• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권11호
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• pp.550-554
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• 2001

$(Ba_{0.6}Sr_{0.4}Ca_x)TiO_3 + yAl_2O_3$ wt% (x=0.10, 0.15, 0.20, y=0~3.0) ceramics were fabricated by the mixed-oxide method, and their structural and dielectric properties were investigated with variation of composition ratio and $Al_2O_3$ doping content. As results of the X-ray diffraction and microstructure analysis, all BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with an increase of $Al_2O_3$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing $Al_2O_3$doping content. The dielectric loss is minimum at BSCT doped with 1.5wt% $Al_2O_3$content. The tunability was decreased with increasing an Ca content and the BSCT(50/40/10) specimen doped with 2.0wt% $Al_2O_3$content showed the maximum value of 4.2%.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.189-194
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• 1999

Crystallization of glasses in the system (Ca, Sr, Ba)$O-Al_2O_3-B_2O_3-SiO_2-TiO_2$ and dielectric properties of crystallized glasses were investigated. As increasing B2O3 content and decreasing SiO2 content in the glass, the major crystalline phase changed from $(Sr, Ba)_2TiSi_2O_8$ to (Ca, Sr, Ba)TiO3, the dielectric constant of crystallized glasses increased and the Temperature Coefficient of Capacitance (TCC) changed to negative. The dielectric constant and TCC was estimated for (Sr, Ba)2TiSi2O8 phase as 18 and -440 $ppm/^{\circ}C$, respectively and for (Ca, Sr, Ba)TiO3 phase as 307 and -1900 $ppm/^{\circ}C$, respectively. The dielectric properties of (Ca, Sr, Ba)TiO3 phase (in this study) were similar to those of (Ca, Ba) TiO_3 solid-solution^12)$, but $(Sr, Ba)_2TiSi_2O_8$ phase (in this study) and $Sr_2TiSi_2O_\;8^4$ showed the different properties.

• 한국안광학회지
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• 제8권1호
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• pp.7-10
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• 2003

4성분 $SrO-B_2O_3-Al_2O_3-SiO_2$ 유리들을 $R({\equiv}SrO\;mole%/B_2O_3\;mole%)$과 $K({\equiv}(Al_2O_3+SiO_2)\;mole%/B_2O_3\;mole%)$에 의하여 제작하여 적외선 흡수(Infrared absorption)을 이용하여 유리들의 구조를 조사하였다. R의 증가에 따라 $1,200{\sim}1,600cm^{-1}$ 영역에서 대칭적 3배위 구조인 $BO_3$ 단위구조에 의한 B-O 결합의 신축떨기(stretching vibration)에 의한 흡수 띠의 세기가 감소되어지며, 사면체 구조인 $BO_4$ 단위구조에 의한 B-O 결합의 신축떨기에 의한 흡수 띠의 세기는 $800{\sim}1,200cm^{-1}$ 영역에서 변화되어졌다. 그라고 K의 증가에 따라 대칭적 3배위 구조인 $BO_3$ 단위구조에 의한 B-O 결합의 신축떨기에 의한 흡수 띠의 세기는 증가되어지며, 사면체 구조인 $BO_4$ 단위구조에 의한 B-O 결합의 신축떨기에 의한 흡수 띠의 세기가 감소되어졌다.

• 대한화학회지
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• 제47권4호
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• pp.370-375
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• 2003

보라색 발광 다이오드에 의해 여기되어 청색, 녹색, 적색을 발광하는 형광체로 각각 $BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, ZnCdS:Ag,Cl 형광체를 선택하였다. 보라색 발광 다이오드의 발광에서 형광체에 의해서 완전히 흡수되지 않고 나오는 보라색 발광과 $BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, ZnCdS:Ag,Cl 형광체에서 나오는 청색, 녹색, 적색 발광을 조합하여 사파장 백색 발광 다이오드를 만들었다. 사파장 백색 발광 다이오드의 발광 특성을 확인하였다.

• 한국세라믹학회지
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• 제45권3호
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• pp.146-149
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• 2008

Strontium-substituted $Sr_{1-x}Ba_xAl_2O_4:Eu^{2+},\;Dy^{3+}$ compositions were prepared by the solid state synthesis method. These compositions were characterized for their phase, crystallinity and morphology using powder x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Photoluminescence properties were investigated by measuring excitation spectra, emission spectra and decay time for varying Ba/Sr concentrations. Photoluminescence results show higher luminescence and long decay time for $Sr_{1-x}Ba_xAl_2O_4:Eu^{2+},\;Dy^{3+}$(x=0). This is probably due to the influence of the 5d electron states of $Eu^{2+}$ in the crystal field. Long persistence was observed for these compositions due to $Dy^{3+}$ co-doping.

• 한국결정성장학회지
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• 제9권3호
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• pp.315-319
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• 1999

고상반응법으로 Eu와 Dy을 공부활제로 한$SrAl_2O_4$ 형광체 분말을 합성한 후, PL(Photoluminescence) 측정 장치를 이용하여 장잔광 축광재료소서 가장 중요한 발광특성과 장잔광특성을 조사하였다. 10K의 발광스펙트럼은 청색파장의 450nm(2.755 eV)와 녹색 파장의 520nm(2.384 eV)의 위치에서 뚜렷한 발광피크를 나타내었는데 반하여 300K에서는 450nm의 발광피크는 관측되지 않고 주로 520nm의 발광피크가 관측되었다. 그리고$SrAl_2O_4$:$Eu^{+2},Dy^{+3}$ 형광체의 잔광세기는 시간에 따라 지수 함수적으로 감소되나 발광의 감쇠속도가 작은 뛰어난 장잔광 특성을 나타내었다.

• 한국세라믹학회지
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• 제27권7호
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• pp.841-850
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• 1990

The electrical conductivity of SrTiO3 thick films, which has been prepared by screen printing and sintering on polycrystalline Al2O3 substrates, was determined as a function of oxygen partial pressure and temperature. The data showed that electrical conductivity was proportional to the -1/4th power of the oxygen partial pressure for the oxygen partial pressure range from 10-4-10-8 to 10-20 atm and proportional to Po2+1/4 for the oxygen partial pressure range from 10-6-10-4 to 1atm. And then n-p transition region of electrical conductivity moved to lower oxygen partial pressure region as the sintering temperature of thick film specimens increased under about 140$0^{\circ}C$. These data were consistent with the presence of small amounts of acceptor impurities in SrTiO3 thick film which have been diffused from Al2O3 substrate in the range of solid solubility limit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1493-1495
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• 2001

$(Ba_{0.6-x}Sr_{0.4}Ca_x)TiO_3+yAl_2O_3$ wt% (x=0.10, 0.15, 0.20, y=0.5 $\sim$ 3.0) specimens were fabricated by the mixed-oxide method and then the structural properties as a function of the composition ratio and $Al_2O_3$ contents were studied. All BSCT specimens showed dense and homogeneous structure without the presence of the seconds phase. The sintered density was decreased with increase ad $Al_2O_3$ content. The Curie temperature and dielectric constant at room temperature decreased with increasing $Al_2O_3$ content. The dielectric constant and dielectric loss of the doped-0.5 wt% $Al_2O_3$ BSCT(50/40/10) specimen were about 3131 and 0.932% at 1KHz, respectively.

• 한국전기전자재료학회논문지
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• 제25권8호
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• pp.616-619
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• 2012

Oxides possess several interesting properties, such as ferroelectricity, magnetism, superconductivity, and multiferroic behavior, which can effectively be used oxide electronics based on epitaxially grown heterostructures. The microscopic properties of oxide interfaces may have a strong impact on the electrical transport properties of these heterostructures. It was recently demonstrated that high electrical conductivity and mobility can be achieved in the system of an ultrathin $LaAlO_3$ film deposited on a $TiO_2$-terminated $SrTiO_3$ substrate, which was a remarkable result because the conducting layer was at the interface between two insulators. In this study, we observe that the current-voltage characteristics exhibit $LaAlO_3$ thickness dependence of electrical conductivity in $TiO_2$-terminated $SrTiO_3$. We find that the $LaAlO_3$ layers with a thickness of up 3 unit cells, result in highly insulating interfaces, whereas those with thickness of 4 unit cells and above result in conducting interfaces.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.52.1-52.1
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• 2000