• 한국세라믹학회지
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• 제34권6호
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• pp.583-590
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• 1997

The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.

• 한국세라믹학회지
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• 제36권10호
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• pp.1108-1114
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• 1999

Microstructure and electrical properties of ZnO-doped (0-5 mol%) 0.05 Pb(Mn1/3Sb2/3)O3-0.95 PZT ceramics were investigated. Sintering temperature was decreased to 100$0^{\circ}C$ due to eutetic reaction between PbO and ZnO. Grain-size increased up to adding 1mol% ZnO and then decreased. Compositions of grain and grain-boundary were investigated by WDS. Lattice parameter was decreased with ZnO addition. Density increased with ZnO addition and reached to the maximum of 7.84(g/cm2) at 2 mol% ZnO. The effect of ZnO on electrical properties of PMS-PZT was investigated. At 3mol% ZnO addition electromechanical coupling factor(kp) was about 50% and relative dielectric constant($\varepsilon$33/$\varepsilon$0) was 997 Mechanical quality factor(Qm) decreased with ZnO addition. Lattice parameters and tetragonality(c/a) were measured to investigate relationship between the electric properties and substitution of Zn2+. At 3 mol% ZnO tetragonality was maximiged at c/a=1.0035 Curie temperature (Tc) decreased slightly with ZnO addition.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.272-273
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• 2006

LTCC(low temperature co-fired ceramics)용 glass/ceramic 복합체를 제조하기 위해 4 종류의 borosilicate계 glass를 선정하고 filler로 $Al_2O_3$ ceramics를 filler 사용하여 30~50 vol% glass frit에 따른 소결 및 유전 특성에 대하여 조사하였다. Glass frit은 $SiO_2$와 $B_2O_3$ 함량비를 고정한 후 R(CaO, BaO, ZnO, $Bi_2O_3$)에 따라 유리 연화온도(Ts)와 함량이 소결에 미치는 영향 및 유전 특성 변화를 고찰한 결과, CaO-$B_2O_3-SiO_2$ glass의 경우 다량의 2 차상이 형성되었고, 이에 $900^{\circ}C$ 이하에서 완전 소결이 이루어지지 않았으며, BaO-$B_2O_3-SiO_2$ glass는 celsian($BaAl_2Si_2O_8$) 결정이 형성되면서 소결성의 저하를 갖고 왔으며, ZnO-$B_2O_3-SiO_2$ glass는 소결이 진행됨에 따라 주상이 $Al_2O_3$에서 gahnite($ZnAl_2O_4$) 결정이 형성되면서 품질계수가 크게 증가하였으며, $Bi_2O_3-B_2O_3-SiO_2$ glass는 45 vol%일 때 $900^{\circ}C$에서부터 일정한 선수축율 특성을 나타내었지만, 다량의 액상으로 인하여 유전 특성의 저하를 나타내었다.

• Journal of Ceramic Processing Research
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• 제13권spc1호
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• pp.37-41
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• 2012

A lithium ion conducting borosilicate glass was fabricated by a conventional melt quenching technique from a mixture of Li2CO3, B2O3 and SiO2 powders. The Li ion conductivity of the lithium borosilicate glasses was evaluated in terms of the SiO2/B2O3 ratio. In the Li2O-B2O3-SiO2 ternary glass, the glass forming region decreases with an increasing Li2O content. At the same Li2O, the crystallization tendency of the glass samples increases with the SiO2/B2O3 ratio, resulting in a reduced glass forming region in the Li2O-B2O3-SiO2 ternary glass. The electrical conductivity moderately depends on the SiO2/B2O3 ratio in the Li2O-B2O3-SiO2 ternary glass. The conductivity of the glasses slightly increases with the SiO2/B2O3 ratio. The observed phenomenon can be explained by the modification of the glass structure as a function of the SiO2 content.

• 한국세라믹학회지
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• 제37권11호
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• pp.1097-1104
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• 2000

MOD(Metal-Organic-Decomposition)법에 의해 $Y_2$O$_3$버퍼층에 Pt/TiO$_2$/SiO$_2$/Si 기판 위에 제조한 후, 그 표면 위에 졸-겔 방법으로 YMnO$_3$박막을 형성하였다. 기판의 종류와 수화조건 변화가 YMnO$_3$박막의 결정화 거동에 미치는 영향을 고찰하였으며, 또한 $Y_2$O$_3$버퍼층 유.무에 따른 Mn의 산화상태를 확인하고 이에 따른 유전특성 변화를 연구하였다. $Y_2$O$_3$버퍼층을 삽입하지 않고 직접 기판 위에 형성한 YMnO$_3$박막의 결정상은 기판의 종류 및 Rw 변화에 관계없이 orthorhombic 구조임이 확인되었다. 반면, $Y_2$O$_3$버퍼층 위에 형성된 YMnO$_3$박막의 경우에는 Rw($H_2O$/alkoxide mole ratio)가 0~6 범위 내에서 낮아질술고 hexagonal 결정상 성장에 유리하였으며, 또한 Pt(111)/TiO$_2$/SiO$_2$/Si 기판이 Ptd(200)/TiO$_2$/SiO$_2$/Si에 비하여 결정상 형성에 용이하였다. $Y_2$O$_3$버퍼층은 YMnO$_3$결정상 내에서 $Mn^{4+}$ 이온형성을 억제함으로써 누설전류밀도가 크게 감소되는 효과를 주었으며, 동시에 강유전 특성을 지닌 hexagonal 결정상 형성에 유리하게 작용하였다. 결론적으로, $Y_2$O$_3$는 Pt가 코팅된 Si 기판 위에 YMnO$_3$박막 제조시 그 강유전 특성을 향상시켜주는 우수한 버퍼층 재료임을 확인하였다.

• 한국재료학회지
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• 제11권12호
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• pp.1080-1085
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• 2001

Dielectric properties and leakage current characteristics of 100 nm-thick $Ta_2O_5/Al_2O_3$multilayer thin films, which were fabricated by reactive sputtering of$Al_2O_3$and$Ta_2O_5$ successively on top of each other for total 9 layers, have been investigated with variation of the$Al_2O_3$content$(i.e,\;Ta_2O_5/Al_2O_3 \;thickness\;ratio)$.$Ta_2O_5/Al_2O_3$films were amorphous regardless of the$Al_2O_3$content. With increasing the$Al_2O_3$content from 0% to 100%, refractive index of the $Ta_2O_5/Al_2O_3$films decreased linearly from 2.03 to 1.56 and dielectric constant was lowered from 23.9 to 7.7 Variation of the dielectric constant with the$Al_2O_3$content was in good agreement with the behavior that was obtained by assuming parallel capacitors of$Al_2O_3$and Ta_2O_5$. Leakage current characteristics of $Ta_2O_5/Al_2O_3$ multilayer films were superior to those of $Ta_2O_5$ and$Al_2O_3$films. $Ta_2O_5/Al_2O_3$ films of 5% and 10%$Al_2O_3$content exhibited excellent leakage current densities which were lower than $10^{-7} A/cm^2$ at 1MV/cm.

• 한국결정성장학회지
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• 제2권2호
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• pp.71-76
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• 1992

$0.05Pb(Al_{2/3}W_{1/3})O_3-0.95Pb(Zr_{0.52}Ti0.48)O_3$를 기본 조성으로 $MnO_2,Fe_2O_3$를 첨가제로 하여 사진식각법(Photolithography)을 이용 세라믹 필터를 제작하였다. $MnO_2$의 첨가량이 증가함에 따라 전기 기계 결합 계수(Kp)가 낮아지며, $Fe_2O_3$의 경우 Kp값은 57% 정도로 우수하나 기계적 품질 계수(Qm)는 $MnO_2$첨가의 경우에 비해 상대적으로 낮은 값을 보여주고 있다. $MnO_2$0.3wt% 첨가의 경우 3dB 대역폭은 155kHz, $ Fe_2O_3$0.1wt%인 경우 260kHz로써 Qmr값이 크기에 반비례하였으며, 군지연시간 특성은 $MnO_2$의 경우 Gaussian 특성을,$Fe_2O_3$의 경우 Butterworth 특성을 나타내었다.

• 한국세라믹학회지
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• 제34권1호
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• pp.102-108
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• 1997

수용성 ZrOCl2.8H2O, YCl3.6H2O 및 Ce(NO3)3.6H2O를 사용하여 공침법으로 다양한 조성의 Y2O3-CeO2-ZrO2 분말을 합성하고, 이들의 압분체를 1400, 150$0^{\circ}C$에서 2시간동안 공기 중에서 상압소결하였다. 2mol%Y2O3-ZrO2 조성의 140$0^{\circ}C$ 소결체는 강도(1003MPa)와 미세경도(12.6GPa) 면에서 제일 우수하였으나, 인성은 10mol%CeO2-ZrO2의 경우가 13.3MPa.m1/2로 제일 높았다. CeO2-ZrO2에Y2O3의 첨가는 소결체의 평균 결정입자의 크기를 감소시켰고, 이로 인하여 강도와 경도는 증가하지만 인성은 감소하였다. 반면에 Y2O3-ZrO3에 CeO2의 첨가는 수열분위기에서 장시간 저온시효동안 정방정상의 안정화를 향상시키는 효과를 나타내었다.

• 한국세라믹학회지
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• 제22권6호
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• pp.42-52
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• 1985

Several $Al_2O_3$-based polycrystalline which had different dopant ratio in the range of 0.5mol% were prepared by doping pure $Cr_2O_3$ $HfO_2$. Single crystalline which had same composition with above polycrystalline were made by means of floating zone method. This study examined the role of each dopant for enhancing the mechanical properties of $Al_2O_3$-based Ceramics. Optical micrographs $({ imes}200)$ of $Al_2O_3-Cr_2O_3$ single crystal showing not only radial crack (rc) on the specimen surface but median crack(mc) and lateral crack(lc) under surface at the edge of indentation mark. Fracture toughness of Al2O3-based Ceramics was increased with $ZrO_2$ content. Alloying effect of $Cr_2O_3$ contributed to the hardness of $Al_2O_3$ based ceramics.

• 한국세라믹학회지
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• 제29권9호
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• pp.719-728
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• 1992

ZrO2/Al2O3-Mullite composites were prepared by infiltration of the silica sol to the porous ZrO2/Al2O3 bodies. The porous ZrO2/Al2O3 bodies for infiltration were fabricated using ZrO2 (20wt%)/Al2O3 composite powders synthesized by the emulsion-hot kerosene drying method. The preparation of silica sols was conducted by the hydrolysis-peptization of an alcoholic TEOS solution. When ZrO2/Al2O3-Mullite and ZrO2/Al2O3 composites were sintered at 1$650^{\circ}C$ for 4 hrs, both of them showed an excellent sinterability. As the amount of mullite added in the composites increased, the ratio of the tetragonal phase of zirconia to the monoclinic phase at the room temperature became higher. It was known that values of the fracture toughness of the ZrO2/Al2O3-Mullite composites were about 5.48 MPa.m1/2 much larger than that of the ZrO2/Al2O3 system.