• 한국재료학회지
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• 제12권3호
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• pp.220-224
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• 2002

The oxide scales formed on $Ni_3Al$-7.8%Cr-1.3%Zr-0.8%Mo-0.025%B after oxidation at 900, 1000 and 110$0^{\circ}C$ in air were studied using XRD, SEM, EPMA and TEM. The oxide scales consisted primarily of $NiO,\; NiAl_2O_4,\;{\alpha}-Al_2O_3,\; monoclinic-ZrO_2,\; and \;tetragonal-ZrO_2$. The outer layer of the oxide scale was rich in Ni-oxides, whereas the internal oxide stringers were rich in Al-oxides and $ZrO_2$. Within the above oxide scales, Cr and Mo tended to exist as dissolved ions.

• 한국세라믹학회지
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• 제34권3호
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• pp.330-336
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• 1997

1:1 복합 페로스카이트 물질인 La(Mg1/2Ti1/2)O3 and La(Mg1/2Zr1/2)O3의 양이온 규칙 존재와 고주파 유전특성을 x선 회절과 회로망분석기를 사용하여 조사하였다. 기존의 연구에서는 두 물질 모두 양이온 규칙이 없으며 입방정 구조를 갖는다고 보고되었지만, 본 연구에서의 x선 분석에서는 양이온 규칙을 나타내는 초격자회절선과 비입방정 구조를 의미하는 기본회절선의 split이 발견되었다. 고주파 영역에서의 유전율은 La(Mg1/2Ti1/2)O3의 경우 29,La(Mg1/2Zr1/2)O3는 24, 품질계수(Q*f)는 각각 73000, 49000이다. 공진주파수 온도계수는 La(Mg1/2Ti1/2)O3의 경우 - 65ppm/$^{\circ}$C,La(Mg1/2Zr1/2)O3는 -80ppm/$^{\circ}$C로 음의 값을 가진다.

• 한국재료학회지
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• 제5권7호
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• pp.888-896
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• 1995

Al 금속분말을 zircon sand (ZrSiO$_4$)와 A1$_2$O$_3$혼합체에 첨가하여 반응소결시킴으로써 무수축 Mullite-ZrO$_2$, 요업체를 얻고자 하였다. 반응식, 3(Al+Al$_2$O$_3$)+2ZrSiO$_4$$\longrightarrow$3A1$_2$O$_3$ .2SiO$_2$+2ZrO$_2$에 의하여 ZrO$_2$-강화 Mullite 요업체를 제조하였다. Al 분말은 A1$_2$O$_3$에 대해 0-30 무게 퍼센트까지 대체하였다. 평량한 분말을 볼밀하여 혼합 분쇄한 후, 정수압 성형하여 시편을 제조하고, 온도범위 1450-1$600^{\circ}C$에서 3시간 반응소결시켰다. Al의 충분한 산화를 위해, 한편으로는 125$0^{\circ}C$에서 5시간동안 열처리를 거친후 소성온도로 올리기도 했다. Al을 첨가함으로서 반응은 촉진되었으며, 소성수축도 산화한 Al의 부피팽창에 의해 상쇄되어, 무수축요업체 제조의 가능성을 보였다. 박편모양을 한 비교적 큰 Al분말이 잘 분쇄되지 않음으로 해서, Al이 자리했던 곳에 큰 기공을 남겼다.

• 한국세라믹학회지
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• 제30권8호
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• pp.635-642
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• 1993

To obtain a higher dielectric constant material, we investigated Ca substitution for Pb in PbZrO3. In this study, the four mixtures of (Pb0.68Ca0.32)ZrO3, (Pb0.65Ca0.37)ZrO3, (Pb0.63Ca0.37)ZrO3, and (Pb0.60Ca0.40)ZrO3 were prepared by coprecipitation reaction of Pb(NO3)2, ZrOCl2, and CaCl2 with (NH4)2CO3 and NH4OH in aqueous solution. The (Pb1-xCax)ZrO3 with different x mole fractions (x=0.35, 0.37) showed not only high dielectric constant, but also high Q values and low temperature coefficient of the capacitance.

• E2M - 전기 전자와 첨단 소재
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• 제6권3호
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• pp.241-247
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• 1993

본 연구에서는 투광성 0.085Ba(L $a_{1}$2/N $b_{1}$2/) $O_{3}$- 0.915Pb(Z $r_{y}$ $Ti_{1-y}$) $O_{3}$(0.45.leq.y.leq.0.70)세라믹을 2단 소성법으로 제작한 후, PbZr $O_{3}$조성 및 온도에 따른 구조적, 강유전적특성을 측정하였다. XRD측정 결과, PbZr $O_{3}$조성이 감소할수록 결자상수 및 단위격자 체적은 감소하였으며 시편의 결정구조는 입방정계에서 능면체정계, 정방정계로 변화되었다. 8.5/60/40시편의 경우 포화분극, 잔류분극 및 항전계가 각각 33.28[.mu.C/$cm^{2}$], 4.15[kV/cm]로 전형적인 메모리 특성을 나타내었으며 PbZr $O_{3}$조성이 증가함에 따라 강유전 이력곡선은 slim loop특성을 나타내었다. 잔류분극은 온도가 증가함에 따라 감소하였으며 특히 PE-FE상경계 부근에 위치한 조성의 경우, 상전이 온도 이하의 온도에서 급격히 감소하는 경향을 나타내었다.다.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.349-355
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• 2002

The ionic conductivity of cubic solid solutions in the systems of CaO-$ZrO_2$, $Y_2O_3-ZrO_2$ prepared by SHS was examined. The higher conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Conductivity-temperature data was obtained at 1000 $^{\circ}C$ in atmosphere of low oxygen partial pressure (~$10^{-40}$ atm) for $Y_2O_3-ZrO_2$ cubic solid solutions. The data indicated that these materials could be reduced, and the decree of reduction would be related with the measuring electric field.

• 한국세라믹학회지
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• 제31권7호
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• pp.772-776
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• 1994

Using two kinds of ZrO2 powder stabilized by 8 mol% and 3 mol% of Y2O3 several microstructures were designed; two single composition specimens of 8 mol% Y2O3-ZrO3 and 3 mol% Y2O3-ZrO2 and five mixture specimens with multi-layered structure and particulate mixture structure at a mixing ratio of 1:1 by weight. Electrical conductivities were measured from 250 to 75$0^{\circ}C$ in air using an impedance analyser, and fracture toughness at room temperature using the indentation method. Making the mixture structures was more effective in enhancing fracture toughness than electrical conductivity. At low temperatures 3 mol% Y2O3-ZrO2 showed the highest values in both electrical conductivity and fracture toughness, while at high temperature the specimens of alternately stacked planar and coarse granulated structure were most favorable.

• 한국세라믹학회지
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• 제34권6호
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• pp.569-576
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• 1997

Electrically-induced strain and polarization studies of the (1-x)Pb(Mg1/3Nb2/3)O3-PbZrO3 crystalline solutions have been done. Dielectric constants with temperature were investigated for 0$\leq$x$\leq$0.95. With increasing PbZrO3 content the transition maxima were found to move to higher temperature region and DPT (Diffused Phase Transition) properties were decreased for x$\leq$0.60. Phase transition between ferroelectric states and antiferroelectric states was confirmed for 0.93$\times$10-3 for 0.4

• 한국세라믹학회지
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• 제31권9호
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• pp.969-974
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• 1994

After adding 8Y-ZrO2 powders to 3Y-ZrO2 powders at ratios of 0, 33, 50, 67, and 100% by weight, the mixed yttria-stabilized zirconia specimens were fabricated into thin plate using tape~casting method and then sintered at 150$0^{\circ}C$ for 4h in air. The crystalline structure, microstructure and electrical properties of the sintered zirconia thin plates were investigated by using X-ray diffractometer, scanning electron microscope and impedance analyser, respectively. At the temperatures higher than 75$0^{\circ}C$, the sintered thin plate with 33% 8Y-ZrO2 content shows higher mechanical properties and lower electrical resistivity than 8Y-ZrO2 thin plate which is generally used as an electrolyte for solid oxide fuel cells. This is due to the fact that the zirconia thin plates with low 8Y-ZrO2 content maintain the slope of low temperature region up to high temperatures, whereas at temperatures higher than 50$0^{\circ}C$ the slope decrease in the zirconia thin plates with high 8Y-ZrO2 content.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.853-855
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• 1998

The electrical resistivity and mechanical properties of the hot-pressed and annealed ${\beta}$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_{3}$(6:4wt%). In this microstructures. no reactions were observed between $\beta$-SiC and $ZrB_2$, and the relative density is over 97.6% of the theoretical density. Phase analysis of composites by XRD revealed mostly of a $\alpha$-SiC(6H, 4H), $ZrB_2$ and weakly $\beta$-SiC(15R) phase. The fracture toughness decreased with increased $Al_{2}O_{3}+Y_{2}O_{3}$ contents and showed the highest for composite added with 4wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives. The electrical resistivity increased with increased $Al_{2}O_{3}+Y_{2}O_{3}$ contents because of the increasing tendency of pore formation according to amount of liquid forming additives $Al_{2}O_{3}+Y_{2}O_{3}$. The electrical resistivity of composites is all positive temperature coefficient resistance(PTCR) against temperature up to $700^{\circ}C$.