복합 페로브스카이트 (1-x)(Li1/2Sm1/2)TiO3-x(Na1/2Sm1/2)TiO3(LNST) system의 유전특성 및 미세구조 관찰 [1]
Dielectric Properties and Microstructure Observation of Complex Perovskite (1-x)(Li1/2Sm1/2)TiO3-x(Na1/2Sm1/2)TiO3(LNST) system [1]
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복합 페로브스카이트 (1-x)(Li1/2Sm1/2)TiO3 - x(Na1/2Sm1/2)TiO3 (LNST) system의 마이크로파 유전특성과 미세구조를 XRD와 SEM을 이용하여 연구하였다. 이 LNST는 산소팔면체의 antiphase tilting 뿐만아니라, inphase tilting과 양이온의 antiparallel shift를 가지는 구조변화는 보인다. 또한 LNST계는 0.0≤x≤0.4에서 양이온(Li+1)의 휘발이 일어나서 A-site vacancy ordering에 의해 c축으로 cell doubling이 일어난다. 미세구조의 관찰을 통해 전 범위의 조성에서 비정상 입성장 현상을 관찰하였다. LNST 계에서 A-site에 Li+1을 치환한 LST의 공진주파수 온도계수는 큰 음의 값(-220 ppm/℃)을 가지나, Na+1을 치환한 NST는 큰 양의 값(+173 ppm/℃)을 가진다. x=0.4일때 4 ㎓에서 εr=103, Q＊f0=3,700 ㎓ 그리고 Tcf=+50 ppm/℃의 좋은 유전특성을 얻었다.
Abstract
The microwave dielectric properties and microstructures of the Complex Perovskite (1-x)(Li1/2Sm1/2)TiO3 - x(Na1/2Sm1/2)TiO3 (LNST) system were investigated using the X-ray diffraction(XRD) and scanning electron microscopy(SEM). LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations. Also, when 0.0≤x≤0.4, LNST had the vacancy ordering of A-sites because of the evaporation of Li ions. From the observation of the microstructure, abnormal grain growth phenomena were observed over the whole range of x. The temperature coefficient of resonant frequency(Tcf) of the (Li1/2+1Sm1/2+3)TiO3 (LST) system has a large negative value(-220 ppm/℃) but the (Na1/2+1Sm1/2+3)TiO3 (NST) system which substituted Na+1 has a large positive value(+173 ppm/℃). The dielectric properties of εr=103, Q＊f0=3,700 ㎓ and Tcf=+50 ppm/℃ at 4 ㎓ were obtained when x=0.4.
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