• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.350-353
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• 2003

Millimeter-wave dielectric ceramics have been used like applications for ultrahigh speed wireless LAN because it reduces the resources of electromagnetic wave, and Intelligent Transport System (ITS) because of straight propagation wave. For millimeterwave, the dielectric ceramics with high quality factor (Q$.$f), low dielectric constant($\varepsilon$), and nearly zero temperature coefficient of resonant frequency ($\tau$) are needed. No microwave dielectric ceramics with these three properties exist except Ba(Mg$\_$1/3/Ta/sub1/3/)O$_3$ (BMT), which has a little high s: In this paper, alumina (Al$_2$O$_3$) and fosterite (Mg$_2$SiO$_4$), candidates for millimeter-wave applications, were studied with an objective to get high q$.$f and nearly zero $\tau$$\_$f/ For alumina ceramics, q$.$f more than 680,000 GHz was obtained but it was difficult to obtain nearly zero Qf. On the other hand, for forsterite ceramics, q$.$f was achieved from 10,000 GHz of commercial for sterite to 240,000 GHz of highly purified MgO and SiO$_2$ raw materials, and $\tau$$\_$f/ was reduced a few by adding TiO$_2$ with high positive $\tau$$\_$f/.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.356-360
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• 2017

We investigated the phase evolution, microstructure, and microwave dielectric properties of Na- and Zr-doped $Ba(Mg_{0.5}W_{0.5})O_3$ [i.e., ($Ba_{1-2x}Na_{2x})(Mg_{0.5-x}Zr_xW_{0.5})O_3$] ceramics. $BaWO_4$ as a secondary phase was observed in all compositions, and it increased as the dopant concentration increased. All specimens revealed a dense microstructure. For the composition of x=0.01, polyhedral grains were observed. As the dopant concentration increased, the densification and the grain growth were promoted by a liquid phase. The quality factor($Q{\times}f_0$) decreased remarkably, whereas the dielectric constant (${\varepsilon}_r$) tended to decrease as the dopant concentration increased. The dielectric constant, quality factor, and temperature coefficient of the resonant frequency of the composition of x=0.01 sintered at $1,700^{\circ}C$ for 1 h were 18.6, 216,275 GHz, and $-22.0ppm/^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.57-61
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• 2005

The microwave dielectric properties of 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics with H$_3$BO$_3$-SnO were investigated to improve the sintering condition for the LTCC. According to the X-ray diffraction patterns, 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics with H$_3$BO$_3$-SnO had the columbite structure of TiTe$_3$O$_{8}$ phase and the ilmenite structure of MgTiO$_3$ phase and there were no second phase. Increasing the addition of H$_3$BO$_3$-SnO, the density and dielectric constant of the 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics were increased but the quality factor was decreased. The temperature coefficient of resonant frequency was shifted to the negative(-) direction with addition of H$_3$BO$_3$-SnO.EX>-SnO.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.364-367
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• 2018

The phase evolution, microstructure, and microwave dielectric properties of Sr-substituted $Ba(Mg_{0.5}W_{0.5})O_3$ ceramics, i.e., $(Ba_{1-x}Sr_x)(Mg_{0.5}W_{0.5})O_3$ ($0{\leq}x{\leq}0.30$), sintered at $1700^{\circ}C$ for 1 h were investigated. All compositions showed a 1 : 1 ordered perovskite structure. In all the compositions, $BaWO_4$ was detected as the secondary phase. With increasing x in ($Ba_{1-x}Sr_x$) $(Mg_{0.5}W_{0.5})O_3$, the lattice parameter increased linearly, indicating that a substitutional solid solution occurred. All compositions exhibited a dense microstructure. The value of ${\varepsilon}_r$ increased slightly with increasing x. The value of $Q{\times}f_0$ increased with the increase in x up to x = 0.10 and reached a saturated value of about 100,000 GHz. The composition for x = 0.20, i.e., $(Ba_{0.80}Sr_{0.20})(Mg_{0.5}W_{0.5})O_3$, sintered at $1700^{\circ}C$ for 1 h exhibited superior microwave dielectric properties of ${\varepsilon}_r=19.6$, $Q{\times}f_0=99,358GHz$, and ${\tau}_f=0.0ppm/^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.246-250
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• 1995

Microwave properties of $CaTiO_{3}$, MgO and CaO added $MgTiO_{3}$ ceramics are investigated. In the composition of $(Mg_{0.915}Ca_{0.085})TiO_3$, dielectric constant($varepsilon _T$) was 22, Qxf value was 50000, and temperature coefficient of resonant frequency($gamma_T$) approached to near zero $ppm/^{\circ}C$.$MgTiO_{3}$ ceramics with 0.1 mol of MgO showed the highest Qxf calue of 131000, dielectric constant of 17, and r, of -$50ppm/^{\circ}C$. Dielectric constant of 8 mol% CaO added to $MgTiO_{3}$-MgO was 20. Qxf valus was 52000, and sf was zero $ppm/^{\circ}C$. $MgTiO_{3}$-Mg0-Ca0 system showed higher Qxf value than ($Mg_{1-x}, Ca_x$) Ti03 system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.7
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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.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.995-1004
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• 1994

Phase relation and microwave dielectric properties of the system BaO.(Nd1-xSmx)2O3.TiO2 (n=4, 5) were studied. With n=5 (1 : 1 : 5), Ba2Ti9O20 and TiO2 formed in case of X$\leq$0.7, and Ba2Ti9O20 and Sm2Ti2O7 formed at X=1.0 as the second phases dispersed in fine-grained orthorhombic matrix phase. With n=4 (1 : 1 : 4). on the contrary, only fine grains of an ortho-rhombic phase were observed irrespective of Nd/Sm ratio. The compositions of these two stable orthorombic phases having distinct lattic constants even with the same Nd/Sm ratio were estimated as 4BaO.5(Nd1-xSmx)2O3.18TiO2 and BaO.(Nd1-xSmx)2O3.4TiO2 with n=5 and n=4 in the system BaO.(Nd1-xSmx)2O3.TiO2, respectively. Consequently the composition BaO.(Nd1-xSmx)2O3.5TiO2 lies in the compatible triangle of 4BaO.5(Nd1-xSmx)2O3.18TiO2 and the second phases mentioned above. The microwave dielectric properties (~4 GHz) of BaO.(Nd1-xSmx)2O3.5TiO2 can be controlled effectively by adjusting Sm content : with increasing X from 0 to 0.7, both dielectric constant and the temperature coefficient of resonant frequency decreased monotonically from 82 to 65 and from 91 (ppm/$^{\circ}C$) to -19(ppm/$^{\circ}C$), respectively, while unloaded Q(Qo) remained constant at about 2,600.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.8
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• pp.1068-1074
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• 1995

Effect of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ addition on the phase changes and microwave dielectric properties of BaTi $O_{3}$-3Ti $O_{2}$ ceramics were investigated. Addition of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ to BaTi $O_{3}$-3Ti $O_{2}$ resulted in the formation of Ba $Ti_{4}$$O_{9}$, $Ba_{2}$ $Ti_{9}$ $O_{20}$, Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_{3}$, and Ti $O_{2}$ phases. Ba $Ti_{4}$$O_{9}$ phase was gradually transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$. This was identified by XRD and microstructure. As the Ba $Ti_{4}$$O_{9}$ phase transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$ phase, the dielectric constant increased to 37.5. Q*f$_{o}$ value was 40000 at x=0.04, and the temperature coefficient of resonant frequency was +10ppm/.deg. C.C.. C.C.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.635-638
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• 2004

페로브스카이트 구조를 가지는 $CaZrO_3$ 유전체 세라믹스에 $CaTiO_3$를 부피 비율로 첨가하여 첨가량 변동에 따른 마이크로파 유전 특성을 조사하였다. 또한 저온 동시소성 기능성 LTCC 기판용 유전체 소재로서 활용하기 위하여 저융점의 borosilicate계 유리 프리트를 첨가하여 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스의 저온 소결 거동과 마이크로파 유전 특성을 평가하였다. 알칼리가 첨가된 저융점의 borosilicate계 유리 프리트를 $10\sim30$ wt% 범위로 첨가함으로서 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스의 소결온도를 $1450^{\circ}C$에서 $900^{\circ}C$이하로 낮출 수 있었으며, 유리 프리트의 첨가량으로 공진 주파수 온도계수 특성을 조절할 수 있었다. 유리 프리트의 첨가량이 15 wt% 첨가시 $875^{\circ}C$에서 충분한 소결이 이루어졌으며, 이 경우 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스는 유전율(k) 23, 품질계수(Qxf) 2500, 공진 주파수 온도계수 ($\tau_{cf}$) -3 ppm/$^{\circ}C$의 매우 양호한 마이크로파 유전 특성을 나타내었다. 유리 프리트의 첨가에 의하여 소결 과정에서 주상인 $CaZrO_3$가 $CaZr_4O_9$ 상으로의 변화가 뚜렷이 나타났는데, 이러한 상전이 현상과 함께 미세구조의 변화에 대해서도 고찰하였다.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.346-349
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• 2003

Microwave dielectric characteristics and physical properties of the new Zr$_{1-x}$ (Bn$_{1}$3/Nb$_{2/3}$)xTi $O_4$ (0.2$\leq$x$\geq$ 1.0) system have been investigated as a function of the amount of Bn$_{1}$3/Nb$_{2/3}$ $O_2$substitution. With increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ content (x), two phase regions were observed: $\alpha$-Pb $O_2$ solid solution (x<0.4), mixture of the rutile type Zn$_{1}$3/Nb$_{2/3}$Ti $O_4$ and the $\alpha$-Pb $O_2$ solid solution (x$\geq$0.4). In the$\alpha$-Pb $O_2$solid solution region below x<0.4, the Q.f$_{0}$ value sharply increased and the Temperature Coefficient of the Resonant Frequency(TCF) decreased with increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ contents while dielectric constant (K) showed nearly same value. In the mixture region above x$\geq$4, the dielectric constant and TCF increased with increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ content. Zr$_{1-x}$ (Zn$_{1}$3/Nb$_{2/3}$)xTi $O_4$ materials have excellent microwave dielectric properties with K=44.0, Q.f$_{0}$ : 41000 GHz and TCF =-3.0 ppm/$^{\circ}C$ at x=0.35.=0.35. x=0.35.=0.35.