• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.134-137
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• 2000

Zirconia films stabilized b $Y_2O_3$, YSZ, films were deposition by metal organic chemical vapor deposition (MOCVD) onto various kind of substrates. $Y_2O_3$, $ZrO_2$and the mixtures of these two were deposited and characterized. The deposition rate, the film composition and the structure could be systematically varied through the $Y(C_{11}H_{19}O_2)_3$, Zr(O.t-$C_H_9)_4$source gas ratios and the deposition temperature. The Y/Zr ratio in YSZ film could be adjusted by controlling the ratio of $Y(C_{11}H_{19}O_2)_3$, Zr(O.t-$C_4H_9)_4$partial pressures. This is because the ratios of the deposition rates of Y and Zr atoms in $Y_2O_3$and $ZrO_2$films to those in YSZ films, Ф, are constant irrespective of the input gas concentration. However, the Y/Zr ratio was found to be smaller than that estimated based on the deposition rates of un-mixed $Y_2O_3$and $ZrO_2$films. This is because the Фs of Y and Zr atoms are not equal. The activation energy of $Y_2O_3$component in YSZ films was similar to that of $ZrO_2$component in YSZ films. These YSZ values were more than 4 times larger than those of un-mixed $Y_2O_3$or $ZrO_2$films.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.191-193
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• 2004

The composites were fabricated, respectively, using 61vol.% SiC-39vol.% $TiB_2$ and using 61vol.% SiC-39vol.% $ZrB_2$ powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ by hot pressing annealing at $1650^{\circ}C$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H, 3C), $TiB_2$, $ZrB_2$ and $YAG(Al_5Y_3O_{12})$ crystal phase on the SiC-$TiB_2$, and SiC-$ZrB_2$ composites. The ${\beta}\;{\alpha}$-SiC phase transformation was occurred on the $SiC-TiB_2$, $SiC-ZrB_2$ composites. The relative density, the flexural strength and Young's modulus showed respectively value of 98.57%, 226.06Mpa and $86.37{\times}10^3Mpa$ in SiC-$ZrB_2$ composites.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.653-658
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• 1998

ZrO2, B2O3 및 AI을 사용하여 SHS법에 의한 붕화지르코늄을 합성을 하고 산화철과 알루미늄 분말의 첨가가 합성물의 치밀화에 미치는 영향에 대하여 검토하였다. 합성물중에 존재하는 결정상은 대부분이 ZrB2와 $\alpha$-AI2O3상이었다. 산화붕소와 알루미늄의 몰비가 1.0:3.3이상일 때 합성물의 치밀화는 크게 증가하였고, ZrB2 입자도$\alpha$-AI2O3용융상과 더불어 조대하였다. 산화철 1목에 대하여 알루미늄을 1-3몰을 첨가한 것과 산화철 1.5몰에 대하여 알루미늄을 3몰 첨가시 $\alpha$-AI2O3를 중심으로하는 슬라그상으로부터 용융상의 분이가 가능하였고, 이들 용융상에 존재하는 결정상은 ZrB2이외에 Fe, Fe2B, Zr2Fe상이었다. 용융상의 상대밀도는 산화철 1몰에 대하여 알루미늄을 1몰 첨가시 83.2%인 반면에 그 이상의 첨가량에 대해서는 치밀화는 크게 증가하여 알루미늄을 3몰 첨가한 경우 상대밀도는 93.7%로서 최대를 나타내었다.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.21-26
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• 1986

In this study the system of $Pb(Mn_{1/3} Nb_{2/3})O_3-PbTiO_3-PbZrO_3$ piexoelectric ceramics was made in the radial mode disk and attenuation characteristic of the desinged ladder type filter was investigated. What is more temperature dependance of resonant frequency and variation of resonant frequency was examined by chan-ging the electrode diameter of piezoelectric resonator. (A Group : De=11mm, B Group : De=7.5mm and C Gro-up : De=5.5mm) Upon investigation it was the following. The center frequency of A, B and c filter showed up in the 200KHz, 270KHz and 380KHz respectively. As the electrode diameter decreased center frequency in creased abruptly. As the Co_2/Co1 increased attenuation characteristics and selectivity was improved. As the x=50. resonant frequ-ency invaried with variation of temperature.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.98-103
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• 1999

The effect of $Al_2O_3$ additives to $\beta-SiC+39vol.%ZrB_2$ electroconductive ceramic composites by pressureless sintering on microstructural, mechanical and electrical properties were investigated. The $\beta-SiC+39vol.%ZrB_2$ ceramic composites were pressureless sintered by adding 4, 8, 12wt.% $Al_2O_3$ powder as a liquid forming additives at $1950^{\cire}C$ for 1h. Phase analysis of composites by XRD revealed mostly of $\alpha-SiC(6H), ZrB_2$ and weakly $\alpha-SiC(4H), \beta-SiC (15R)$ phase. The relative density of composites was lowered by gaseous products of the result of reaction between \beta-SiC and Al_2O_3$, therefore, porosity was increased with increasing $Al_2O_3$ contents, and showed the maximum value of 1.4197MPa.$m^{1/2}$ for composite with 4wt.% $Al_2O_3$ additives. The electrical resistivity of $\beta-SiC+39vol.%ZrB_2$ electroconductive ceramic composite was increased with increasing $Al_2O_3$ contents, and showed positive temperature coefficient resistance (PTCR) in the temperature range of $25^{\cire}C$ to $700^{\cire}C$.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.255-258
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• 2014

Zirconium boride is an artificial or which is rarely found in the nature. $ZrB_2$ is popular in the hard material industry because it has a high melting point, excellent mechanical properties and chemical stability. There are two known methods to synthesize $ZrB_2$. The first involves direct reaction between Zr and B, and the second is by reduction of the metal halogen. However, these two methods are known to be unsuitable for mass production. SHS(Self-propagating High-temperature Synthesis) is an efficient and economic method for synthesizing hard materials because it uses exothermic reactions. In this study, $ZrB_2$ was successfully synthesized by subjecting $ZrO_2$, Mg and $B_2O_3$ to SHS. Because of the high combustion temperature and rapid combustion, in conjunction with the stoichiometric ratio of $ZrO_2$, Mg and $B_2O_3$; single phase $ZrB_2$ was not synthesized. In order to solve the temperature problem, Mg and NaCl additives were investigated as diluents. From the experiments it was found that both diluents effectively stabilized the reaction and combustion regime. The final product, made under optimum conditions, was single-phase $ZrB_2$ of $0.1-0.9{\mu}m$ particle size.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.935-941
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• 1991

Effects of calcination process and ZrO2 addition on the electrical properties of [(Ba0.82Sr0.08Ca0.1)O]m(Ti1-$\chi$Zr$\chi$)O2 ceramics have been investigated. With the variation of A/B-site ratio m of the dielectric formulations, sintering behavior and the resistivity after sintering in a reducing atmosphere have been affected by the calcination process. When the dielectric formulations of m=1.01 were sintered in a reducing atmosphere, the room-temperature resitivity of 109 {{{{ OMEGA }}.cm was obtained for samples processed with two-step calcination, which was much lower than 1012 {{{{ OMEGA }}.cm of samples calcined once. It was confirmed that high resistivity of Ca-doped BaTiO3 ceramics, after sintering in a reducing atmosphere, is maintained by acceptor-like behavior of CaTi" which is formed by Ca substitution to Ti-site. It was also found out that the critical amount of B-site Ca substitution for reduction inhibition of BaTiO3 is around 0.005 mol. With the increasing amount of ZrO2 addition to dielectric formulations, Curie peak was depressed and Curie temperature was lowered due to the enhanced diffuse phase transition.tion.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.3-8
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• 1985

$ZrO_2$ single crystals were grown by slow cooling flux method using Borax $(Na_2B_4O_7)$ and KF as flux agent. The morphology of grown crystals was observed under a petrographic microscope. And the results obtained from grow crystals were as follows : 1. $ZrO_2$ crystals grown in the present work are morphologically divided into two shapes ; tabular and den-dritic crystals. 2. The maximum size of the crystals grown reaches to $4{\times}15{\times}2mm$ on edge into length at $ZrO_2$ 15mole% Borax 50mole% and KF 35mole% 3. $ZrO_2$ single crystals grown by flux method have monoclinc structure. 4. The content of KF as flux agents was limited by 60mole% KF. Since alumina crucible was heavily damaged by increasing KF content.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.273-278
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• 1983

With the synthetic standards, valuable metals $(Ta_2O_5, Nb_2O_5, TiO_2, SnO_2$, and $ZrO_2$) in the tin slags have been determined by the x-ray fluorescence spectrometry. The powder sample and the standards are homogeneously mixed with anhydrous $Li_2B_4O_7$ and La_2O_3$ in weight ratio of 15 : 42 : 3 respectively. The mixed material is fused at $1,150^{\circ}C$ for 30 minutes to be changed into the glass bead. The bead is ground to (-) 325 mesh size and pelletized. The analytical results obtained in this work are consistent with the data obtained by other common methods within allowable error range. The standard deviation for $Ta_2O_5$ in PTS-H sample is 0.12 % at level of 3.40 % content.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.317-321
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• 2008

The $0.65Pb(Mg_{1/3}Ta_{2/3})O_3-0.35PbTiO_3$ (PMT-PT)ceramics were near morphotropic phase boundary. The dielectric constant, the loss, and pyroelectric coefficient of the ceramics were measured as a function of temperature ($25^{\circ}C\;{\sim}\;250^{\circ}C$). The dielectric constant, the loss, and the pyroelectric coefficient could be improved with the addition of small amounts of $ZrO_2$ up to 0.2 mol%. The dielectric and pyroelectric peak temperature are slightly shifted to lower temperatrues with the addition of amount of $ZrO_2$.