• 한국결정성장학회지
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• 제11권6호
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• pp.269-273
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• 2001

MgO를 기질로 한 세라믹스 시편에 $TiO_2$를 소량 첨가하고 $1450^{\circ}C$에서 열처리한 후 $TiO_2$를 첨가한 MgO 세라믹스의 수분에 대한 수화 반응에 미치는 영향을 조사하였다. $TiO_2$를 첨가하지 않은 MgO 세라믹스는 수분에 대한 수화반응에 의한 $Mg(OH)_2$의 생성으로 인한 질량변화가 관찰되었으나, $TiO_2$를 첨가함 MgO 세라믹스는 수분첩촉시간에 따른 질량변화가 관찰되지 않았다. $TiO_2$를 첨가한 MgO 세라믹스를 $1450^{\circ}C$에서 열처리했을 때, $Mg_2TiO_4$ 상이 관찰되었으며 특히 TiO$_2$를 첨가함에 따라 부피비중은 첨가량에 비례하며 증가한 반면에 가공율과 흡수율은 감소하는 경향을 나타내었다. 따라서 MgO 를 기질로 한 세라믹스에 $TiO_2$를 소량 첨가한 경우 표면에서 발생하는 수화 반응에 대하여 높은 저항성을 가짐을 확인하였다.

• 한국세라믹학회지
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• 제31권6호
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• pp.651-659
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• 1994

BaTiO3 ceramics were sintered on Al2O3, MgAl2O4, MgO and Mg-, Ca-, Y-stabilized zirconia setters. Then the influence of setters on the microstructure of BaTiO3 ceramics and the stability of setters were investigated by SEM, EDAX and XRD analyses. The microstructure of BaTiO3 ceramics sintered on Al2O3, MgAl2O4, MgO and Mg-PSZ showed large grain growth, but little grain growth on Ce-TZP(Tetragonal Zirconia Policrystal). Mg-PSZ(Partially Stabilized Zirconia), Ca-PSZ, Ce-TZP setters showed extensive phase transformation. Y-TZP and fused Y-SZ (Stabilized Zirconia) setters were stable. The liquid sintering aids of BaTiO3 ceramics accelerate mass transport. The reaction of SrTiO3 in BaTiO3 with ZrO2 resulted in the formation of SrZrO3.

• 한국세라믹학회지
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• 제35권4호
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• pp.347-354
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• 1998

Densification and grain growth behaviors of ITO ceramics were investigated as a function of TiO2 ad-ditions. TiO2 addition led to inhibition of the grain growth and promotion of the densification of ITO ceram-ics. From the microstructure observation it was found that the crack-like voids which were formed in pure ITO specimens decreased with increase of TiO2 additon. The grain growth exponent(n) was measur-ed to be 4 for pure ITO 3 for TiO2-doped ITO specimens respectively. It was supposed that the grain boun-dary migration of pure ITO ceramics was controlled by the pores which were moved by surface diffusion. On the contrary the grain boundary migration of TiO2-doped ITO specimens was depressed by solute drag effect. The activation energies for grain growth were measured to be 1013 kJ/mol for pure ITO ceramics and 460kJ/mol for TiO2-doped ITO specimens respectively.

• 한국세라믹학회지
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• 제56권4호
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• pp.374-386
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• 2019

A process for nitrogen doping of TiO₂ ceramics was developed, whereby polycrystalline titania particles were prepared at 450-1000℃ with variation of the firing schedule under N₂ atmosphere. The effect of nitrogen doping on the polycrystallites was investigated by X-ray diffraction (XRD) and Raman analysis. The microstructure of the TiO₂ ceramics changed with variation of the firing temperature and the firing atmosphere (N₂ or O₂). The microstructural changes in the nitrogen-doped TiO₂ ceramics were closely related to changes in the Raman spectra. Within the evaluated temperature range, the nitrogen-doped titania ceramics comprised anatase and/or rutile phases, similar to those of titania ceramics fired in air. Infiltration of nitrogen gas into the titania ceramics was analyzed by Raman spectroscopy and XRD analysis, showing a considerable change in the profiles of the N₂-doped TiO₂ ceramics compared with those of the TiO₂ ceramics fired under O₂ atmosphere. The nitrogen doping in the anatase phase may produce active sites for photocatalysis in the visible and ultraviolet regions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.402-405
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• 2001

The BaTiO$_3$+10wt%Nb$_2$O$_{5}$ ceramics were prepared by conventional mixed oxide method. The structural and dielectric properties of the BaTiO$_3$+10wt%Nb$_2$O$_{5}$ ceramics with the sintering temperature were investigated. Increasing the sintering temperature, the 2$\theta$ value of BaTiO$_3$peaks were shifted to the higher degree and intensity of the BaTiO$_3$and BaNbO$_3$peaks were increased. In the BaTiO$_3$+10wt%Nb$_2$O$_{5}$ ceramics sintered at 135$0^{\circ}C$ and 1375$^{\circ}C$, the grain was fine and uniform. Increasing the sintering temperature, the pore was decreased and the dielectric constant was increased. In the BaTiO$_3$+10wt%Nb$_2$O$_{5}$ ceramics sintered at 1375$^{\circ}C$, the dielectric constant and dielectric loss were 5424, 0.02 respectively.ctively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1541-1543
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• 2003

The microwave dielectric properties of $0.6Mg_4Ta_2O_9-0.4TiO_2$ ceramics were investigated. All sample of $0.6Mg_4Ta_2O_9-0.4TiO_2$ ceramics were prepared by the conventional mixed oxide method, and sintered in the temperature of $1350^{\circ}C{\sim}1450^{\circ}C$. The structural properties of $0.6Mg_4Ta_2O_9-0.4TiO_2$ ceramics were investigated by the X-ray diffraction meter. According to the X-ray diffraction patterns of $0.6Mg_4Ta_2O_9-0.4TiO_2$ ceramics, the major phase of the hexagonal $0.6Mg_4Ta_2O_9-0.4TiO_2$ were presented, In the case of $0.6Mg_4Ta_2O_9-0.4TiO_2$ ceramics sintered at $1400^{\circ}C$ for 5hr., the dielectric constant, quality factor and temperature coefficient of resonant frequency were 12.19, 109.411GHz, -17.21ppm/$^{\circ}C$, respectively.

• 한국통신학회논문지
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• 제18권8호
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• pp.1102-1107
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• 1993

CaO-TiO2 이성분계에서 40~50 mol% CaO 조성범위를 선택하여 CaTiO3과 CaTiO3-TiO2세라믹스의 마이크로파 유전특성을 조사하였다. CaTiO3 단일상 (50 mol% CaO조성)일 때 유전율(er) 178, 공진주파수 (fo)의 온도계수(r,)+1000ppm/C, 픔질계수인 Q값 2760(fo=2.7 GHz)으로 가장 큰 값을 나타내었다. CaTiO3와 TiO2상이 혼합상으로 있는 유전체에서는 CaO 함량이 감소함에 따라서 유전율과 공진주파수의 온도계수는 점차 감소하였으나 Q값과 밀도는 47 mol% CaO조성에서 가장 낮았다. 이것은 이상 혼합 세라믹에서 TiO2상의 감소로 인해 CaTiO3의 결정립 성장이 급속하게 일어남으로써 입계와 입내에 큰 기공이 존재하지 때문으로 생각된다.

• 전기학회논문지
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• 제56권4호
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• pp.756-760
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• 2007

The $(1-x)Mg_4Ta_2O_9-xwt%TiO_2\;(x=5\sim20)$ microwave dielectric ceramics were prepared by solid-state reaction method and sintered at $1450^{\circ}C$. According to the X-ray diffraction data, the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics had main phase of $Mg_4Ta_2O_9$ and $MgTi_2O_5$ peaks were added by increasing of $TiO_2$ addition. Microwave dielectric properties of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics were influenced by $MgTi_2O_5$ phase and properties of $TiO_2$. There was a little decrement of the quality factor from 116,800GHz of pure $Mg_4Ta_2O_9$ to 100,100GHz of 15wt% $TiO_2$ added one. But there was excellent improvement in temperature coefficient of the resonant frequency (TCRF) by addition of 15wt% $TiO_2$. The dielectric constant quality factor and TCRF of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics sintered at $1450^{\circ}C$ were $13.08\sim16.41,\;45,000\sim165,410GHz,\;-24.82\sim+3.88ppm/^{\circ}C$, respectively, depending on the value of x. Simulated dielectric resonator (DR) with $Mg_4Ta_2O_9-15wt%TiO_2$ ceramics had the operating frequency of 11.97GHz and $S_{2,1}$ of -35.034dB.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권7호
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• pp.344-348
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• 2006

The effect of x on microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics for microwave components were investigated. All spcecimens prepared by the conventional mixed oxied method and sintered at $1450^{\circ}C$. Microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-xTiO_2$ ceramics were influenced by $MgTi_2O_5$ phase. Also the microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were dominated with an addition of $CaTiO_3\;and\;SrTiO_3$. The dielectric constant $(\varepsilon_r)$, quality factor $(Q{\times}f_r)$ and temperature coefficient of the resonant frequency $(TCRF,\;\tau_f)$ of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were $12.96\sim70.98,\;5,132\sim186,410GHZ$ and $-35.82\sim+75.96ppm/^{\circ}C$, respectively, and depend on x and addition materials.

• 한국세라믹학회지
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• 제41권6호
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• pp.444-449
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• 2004

BaO-Nd$_2$O$_3$-TiO$_2$계 마이크로파 유전체 세라믹스에 결정화유리를 첨가하여 세라믹-결정화유리 복합체 유전재료를 제작하여, 적층 일체형 RF수동소자 모듈 구현을 위한 저온소결 유전재료로서의 응용가능성에 대해 검토하였다. BaO-Nd$_2$O$_3$-TiO$_2$계 유전체 세라믹스에 PbO-TiO$_2$-Al$_2$O$_3$-SiO$_2$ 조성의 결정화 유리를 5∼30 wt% 범위로 첨가하여 소결온도를 130$0^{\circ}C$에서 105$0^{\circ}C$까지 낮출 수 있었으며, 첨가량의 증가에 따라 유리의 연화로 인한 소결밀도의 증가 및 입성장이 뚜렷하게 관찰되었다. 특히, 결정화 유리를 20 wt% 이상 첨가하였을 경우, 105$0^{\circ}C$의 소결온도에서 95% 이상의 상대밀도를 갖는 양호한 소결체를 얻을 수 있었고, 이 때 유전을($\varepsilon$$_{r}$)은 72, 품질계수(Q-f)는 1500이었고, 공진주파수 온도계수($ au$$_{f}$)는 22ppm/$^{\circ}C$을 나타내었다. 이러한 높은 유전율은 유리속의 결정상 PbTiO$_3$의 존재에 기인한 것이다.