초록

유전율이 높고 온도안정성이우수하다고 알려져 있는 Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 계 세라믹스를 산화물혼합법 및 precursor방법으로 제조함에 있어 과잉 MgO의 첨가에 따른 미세구조와 유전특성의 변화에 대하여 조사하였다. MgO를 5mol%이상 과잉첨가하여 100$0^{\circ}C$에 소결한 시편의 유전율은 5000이상이고, -55$^{\circ}C$에서 1$25^{\circ}C$범위에서 변화율은 +25%에서 -5$0^{\circ}C$ 정도를 나타냈다. XRD 분석결과 perovskite상과 Pb2WO5 결정이 주된상이었으며, 소결온도 및 MgO 첨가량이 증가함에 따라 cubic pyrochlore상인 Pb3Nb4O13와 PbWO4는 감소하였다. SEM에 의한 미세구조의 관찰에서 MgO첨가량이 증가함에 따라 결정성장이 촉진되는 것을 알 수 있었으며 이것이 소결온도 증가에 따른 pyrochlore상의 감소와 함께 유전율을 증가시키는 원인이었다. BSE관찰에서 화학성분 분포의 불균일성이 나타났으며, 각각의 소결온도에서 생성되는 결정상과 함께 유전율의 온도의존성을 완만하게 만드는 원인임을 알 수 있었다.

Abstract

The effects of 0 to 10mol% excess MgO addition on the microstructure and dielectric properties in 30Pb(Mg1/3Nb2/3)O3-20PbTiO3-50Pb(Mg1/2W1/2)O3 ternary system were investigated. Samples were prepared by mixed oxide and precursor methods to compare the role of excess MgO. Excess MgO enhanced grain growth and increased dielectric constant. The dielectric constant and tesmperature dependence of dielectric constant of the sample sintered at 100$0^{\circ}C$ with 5mol% MgO were above 5,000 and +25% to -50% from - 55$^{\circ}C$ to 1$25^{\circ}C$, respectively. For these specimens the phases percent were mainly perovskite and Pb2WO5, which was confirmed by XRD analysis. Also the amount of cubic pyrochlore Pb3Nb4O13 and PbWO4 were de-creased with sintering temperature and MgO addition. BSE image showed the chemical inhomogeneous dis-tribution. Crystal phase formed at each sintering temperature and the chemical inhomogeneous distribution caused the decrease of the temperature dependence of dielectric constant.

주제어

#Dielectric properties   #Microstructure   #Temperature dependence of dielectric constant   #Excess MgO ad-dition  

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