• 한국결정성장학회지
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• 제8권3호
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• pp.493-497
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• 1998

부활제인 $Eu_2O_3$의 농도를 변화시킨 $Sr_{1-x}Eu_xAl_2O_4$(x=0.005~0.2mol%)계 장잔광 형광체를 98%Ar+2% H2의 환원분위기에서 고상반응시켜 합성한 후 X-선 회절실험과 장잔광 축광재료로서 가장 중요한 발광특성과 장잔광 특성을 조사하였다. $SrAl_2O_4:Eu^{2+}$계 형광체는 $Eu_2O_3$의 농도에 관계없이 녹황색의 520nm파장을 최대 발광파장으로 하는 발광스펙트럼을 나타내었으나, 발광특성을 크게 저해하지 않는 SrAl2O4의 단일상을 얻기 위한 농도는 0.05mol% 이하가 적절하였다. 또한 $SrAl_2O_4:Eu^{2+}$ 형광체의 잔광강도는 $Eu_2O_3$의 농도에 무관하게 시간에 따라 모든 시료에서 지수 함수적으로 감소하나, Eu2O3의 농도가 0.05mol% 이하인 경우에 발광의 감쇠속도가 작은 뛰어난 장잔광특성을 나타내었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.387-390
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• 2000

The $Al_2$O$_3$specimens were prepared by the conventional mixed oxide method with addition La$_2$O$_3$, Bi$_2$O$_3$. The specimens were sintered at 15$25^{\circ}C$, 5hr., in air. The structural properties of the specimens were investigated by XRD and SEM. The $Al_2$O$_3$ceramics with dopants had hexagonal structure and didn't show secondary phases. In the case of specimens with 0.25wt% La$_2$O$_3$and 0.25wt% Bi$_2$O$_3$bulk densities and lattice parameter of c/a were 3.818g/cm$^3$, 3.783g/cm$^3$and ca=2.725, c/a=2.723, respectively. The bulk densities of $Al_2$O$_3$ceramics were decreased with dopants.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.382-382
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• 2010

The etch characteristics of the $HfAlO_3$ thin films and selectivity of $HfAlO_3$ to $SiO_2$ in $Cl_2/BCl_3$/Ar plasma were investigated in this work. The maximum etch rate was 108.7 nm/min and selectivity of $HfAlO_3$ to $SiO_2$ was 1.11 at $Cl_2$(3sccm)/$BCl_3$(4sccm)/Ar(16sccm), RF power of 500 W, DC-bias voltage of - 100 V, process pressure of 1 Pa and substrate temperature of $40^{\circ}C$. As increasing RF power and DC-bias voltage, etch rates of the $HfAlO_3$ thin films increased. Whereas as decreasing of the process pressure, those of the $HfAlO_3$ thin films were increased. The chemical reaction on the surface of the etched the $HfAlO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS).

• 한국세라믹학회지
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• 제47권2호
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• pp.122-126
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• 2010

In this article photoluminescence of the $Al_2O_3:xCr_2O_3$ solid solutions prepared by solid state reaction method are represented. The effect of $Cr_2O_3$-activator concentration and heat treatment time on the PL characteristics have been discussed in conjunction with microstructure of phosphor samples. The $Al_2O_3:xCr_2O_3$ phosphors show the highest PL intensity at x=0.003 mole when the samples are reacted at $1600^{\circ}C$ for 5 h. The PL emission and absorption spectra show the maximum peaks at 698 nm and at 398 nm respectively. The CIE color coordinate is (x=0.646, y=0.316) at 0.003 mole $Cr_2O_3$, which value is very close to the NTSC coordinate of red color. This characteristic feature of $Al_2O_3:xCr_2O_3$ has been applied for an additive to improve the color characteristic of other red phosphor $LiEuW_2O_8$ which has a relatively poor color purity with an emission peak centered at 615 nm and with a CIE coordinate (x=0.530, y=0.280). The $Al_2O_3:0.003Cr_2O_3$ phosphor has been mixed with the $LiEuW_2O_8$ phosphor powder and the PL characteristics and CIE color coordinates are characterized. The $Al_2O_3:xCr_2O_3$ phosphor was found effective for improving the CRI (color rendering index) of $LiEuW_2O_8$ phosphor.

• 한국세라믹학회지
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• 제39권5호
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• pp.473-478
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• 2002

Flux법과 마이크로파 가열법으로 $Al_2(SO_4)_3+2Na_2SO_4$ 및 ${\gamma}-Al_2O_3+2Na_2SO_4$ 분말혼합물로부터 ${\alpha}-Al_2O_3$ 판상체(platelets)를 합성하였다. ${\alpha}-Al_2O_3$ 판상체 형성에 미치는 마이크로파의 영향을 조사하기 위하여 DTA-TG, XRD 및 SEM을 이용하였다. $Al_2(SO_4)_3+2Na_2SO_4$ 혼합물의 경우, 마이크로파로 가열된 시료는 재래식으로 가열된 시료에 비하여 입자의 크기가 작고 응집체로 구성된 ${\alpha}-Al_2O_3$ 판상체로 나타났다. ${\gamma}-Al_2O_3+2Na_2SO_4$ 혼합물의 경우, 마이크로파 가열에 의한 ${\alpha}-Al_2O_3$ 판상체 형성온도는 재래식 가열에 의한 형성온도 보다 낮았다. 또한 마이크로파로 가열된 시료의 형상은 재래식으로 가열된 시료의 형상과 유사하였다. 그러나 마이크로파로 가열된 시료는 재래식으로 가열된 시료에 비하여 입자의 크기가 작았다.

• Journal of Welding and Joining
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• 제10권4호
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• pp.213-221
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• 1992

Al$_{2}$O$_{3}$ ceramic coating layer by gas flame spraying was very porous, therefore it could not have wear and corrosion resistance at all. To get a dense and strong coating layer, a method to infiltrate an alloy into the pores of $Al_{2}$O$_{3}$ ceramic coating was investigated. Cu-Ti alloys, which had good wettability and reactivity with $Al_{2}$O$_{3}$ ceramic, were examined for infiltration. Infiltration of the alloys was performed in vacuum at 1100.deg.C. The melt of Cu-50 at % Ti alloy was well penetrated through the porous $Al_{2}$O$_{3}$ coating and tightly sealed the pores, unbounded area and microcracks in the coating. The alloy melt in the pores reacted with $Al_{2}$O$_{3}$ ceramic to produce a suboxide phase, Cu$_{2}$Ti$_{4}$O. This composite layer which was composed of $Al_{2}$O$_{3}$ and Cu$_{2}$Ti$_{4}$O phase had good microstructure and wear and corrosion resistance. Additionally, microstructures at interfaces between coating layers were greatly improved owing to the effect of vacuum heat treating.

• 한국재료학회지
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• 제23권10호
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• pp.574-579
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• 2013

The milling and particulate characteristics of Al alloy-$Al_2O_3$ powder mixtures for a reaction-bonded $Al_2O_3$ (RBAO) process were studied. A commercially available prealloyed Al powder with Zn, Mg, Cu and Cr alloying elements (7475 series) was mixed with a calcined sinter-active $Al_2O_3$ powder and then milled in centrifugal milling equipment for ~48 hrs. The Al alloy-$Al_2O_3$ powder mixtures after milling were characterized and evaluated in various ways to reveal their particulate characteristics during milling. The milling efficiency of the Al alloy increased with a longer milling time. Comminution of the Al alloy particles started with its elongation, showing a high aspect ratio. With a longer milling time, the elongated Al alloy particle changed in terms of its shape and size, becoming equiaxially fine particles. Regardless of the milling efficiency of the Al alloy particles, all of the Al alloy particles repeatedly experienced strong plastic deformation during milling, giving rise to higher density of surface defects, such as microcracks, and leading to higher residual microstress within the Al alloy particles. The chemical reactions, oxidation behavior and hydration behavior of the Al alloy particles and the hydrolysis characteristics of their reaction with the environment were also observed during the milling process and during the subsequent powder handling steps.

• 한국세라믹학회지
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• 제34권6호
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• pp.629-635
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• 1997

The effects of the annealing atmospheres(O2, N2) and sintering additives that Bi2O3 is a major composition on the microwave dielectric and sintering propertie of (1-x)CaTiO3-xLaAlO3 system were investigated. The annealing atmospheres and the increase of annealing time after sintering did not affect the relative dielectric constant($\varepsilon$r) and temperature coefficient of resonant frequency($\tau$f) of (1-x)CaTiO3-xLaAlO3 system. However, the Q.f0 values of (1-x)CaTiO3-xLaAlO3 were very sensitive to annealing atmospheres. As the annealing time increased under O2 atmosphere the Q.f0 values of (1-x)CaTiO3-xLaAlO3 enhanced untill 10 hrs in 0.3$\leq$x$\leq$0.6 region, but degraded over that time. The increasing rate of Q.f0 value increased wth increasing x. On the other hand, as the annealing time increased under N2 atmosphere the Q.f0 values were constant in x$\leq$0.6 region, increased gradually in x$\geq$0.7 region. When 0.97Bi2O3-0.03Al2O3 and 0.76Bi2O3-0.24NiO of 3wt% as sintering additives were added to (Ca0.5La0.5) (Ti0.5Al0.5)O3 (x=0.5) the sintering temperature of 1$600^{\circ}C$ was lowered to 140$0^{\circ}C$, and the relative dielectric constant($\varepsilon$r) and temperature coefficient of resonant frequency($\tau$f) were not nearly changed. The addition of 0.97Bi2O3-0.03Al2O3 and 0.76Bi2O3-0.24NiO of 3wt% to (Ca0.5La0.5)(Ti0.5Al0.5)O3 made the Q.f0 values to be lower about 15% and 34%, respectively.

• 한국진공학회지
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• 제9권4호
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• pp.411-418
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• 2000

DC 반응성 스퍼터링법을 이용하여 스퍼터링 가스내 산소함량을 30~70%의 범위에서 변화시키며 상온에서 300 nm 두께의 $Al_2O_3$ 박막을 제조하였다. 스퍼터링 가스내 산소함량 30~70%의 조건에서 모두 비정질 $Al_2O_3$ 박막이 성막되었으며, 스퍼터링 가스내 산소함량에 무관하게 1.58 정도의 굴절계수를 나타내었다. 스퍼터링 가스내 산소함량 50 % 이상의 조건으로 증착한 $Al_2O_3$ 박막은 550 nm 파장에서 98% 정도의 우수한 투과도를 나타내었으나, 산소함량 30% 및 40%의 조건에서는 투과도가 94% 정도로 저하하였다. 스퍼터링 가스내 산소함량 50%의 조건으로 성막한 $Al_2O_3$ 박막의 유전상수는 10.9, 손실계수는 0.01로 최적의 유전특성을 나타내었다. 스퍼터링 가스내 산소함량 40~60%의 조건으로 증착한 $Al_2O_3$박막은 C-V곡선에서 flatband 전압 $V_{FB}$의 이동이 발생하지 않았으며, 150 kV/cm에서 $10^{-5}\textrm{A/cm}^2$ 이하의 우수한 누설전류 특성을 나타내었다.

• 한국세라믹학회지
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• 제32권3호
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• pp.331-340
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• 1995

Microwave (Hybrid) Heating (MHH) was used to oxidize and sinter Al-Al2O3 powder mixture. For 25 v/o Al specimen and 35 v/o Al specimen, the total processing to produce low-shrinkage reaction bonded alumina was carried out within 1 hour even though conventional furnace process took more than 10 hours. Compared with conventional fast firing process, MHH process increased more than 40% oxidation at the same temperature, and these high oxidation rates were thought to be caused by the surface ohmic current on Al particles.