• 한국전기전자재료학회논문지
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• 제24권11호
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• pp.855-858
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• 2011

In this paper, in order to suppress unwanted current paths originating from adjacent cells in a passive crossbar array based on resistive random access memory (RRAM) without extrinsic switching devices, 1-diode type RRAM which consists of a 0.2% chromium-doped strontium titanate (Cr-$SrTiO_3$) film deposited on a silicon substrate, was proposed for high packing density, and intrinsic rectifying characteristics from the current versus voltage characteristics were successfully demonstrated.

• Transactions on Electrical and Electronic Materials
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• 제4권2호
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• pp.24-28
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• 2003

(Ba,Sr,Ca)TiO$_3$ powders, prepared by the sol-gel method, were mixed with organic binder and the BSCT thick films were fabricated by the screen printing techniques on alumina substrates. All the BSCT thick films, sintered at 1420$^{\circ}C$, showed the typical XRD patterns of a perovskite polycrystalline structure. The average grain sizes decreased with increasing amounts of ZrO$_2$, and the BSCT(40/40/20) thick films doped with 2wt% MnO$_2$ showed a value of 8$\mu\textrm{m}$. The thickness of thick films by four-cycle on printing/drying was approximately 951$\mu\textrm{m}$. The relative dielectric constant decreased with increasing Ca content and MnO$_2$ doping amount. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) thick films doped with 2.0wt% ZrO$_2$ were 772, 0.184％ and 15.62%, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.616-619
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• 2003

This work presents the design, fabrication and microwave performance of distributed analog phase shifter (DAPS) fabricated on $(Ba,\;Sr)TiO_3$ (BST) thin films for X-band applications. Ferroelectric BST thin films were deposited on MgO substrates by pulsed laser deposition. The DAPS consists of high impedance coplanar waveguide (CPW) and periodically loaded tunable BST interdigitated capacitors (IDC). In order to reduce the insertion loss of DAPS and to remove the alteration of unloaded CPW properties according to an applied dc bias voltage, BST layer under transmission lines were removed by photolithography and RF-ion milling. The measured results are in good agreement with the simulated results at the frequencies of interest. The measured differential phase shift based on BST thin films was $24^{\circ}$ and the insertion loss decreased from 1.1 dB to 0.7 dB with increasing the bias voltage from 0 to 40V at 10 GHz.

• 한국결정성장학회지
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• 제20권1호
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• pp.21-24
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• 2010

고주파 유전체 세라믹 $(Ca_{0.7}Sr_{0.3})_m(Ti_yZr_{1-y})O_3$ 의 미세구조 및 전기적 특성에 대한 Ti 이온 및 몰비의 영향을 조사하였다. $CaZrO_3$의 Zr 위치에 Ti 이온의 치환은 세라믹 소체의 소결밀도 및 미세구조에 큰 영향을 미친다. Zr 위치에 Ti 이온의 치환량 증가에 따라, 소결밀도는 급격히 증가하고, 몰비 m=1.01에서 치밀한 미세조직이 얻어졌다. 한편, 몰비 m=0.99 조성에 대해서는 Ti 치환량이 증가하여도 소결밀도 및 미세구조는 거의 변화가 없이 일정하였다. Ti 치환량 증가에 따라 TCC (temperature coeITicient of capacitance) 곡선은 시계방향으로 회전하여 몰비 m=0.99, 1.01 조성에 대해 COG 특성을 만족하였다. $CaZrO_3$의 TCC 및 소결특성 제어를 위해서는 Ti 치환량이 몰비보다는 효과적임을 보여준다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.344-345
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• 2006

In this study, in order to develop low temperature sintering piezoelectric transformer, $(Pb_{0.99-x}Ca_xSr_{0.01})Ti_{0.96}(Mn_{1/3}Sb_{2/3})_{0.04}O_3$ ceramic systems were fabricated using $Na_2CO_3-Li_2CO_3$ as sintering aids and investigated with the amount of Ca substitution. The piezoelectric transformer requires high electromechanical coupling factor $k_t$ and high mechanical quality factor $Q_{mt}$ for generating high output power At the ($PbCaSr)Ti(MnSb)O_3$ ceramics with 24mol% Ca substitution sintered at $900^{\circ}C$, electromechanical coupling factor $k_t$ and mechanical quality factor $Q_{mt}$ showed the optimal values of 0.504 and 1655 respectively, for thickness vibration mode multilayer piezoelectric transformer application.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.1-7
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• 2021

This study investigated the structural, dielectric, ferroelectric, and strain properties of (0.98-x)Bi1/2Na1/2TiO3-0.02BiFeO3-xSrTiO3 (BNT-BF-100xST, x＝0.20, 0.22, 0.24, 0.26, and 0.28). All samples were successfully synthesized using the conventional solid-state reaction method and sintered at 1,175℃ for 2 h. The average grain size of the BNT-BF-100x ceramics decreased with increasing ST content. Furthermore, we observed that the ferroelectric- relaxor transition temperature (TF-R) decreased with increasing ST content, which eventually vanished in the BNT-BF-24ST ceramics. The results indicated that a ferroelectric to relaxor phase transition could be induced by ST modification. Consequently, a large electromechanical strain of 633 pm/V at 4 kV/mm was observed for the BNT-BF-26ST ceramics. These results imply that our materials have the competitive advantage of larger strain under lower operating field conditions compared with other BNT-based lead-free piezoelectric ceramics. We expect that BNT-BF-ST lead-free piezoelectric ceramics are promising candidates as a novel ternary BNT-based system and can find potential applications in actuators.

• 한국세라믹학회지
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• 제35권7호
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• pp.679-684
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• 1998

Dielectricand pyroelectric properties of {{{{ { { {Ba }_{0.67 }Sr }_{0.33 } }`TiO_{3 } ^{ } }} (BST) thin plates and films were investigated. For BST thin plates maximum dielectric constant and pyrolelectric coefficient were observed at around 24$^{\circ}C$ and pyroelectric characteristics were improved as applied bias field was increased. When the electric field of 4kV/cm was applied to the thin plates sintered at 140$0^{\circ}C$ the pyroelectric coefficients over 4$\times$10-7C/{{{{ { cm}^{2 }K }} were obtained in the range of 0-4$0^{\circ}C$ BST thin films deposited using rf magnetron sputtering showed [001] preferred orientation at substrate temperatures above 50$0^{\circ}C$ On the contrary to the thin plates the dielectric constants of the thin films gradually increased above 15$^{\circ}C$ and decreased as applied bias field in-creased. The pyroelectric coefficients of thin films were lower than 1/10 those of thin plates.

• 센서학회지
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• 제3권3호
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• pp.3-8
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• 1994

정온발열 특성을 갖는 PTC 써어미스터를 사용하여 유속센서를 제조하였다. $(Ba_{0.7}Sr_{0.3})TiO_{3}$ 분말을 사용하여 PTC 써어미스터를 제조한 후, 유속에 따른 저항률의 변화를 조사하였다. 유속이 0 cm/s에서 5 cm/s로 변할 경우 저항률은 4.45 $k{\Omega}{\cdot}cm$에서 3.95 $k{\Omega}{\cdot}cm$로 변하였다. 유속이 1 cm/s와 5 cm/s일 경우 PTC 써어미스터의 감도는 -204 (${\Omega}{\cdot}cm$)/(cm/s)와 -24 (${\Omega}{\cdot}cm$)/(cm/s)로 나타났다.

• 암석학회지
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• 제12권3호
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• pp.119-134
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• 2003

육십령 복운모화강암은 광물학$.$지화학적으로 과알루미나 성질을 특징적으로 나타낸다. 육십령 화강암체는 1.15∼l.20 범위의 높은 알루미나 포화 지수와 2.20∼2.98wt% 범위의 높은 CIPW norm 강옥 함량을 나타낸다. 색지수는 <16%이고, FeO$^{T}$ +MgO+TiO$_2$,는 평균 1.9 wt%로서 우백질화강암에 해당한다. 육십령 복운모 우백질화강암은 SiO$_2$성분이 증가함에 따라, TiO$_2$, $Al_2$O$_3$, FeO, Fe$_2$O$_3$, MgO, CaO, $K_2$O, P$_2$O$_{5}$ , Rb, Ba, Sr 은 감소하는 경향을 나타내는 반면, Zr과 Th는 증가하는 경향을 나타내는데, 이는 장석, 흑운모, 인회석 저어콘의 분별경정작용에 기인한 것으로 해석된다. 거정질 암맥에는 SiO$_2$and P$_2$O$_{5}$ 는 높게, 그 외의 주원소는 결핍되어 나타난다. Manaslu, Hercynian 복운모 우백질화강암, Lachlan습곡대의 S-형 화강암과 비교해 보면, 육십령 복운모 우백질화강암은 낮은 Rb, 높은 Ba, Sr을 나타낸다. 거정질 암맥의 지화학적 특징은 육십령 복운모화강암을 형성했던 멜트로부터 일부 원소들의 제거 혹은 유동성에 의해 높은 Rb, Nb와, 낮은 Ba, Sr, Zr, Th, Pb 함유를 나타낸다. 육십령 복운모 우백질화강암은 총 휘토류 함량이 95.7∼123.3ppm 범위를 나타내며, 운석에 대해 표준해보면, 저 내지 중정도의 Eu 이상(Eu/Eu＊= 0.7∼0.9)을 가지면서 경희토류원소가 풍부하고 중희토류원소가 결핍된 매우 경사가 져 있는((La/Yb)$_{N}$ = 6.9∼24.8) 변화를 보여준다. 반면에 페그마틱 암맥은 총 휘토류원소의 함량이 7.0ppm으로 운석에 대해 표준화하면, 강한 부의 Eu 이상(Eu/Eu＊= 0.2)을 가진 편평한 양상을 나타낸다. 복운모 우백질화강암을 형성했던 멜트의 성분은 기원암 뿐만 아니라 기원암이 녹은 후의 잔류물질의 양에도 의존한다. 특히 CaO/$Na_2$O의 비와 Rb/Sr-Rb/Ba의 비들은 강한 과알루미나질 화강암에서는 기원암의 성분에, 즉, 기원암의 사장석과 점토 함량 비에 주로 의존한다. 육십령 복운모 우백질화강암은 사장석 성분보다 점토 성분이 풍부한 암석에서 기원한 Manaslu와 Hercynian 복운모 우백질화강암들(예를 들면 Millevaches와 Gueret)보다는 더 높은 CaO/$Na_2$O의 비와 더 낮은 Rb/Sr-Rb/Ba 비를 나타내고 있는데, 이러한 지화학적 특징은 점토 성분보다는 사장석이 풍부한 석영장석질 암석으로부터 기원했던 것으로 사료된다.

• 한국전기전자재료학회논문지
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• 제13권2호
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• pp.143-150
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• 2000

Ferroelectric SrxBi2+yTa2O9+$\alpha$ thin films with various compositions(x=0.7, 0.8, 1, y=0.3, 0.4) were prepared by sol-gel method. The film with moled ratio of 0.8:2.3:2.0 in Sr/Bi/Ta, which was deposited on Pt/SiO2/Si (100), showed better ferroelectric properties than other films. To investigate substrate effects, the same compositions were spin coated on Pt/Ti/SiO2/Si (100) substrates. At an applied voltage of 5V, the dielectric constant($\varepsilon$r), remanent polarization (2Pr) and coercive field (Ec) of the Sr0.8Bi2.3Ta2O9+$\alpha$ thin film prepared on Pt/Ti/SiO2/Si (100) were about 296, 24$\mu$C/$\textrm{cm}^2$ and Ec of 49kV/cm respectively. Both SBT films firred at 80$0^{\circ}C$ revealed no fatigue up to 1010 cycles. Retention characteristics of these capacitors showed no degradation up to 104 sec.