• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.37-45
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• 2003

The dielectric and sintering characteristics of composites made by substituting Ca ion to Ba-site and Zr ion to Ti site in $(Ba{1-x}Ca_x)(Ti{0.96-yZr_ySn_{0.04})O_3$ $(0.15{\leq}x{\leq}0.20,\;0.09{\leq}y{\leq}0.14)$ were investigated. As the content of Ca was more than 15 mol%, composite was formed by precipitating the second phase whose main element was $CaTiO_3$ and the fraction of the second phase was increased. The curie temperature of composites was depended on Ca concentration, $-1.7^{\circ}C$ per mol% and the maximum dielectric constant of composite was decreased by the rate of 200/mol%. The substitution of Zr ion decreased the curie temperature by the rate of $10^{\circ}C$ per mol% and the maximum dielectric constant was decreased by 217/mol% due to the increase of diffuse phase transition. The density and insulation breakdown characteristics were improved by suppressing the abnormal grain growth due to the increase of second phase. We developed the composition of Y5U (EIA standard) condenser which had high breakdown voltage and dielectric constant by controlling diffuse phase transition by the addition of Zr ion into composite.

• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.491-497
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• 1987

$ThO_2-Tm_2O_3$ (TDT) solid solutions containing 1,3,5,8,10, and 15 mol% $Tm_2O_3$ were synthesized from spectroscopically pure $ThO_2$ and $Tm_2O_3$ polycrystalline powders. The TDT solid solutions were indentified to the fluorite structure by the X-ray powder technique. The values of the lattice parameter were decreased with increasing amount of $Tm_2O_3$ incorporated. But, there was no linearity for the samples containing 8, 10, and 15 mol% $Tm_2O_3$. It was concluded that these samples became incomplete solid solutions. From the intensity analyses of X-ray diffraction patterns, the residual factor was found below 0.13 even for the 15 mol% TDT system. lt was confirmed from the DTA and TGA analyses that any phase transitions did not occur under the experimental condition executed. Comparing the pycnometric density with the lattice parameter obtained from XRD, it was suggested that the predominant defect model be an oxygen vacancy.