and relatively narrow particle size distribution, high performance PTC device was made of these precipitated powders.

• 한국세라믹학회지
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• 제30권6호
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• pp.478-484
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• 1993

The influence of reaction conditions on the MnZn ferrite coprecipitation process were investigated using mixed metla sulfate solution and ammonium oxalate. In order to minimize the metallic ion losses and to control the particle size, the optimum reaction conditions were as follows; reaction temperature $25^{\circ}C$, metal sulfate concentration 0.3M, molar ratio of ammonium oxalate/mixed metal sulfate 1.1:1. The production yield was as high as 97.6% of theoretical yield at optimum reaction condition.

• 한국세라믹학회지
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• 제27권3호
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• pp.389-393
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• 1990

PLZT(9/65/35) powders and ceramics were obtained by coprecipitation method from aqueous salt solution and its powder and sintering properties were investigated. Single phase of PLZT was synthesized about 53$0^{\circ}C$ and its average particle size was 1${\mu}{\textrm}{m}$. Specimen which was sintered at 1275$^{\circ}C$ for 30 hours under 1atm and PbZrO3 atmosphere powders, showed 45% of optical transmittance in visible range for 0.27mm thickness sample.