• 한국세라믹학회지
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• 제39권5호
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• pp.438-445
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• 2002

본 연구에서는 $PbO-TiO_2-SiO_2-BaO-ZnO-Al_2O_3-CaO-B_2O_3-Bi_2O_3-MgO$계의 유리를 $1,400{\circ}C$에서 용융시킨 후, 급랭, 분쇄하여 glass frit을 제조하였다. Glass frit 분말을 일축가압성형한 후 $750~1,000{\circ}C$의 온도범위에서 2시간 동안 소성 및 결정화 하였다. Glass frit의 결정화는 $750{\circ}$ 전후의 온도에서 시작되었고, 저온에서의 주된 결정상은 $Al_2O_3$와 hexagonal celsian($BaAl_2Si_2O_8$)이었다. 소성온도가 높아지면서 monoclinic celsian, $ZnAl_2O_4,\;Zn_2SiO_4,\;CaTi(SiO_4)O,\;TiO_24 등이 주된 결정상으로 나타났고, 특히 celsian은 hexagonal에서 monoclinic으로 상전이가 발생하였다. 그리고 15wt%의 PbO를 첨가한 glass frit에만 $PbTiO_3-CaTiO_3$ 고용체가 나타났다. 1MHz 대역에서 유전특성을 살펴본 결과 유전상수는 11~16이었고, 유전손실은 0.020 미만이었다. 그러나 15wt%의 PbO를 첨가한 glass frit의 경우는 $PbTiO_3-CaTiO_3$ 고용체 결정상의 존재로 유전상수가 17~26으로 높았고, 유전손실은 0.010~0.015로서 다른 조성들에 비하여 우수한 특성을 나타내었다.

• 대한화학회지
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• 제44권4호
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• pp.350-355
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• 2000

알루미늄 보레이트 화합물, $CaAl_2(BO_3)_2O$와 $BaAl_2(BO_3)_2O$은 매우 효과적으로 $Eu^{2+}$ 이온의 형광성을 나타내는 발광격자를 가지고 있다. 발광피크는 $Eu^{2+}$:$CaAl_2(BO_3)_2O$화합물에 있어서 450㎚이고 $Eu^{2+}$:$SrAl_2(BO_3)_2O$화합물에 있어서411㎚이며 $Eu^{2+}$:$BaAl_2(BO_3)_2O$ 화합물에 있어서 375㎚이다. 그러므로 $Eu^{2+}$:$CaAl_2(BO_3)_2O$ 화합물은 파란색을 내는 좋은 형광체이며, 특별히, 진공자외선 제논 플라마스 램프에 있어서 우수한 형광물질로 기대된다. $Eu^{2+}$ 이온은 PDP 형광체로써 관심이 높으며, Stokes shift는 형광물질의 도핑격자 크기에 의해서 결정이 된다. Stokes shift는 발광 파장을 결정하는 하나의 중요한 요소이다. 만일, 도핑격자의 크기가작아짐에 따라 $Eu^{2+}$ 이온의 5d 에너지 준위가 낮아지면, 발광 파장은 길어지고 Stokes shift크기는 커진다. 그러므로 결정격자의 크기를 측정하면 $Eu^{2+}$ 이온의 Stokes shift와 5d 에너지 준위 등의 발광성질을 예측할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1148-1151
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• 2002

Dielectric ceramics with nominal composition of $(Ba_{0.93}Sr_{0.07}O)-0.5Sm_2O_3-4.5TiO_2$ was prepared using the conventional mixed oxide process-derived powder. Effect of $SiO_2$, $MnO_2$ and $Al_2O_3$ impurity addition on the microwave properties was examined in some detail. Measured relative permittivity $(\varepsilon_r)$ values were in the range of 53 to 59 and showed little dependence on impurity addition. In contrast, quality factor $(Q{\cdot}f)$ and temperature coefficient of resonant frequency $(\tau_f)$ values were greatly influenced by the type and the amount of impurities. It was found that 0.1~0.2wt% addition of $Al_2O_3$ was most effective for improving the properties, where ${\varepsilon}_r$, $Q{\cdot}f$ and $\tau_f$ values were 57.7, 10000, and +7ppm/$^{\circ}C$, respectively.

• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1679-1683
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• 2018

Polycrystalline $BaSrCo_2(Fe_{1-x}Al_x)_{12}O_{22}$ (x = 0.00, 0.01, 0.05, and 0.10) samples were synthesized by polymerizable complex method. Based on the Rietveld refinement, crystal structures of the samples were found to be single-phased and determined to be rhombohedral with space group of R-3m. The hysteresis curves of the samples were measured under 15 kOe at various temperatures ranging from 4.2 and 295 K. It shows that they were not saturated with increasing Al ion contents due to the reduction of magnetic anisotropy. $M_{15kOe}$ was decreased with increasing Al ions contents. We expect that non-magnetic Al ions preferentially occupy the up-spin site of $18h_{VI}$, $3b_{VI}$, and $3a_{VI}$. The $M{\ddot{o}}ssbauer$ spectra of the samples were obtained at 295 K, and analyzed with sixsextets for Fe sites corresponding to the Y-type hexaferrite crystallography sites. The <$E_Q$> shows abrupt changes, and the <$H_{hf}$> shows abrupt decreases around x = 0.05 due to the coexistence of magnetic secondary phases.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.814-817
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• 2003

The sintering behavior of $BaO-B_{2}O_{3}-ZnO$, which is Pb-free glass-ceramic system, was examined as functions of the composition and the amount and particle size of $Al_{2}O_{3}$ filler. Different kinds of modifiers were added and $Al_{2}O_{3}$ fillers with different particle sizes ($1.5{\mu}m$ and $4.5{\mu}m$) were added. The glass frit-filler composites were sintered in the temperature range $520{\sim}580^{\circ}C$. X-ray diffraction results revealed that some of the composites crystallized during sintering. Dielectric constant and thermal expansion coefficient the glass-ceramics were analyzed.

• 한국결정성장학회지
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• 제8권4호
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• pp.626-633
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• 1998

본 연구에서는 고유전율의 저온소성용 글라스/세라믹을 제조하고자, SiO2-TiO2-RO계 결정화 유리를 제조하고 Al2O3를 필러 물질로 혼합하여 복합체를 제조하고 그 특성을 관찰하였다. 본 유리조성으로써 $900^{\circ}C$ 이하에서 결정화되는 유리의 제조가 가능하였고, RO (BaO, CaO, SrO)의 성분에 따라 결정화 온도는 변화함을 알 수 있었다. 본 유리조성에 $Bi_2O_3$를 플럭스로 첨가하고, 세라믹 필러로써 Al2O3를 사용하여 $860^{\circ}C$에서 소성함으로써 고유전율의 저온소성용 글라스/세라믹의 제조가 가능하였고, 이때 복합체의 밀도는 3.96g/$\textrm{cm}^3$ 이었고, 유전율은 17, Q.f 값은 600이었다.

• 한국세라믹학회지
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• 제35권2호
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• pp.151-162
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• 1998

ZnO-BaO-$SiO_2-Al_2O_3$계 유리 및 결정화 유리 시편들을 제조하여 평판형 고체산화물 연료전지 봉착재로의 이용가능성을 조사하였다 구성층과 일치되는 열팽창 계수 및 화학적 안정성을 봉착재로의 적용에 있어 판단 기준으로 정하였다 실험된 다양한 조성의 유리 및 결정화 유리 시편들중 7.79ZnO-58.52BaO-$28.69SiO_2-5Al_2O_3$(ZBS3-A5) 결정화 유리의 측정된 열팽창 계수값은 $11.02\times10^{-6/^{\circ}C}$로써 YSZ 및 LSC의 평균 열팽창 계수 값과의 차이가 $0.07\timestimes10^{-6/^{\circ}C}$로 매우 작아 봉착시 열응력 발생의 최소화를 기대할수 있었다 이런 ZBS3-A5+LSC 접합 couple의 경우는 ZnCr2O4 의 dis-crete한 입자가 결정화 유리 부위에 형성되었고 역시 시간의 증가에 따라 이러한 입자의 성장은 없었다 특히 ZBS3-A5 구성 성분인 Ba, Zn, Sil 그리고 Al의 YSZ 및 LSC로의 확산은 없어 봉착후에 YSZ 및 LSC의 전기적 특성에 악영향을 미치지 않으리라 판단되었다.

• 한국세라믹학회지
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• 제30권6호
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• pp.499-509
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• 1993

Structures of hematite(${\alpha}$-Fe2O3), Ba-ferrite(BaFe12O19) and Zn2Y(Ba2Zn2Fe12O22) were studied by powder X-ray diffraction(XRD) method. Powder XRD patterns of the ferrites were analyzed with the Rietveld method, and the final refined R-factors were RWP<0.01 and RI<0.03. The lattice parameters refined with hexagonal crystal system were a=5.0342${\AA}$, c=13.746${\AA}$ for hematite, a=5.8928${\AA}$, c=23.201${\AA}$ for Ba-ferrite, and a=5.8763${\AA}$, c=43.567${\AA}$ for Zn2Y. In the hematite, the oxygen parameter is 0.3072 and the Fe-O distances in FeO6octahedron are 1.941${\AA}$ and 2.118${\AA}$, close to the single crystal data of Blake et al.. In the Ba-ferrite, the Fe atom in oxygen trigonal bipyramid is displaced 0.155${\AA}$ away from the BaO3 mirror plane into 4e position. In the Zn2Y, 75% of Zn is located at the oxygen terahedral site in S-block.

• 한국세라믹학회지
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• 제48권1호
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• pp.40-45
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• 2011

In this study, the composition of optical glass for GMP(glass molding process) was designed with 'Design of Experiments' method. All the composition batch was performed by 'Create Factorial Design' method. Particularly, $SiO_2$, BaO and $Al_2O_3$ were chosen major parameters for investigating the effects of components on optical and thermal properties. BaO and $Al_2O_3$ strongly influenced on optical and thermal properties, respectively. Finally, the approximate values of desired optical and thermal values were obtained by microtuning of compositions. At the composition of $BaO:Al_2O_3:SiO_2$=10:4:48 (molar ratio), refractive index($n_d$) was 1.5833, coefficient of thermal expansion(CTE) was $104{\times}10^{-7}/^{\circ}C$.

• 한국세라믹학회지
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• 제24권4호
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• pp.321-328
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• 1987

The chemical durability of six alumino fluorophosphate glass samples studied. The composition of glass varied with MgF2 content from 0 to 12.5wt% in 30AlF3-2MgF2-(50-x)MF2-10P2O5(M; Sr, Ba). Samples were maintained in distilled water at 95$^{\circ}C$ from 1 to 100hrs. Weight loss, pH change and leached elements of the solution, and IR transmittance of samples were measured and also their surfaces were observed by SEM. Chemical durabilities of these samples were increased with increasing MgF2 contents. The following various properties were increased rapidly up to 10 hours after that changed slowly. The sample after leached at 95$^{\circ}C$ during 100 hrs showed 0.5mg/$\textrm{cm}^2$ in weight loss. The pH of leached solution is 6.2 and concentration of Mg, Sr, and Ba element of that leached solution were 24,115 and 125 ppm, respectively. The infrared transmittance of leached sample decreased 7% compare to unleached one. And also SEM photomicrograph and EDS analysis showed that the corrosion of samples were decreased with respect to increasing MgF2 content.