• 한국전기전자재료학회논문지
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• 제28권4호
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• pp.229-233
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• 2015

In this paper, in order to develop outstanding Pb-free piezoelectric composition ceramics, the $(Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3+0.3wt%Bi_2O_3+0.4wt%Fe_2O_3+xwt%CuO$ (x= 0~0.8 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effects of CuO-doping on the structure and electrical properties of the NKL-NST ceramics were systematically studied. The results show that the ceramics exhibit a pure perovskite structure with orthorhombic phase at room temperature, and secondary phase was found in the ceramics. The 0.4 wt%CuO added ceramics sintered at $950^{\circ}C$ showed the optimum properties of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : $d_{33}=213$[pC/N], kp= 0.43, Qm= 423,respectively.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권12호
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• pp.553-558
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• 2003

The A S $r_{0.7}$B $i_{2.6}$T $a_2$ $O_{9}$ (SBT)thin films are deposited on Pt-coated electrode(Pt/$TiO_2$/$SiO_2$/Si) using a RF magnetron sputtering method. The electrical properties of SBT capacitors with top electrodes were studied. In the XRD pattern, the SBT thin films in all annealing temperatures had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized at 75$0^{\circ}C$ and grains largely grew in oxygen annealing atmosphere. The electrical properties of SBT capacitor with top electrodes represent a favorable properties in Pt electrode. The maximum remanent polarization and the coercive electric field with Pt electrode are 12.40C/$\textrm{cm}^2$ and 30kV/cm, respectively. The dielectric constant and leakage current density with Pt electrode is 340 and 6.8110$^{-10}$ A/$\textrm{cm}^2$, respectively.y.y.

• 한국전기전자재료학회논문지
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• 제28권10호
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• pp.615-619
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• 2015

In this study, in order to develop the composition ceramics with the excellent electrocaloric properties, 8/65/35 PLZT ceramics were fabricated by the conventional solid-state method with the addition of $Bi_2O_3$, CuO, $Li_2CO_3$ and the variation of sintering temperature from $930^{\circ}C$ to $990^{\circ}C$. The XRD pattern of all specimens indicated general perovskite structure and the rhombohedral phase were observed. Curie temperature ($T_c$) of all specimens was observed in the vicinity of about $190^{\circ}C$. Density, coercive field and remnant polarization of the specimen sintered at $950^{\circ}C$ was $7.55g/cm^3$, 8.895 kV/cm, $11.22{\mu}C/cm^2$, respectively. EC effect of PLZT ceramics was measured by indirect method and the temperature change ${\Delta}T$ due to the electrocaloric effect was calculated by Maxwell's relations. ${\Delta}T$ of ceramic sintered at $950^{\circ}C$ was $0.21^{\circ}C$ under application of 40 kV/cm at $190^{\circ}C$.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.270-273
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• 2012

x mol% (x = 0 ~ 20) Na2CO3 excess Bi2.5Na3.5Nb5O18 (BNN) particles were synthesized using molten salt as a flux. The secondary phases were observed at stoichiometric ratio of BNN precursors and their intensity decreased with increasing Na contents. The results of SEM images showed that all particles existed in a platelet shape and the particle increased in size with higher increasing Na contents. Plate-like NaNbO3 particles were developed using BNN precursor obtained by a topochemical microcrystal conversion. XRD analysis of NaNbO3 particles showed that a single perovskite phase and the intensity of (h00) peaks increased with increasing Na contents in BNN precursor. SEM images showed that the size of plate-like NaNbO3 was significantly changed by controlling Na contents in BNN precursors.

• 마이크로전자및패키징학회지
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• 제10권2호
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• pp.49-54
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• 2003

본 연구에서는 Pt/SrBi$_2$Ta$_2$O$_{9}$(SBT)/Si (MFS)와 Pt/SBT/Pt (MFM) 각각의 구조에서 수소 열처리에 의한 SBT박막의 물리, 전기적 영향에 대해 연구하였다. SBT 박막의 미세구조 및 전기적 특성은 수소 열처리 후에 SBT 박막의 손상으로 열화된다. 특히, Pt 전극에 의한 SBT 박막의 열화 현상을 연구하기 위해 각각 Si 와 Pt 위에 SBT 를 증착하여 같은 조건으로 열처리를 하였다. XRD, XPS, P-V, C-V 측정을 통해 Pt 전극 없이 SBT자체로도 수소 열처리 후에 열화 됨을 확인 할 수 있었다. 또한, 수소 열화현상이라고 하는 촉매 반응으로 SBT 열화 현상이 Pt로 가속화되었다. 이러한 현상을 방지하기 위해서 새로운 Ir 전극을 제안하여 $Ir/IrO_2/SBT/IrO_2$ 구조에서의 수소 열처리 전후 및 회복 열처리를 통해 SBT 박막의 전기적 특성을 연구하였다. P-V측정을 통해 SBT박막을 이용한 MFM구조에서 Ir이 열화 방지용 전극 물질로의 활용 가능성을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.235-235
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• 2003

The development of a buffer layer is an important issue for the second -generation wire, YBCO coated metal wire. The buffer layer demands not only on the prohibition of the reaction between YBCO and metal substrate, but also the proper lattice match and conductivity for high critical current density (Jc) of YBCO superconductor, In order to satisfy these demands, we suggested CaRuO3 as a useful candidate having that the lattice mismatches with Ni (200) and with YBCO are 8.2% and 8.0%, respectively. The CaRuO3 thin films were deposited on Ni substrates using various methods, such as e-beam evaporation and DC and RF magnetron sputtering. These films were investigated using SEM, XRD, pole-figure and AES. In e-beam evaporation, the deposition temperature of CaRuO3 was the most important since both hi-axial texturing and NiO formation between Ni and CaRuO3 depended on it. Also, the oxygen flow rate had i[n effect on the growth of CaRuO3 on Ni substrates. The optimal conditions of crystal growth and film uniformity were 400$^{\circ}C$, 50 ㎃ and 7 ㎸ when oxygen flow rate was 70∼100sccm In RF magnetron sputtering, CaRuO3 was deposited on Ni substrates with various conditions and annealing temperatures. As a result, the conductivity of CaRuO3 thin films was dependent on CaRuO3 layer thickness and fabrication temperature. We suggested the multi-step deposition, such as two-step deposition with different temperature, to prohibit the NiO formation and to control the hi-axial texture.