• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.71-72
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• 1988

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.221-224
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• 2000

The microwave dielectric properties of Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BMT-BCN] ceramics were investigated. The specimens were prepared by the conventional mixed oxide method. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$ and Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$ formed a solid solution with complex perovskite structure. Increasing the BCN content, dielectric constant was increased, but temperature coefficient of resonant frequency was decreased. In the range of x$\geq$0.4, dielectric constant was about 30. 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Q$\times$f$_{0}$=75,325[GHz] and $\tau$$_{f}$=-2.9015[ppm/$^{\circ}C$].X>].

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.325-331
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• 1999

SrWO4가 첨가된 (Sr1-xBax)(Mg1/3Nb2/3)O3의 마이크로파 유전특성에 관하여 조사하였다. 관찰된 조성영역에서 Sr(Mg1/3Nb2/3)O3과 Ba(Mg1/3Nb2/3)O3은 (Sr1-xBax)(Mg1/3Nb2/3)O3고용체를 형성하고 SrWO4의 첨가는 고용체의 소결성을 향상시켜 소결온도 155$0^{\circ}C$에서 상대밀도 97% 이상을 얻었다. 소결한 시편의 EDS분석결과, SrWO4의 첨가량이 많은 시편에서 2차상이 존재하는 것을 알수 있었다. 순수한 Sr(Mg1/3Nb2/3)O3에 SrWO4를 0.01 mole첨가하여 1550~1$600^{\circ}C$에서 소결한 시편의 유전특성은 $\varepsilon$r 30, Q$\times$fo$\geq$55000,$ au$f -23 ppm/$^{\circ}C$이었다. 0.01 mole SrWO4가 첨가된 (Sr1-xBax)(Mg1/3Nb2/3)O3 고용체의 유전율과 온도계숙가 x에 따라 점차적으로 계속 증가하였고 Q$\times$fo는 x$\leq$0.25에서 x에 따라 감소하고 x$\geq$0.3에서 다시 증가하였다. (Sr0.65Ba0.35)(Mg1/3Nb2/3)O3+0.01SrWO4의 조성을 갖는 시편에서 $\varepsilon$r 34.4, Q$\times$fo$\geq$55000,$\tau$f 0 ppm/$^{\circ}C$이었다.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1664-1666
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• 2000

The structural and microwave properties of Ba($Mg_{1/3}Ta_{2/3})O_3$-Ba($Co_{1/3}Nb_{2/3})O_3$ ceramics were investigated with composition ratio. The specimens were sintered at 1525$^{\circ}C$ for 5 hours in air. All specimens exhibited superlattice reflection planes of (100), (111), (200), (201), and (112). Increasing mole ratio of BCN ceramics, the peak intensity of superstructure reflection plane were decreased, while dielectric constant was slightly increased. The dielectric constant and quality factor of the 0.8BMT-0.2BCN ceramics were 27.51, 103,681 [at 1GHz], respectively.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1443-1448
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• 1994

Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 solid solution was formed by mixed-oxide method. The phase during formation was analysed by XRD and formation mechanism was investigated. While heat-treating Pb(Mg1/3Nb2/3)O3 composition, the first, Pb2Nb2O7 and Pb3Nb2O8 pyrochlore phases are formed, and finally Pb(Mg1/3Nb2/3)O3 perovskite phase with containing Pb3Nb4O13 pyrochlore phase is obtained at 80$0^{\circ}C$. When Pb(Mg1/3Nb2/3)O3 composition is modified with PbTiO3 which have strong ionic bonding and high tolerance factor, the amount of pyrochlore phase is decreased by increasing of stability in perovskite structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.38-42
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• 2005

B$_2$O$_3$ added Ba(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ (BBMN) ceramics were not sintered below 900 $^{\circ}C$. However, when CuO was added to the BBMN ceramic, it was sintered even at 850 $^{\circ}C$. The amount of the $Ba_2$B$_2$O$_{5}$ second phase decreased with the addition of CuO. Therefore, the CuO additive is considered to react with the B$_2$O$_3$ inhibiting the reaction between B$_2$O$_3$ and BaO. Moreover, it is suggested that the solid solution of CuO and B$_2$O$_3$ might be responsible for the decrease of the sintering temperature of the specimens. A dense microstructure without pores was developed with the addition of a small amount of CuO. However, a porous microstructure with large pores was formed when a large amount of CuO was added. The bulk density, the dielectric constant ($\varepsilon$$_{r}$) and the Q-value increased with the addition of CuO but they decreased when a large amount of CuO was added. The variations of those properties are closely related to the variation of the microstructure. The excellent microwave dielectric properties of Qxf = 21500 GHz, $\varepsilon$$_{r}$ = 31 and temperature coefficient of resonance frequency($\tau$$_{f}$) = 21.3 ppm/$^{\circ}C$ were obtained for the Ba(Mg$_{1}$3/Nb$_{2}$3/)O$_3$+2.0 mol%B$_2$O$_3$+10.0 mol%CuO ceramic sintered at 875 $^{\circ}C$ for 2 h.h.2 h.h.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.838-841
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• 2004

[ $B_2O_3$ ] added $Ba(Mg_{1/3}Nb_{2/3})O_3$ (BBMN) ceramics were not sintered below $900^{\circ}C$. However, when CuO was added to the BBMN ceramic, it was sintered even at $850^{\circ}C$. The amount of the $Ba_2B_2O_5$ second phase decreased with the addition of CuO. Therefore, the CuO additive is considered to react with the $B_2O_3$ inhibiting the reaction between $B_2O_3$ and BaO. Moreover, it is suggested that the solid solution of CuO and $B_2O_3$ might be responsible for the decrease of the sintering temperature of the specimens. A dense microstructure without pores was developed with the addition of a small amount of CuO. However, a porous microstructure with large pores was formed when a large amount of CuO was added. The bulk density the dielectric constant $({\varepsilon}_r)$ and the Q-value increased with the addition of CuO but they decreased when a large amount of CuO was added. The variations of those properties are closely related to the variation of the microstructure. The excellent microwave dielectric properties of Qxf=21500 GHz, ${\varepsilon}_r=31$ and temperature coefficient of resonance frequency$({\tau}_f)=21.3\;ppm/^{\circ}C$ were obtained for the $Ba(Mg_{1/3}Nb_{2/3})O_3+2.0\;mol%B_2O_3+10.0$ mol%CuO ceramic sintered at $875^{\circ}C$ for 2h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.30-37
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• 2005

The microwave dielectric properties and their related structural characteristics in solid solutions of (1-$\chi$) Ba($Mg_{1/3}$Nb$_{2/3}$) $O_3$-$\chi$La(Mg$_{2/3}$Nb$_{1}$3) $O_3$(BLMN) have been investigated by measuring the dielectric constant($\varepsilon$r), Q value and temperature coefficient of resonant frequency($\tau$f) and by observing the crystal structure using high resolution transmission electron microscopy (HRTEM). Microwave dielectric properties showed characteristic features for specific composition. Dielectric constant($\varepsilon$$_{r}$) showed maximum value at the composition which corresponds to the phase boundary between 1 : 2 ordered and 1 : 1 ordered structure. The increase in $\varepsilon$$_{r}$ may be caused by the rattling of ions by incorporating smaller ions and the disordered structure. The variation of temperature coefficient of resonant frequency($\tau$$_{f}$) was investigated in terms of oxygen octahedra tilting.dra tilting.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.252-255
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• 1999

The effect of calcination temperature(1st and 2nd calcining at 110$0^{\circ}C$ , 120$0^{\circ}C$ and 130$0^{\circ}C$ respectively) on physical properties of BMNT Ceramics ware investigated. The optimum 1st and 2nd calcination temperature were 120$0^{\circ}C$ , and sintering temperature was 155$0^{\circ}C$. In this condition, the sintering density was 7.53 [g/㎤] and the dielectric constant, Q.f$_{0}$ and $\tau$$_{r}$ were 26, 80, 300[GHz] and +1.5[ppm/$^{\circ}C$] respectively in the microwave range.e.e.