An all-perovskite oxide heterostructure composed of SrSnO3/Nb-doped SrTiO3 was fabricated using the pulsed laser deposition method. In-plane and out-of-plane structural characterization of the fabricated films were analyzed by x-ray diffraction with θ-2θ scans and φ scans. X-ray photoelectron spectroscopy measurement was performed to check the film’s composition. The electrical transport characteristic of the heterostructure was determined by applying a pulsed dc bias across the interface. Unusual transport properties of the interface between the SrSnO3 and Nb-doped SrTiO3 were investigated at temperatures from 100 to 300 K. A diodelike rectifying behavior was observed in the temperature-dependent current-voltage (IV) measurements. The forward current showed the typical IV characteristics of p-n junctions or Schottky diodes, and were perfectly fitted using the thermionic emission model. Two regions with different transport mechanism were detected, and the boundary curve was expressed by ln I = -1.28V - 13. Under reverse bias, however, the temperature- dependent IV curves revealed an unusual increase in the reverse-bias current with decreasing temperature, indicating tunneling effects at the interface. The Poole-Frenkel emission was used to explain this electrical transport mechanism under the reverse voltages.

(Bi1/2Na1/2)TiO3 (BNT)-based ceramics are considered promising candidates for actuator application owing to their excellent electromechanical strain properties However, to obtain large strain properties, there remain several issues such as thermal stability and high operating fields. Therefore, this study investigates a reduction of operating field in (0.98-x)Bi1/2Na1/ 2TiO3-0.02 BiAlO3-xSrTiO3 (BNT-2BA-100xST, x = 0.20, 0.21, 0.22, 0.23, and 0.24) via analyses of the microstructure, crystal structure, dielectric, polarization, ferroelectric and electromechanical strain properties. The average grain size of BNT-2BA- 100xST ceramics decreases with increasing ST content. Results of polarization and electromechanical strain properties indicate that a ferroelectric to relaxor state transition is induced by ST modification. As a consequence, a large electromechanical strain of 592 pm/V is obtained at a relatively low electric field of 4 kV/mm in 22 mol% ST-modified BNT-2BA ceramics. We believe that the materials synthesized in this study are promising candidates for actuator applications.

Orthorhombic DyMnO3 films are fabricated epitaxially on Nb-1.0 wt%-doped SrTiO3 single crystal substrates using pulsed laser deposition technique. The structure of the deposited DyMnO3 films is studied by X-ray diffraction, and the epitaxial relationship between the film and the substrate is determined. The electrical transport properties reveal the diodelike rectifying behaviors in the all-perovskite oxide junctions over a wide temperature range (100 ~ 340 K). The forward current is exponentially related to the forward bias voltage, and the extracted ideality factors show distinct transport mechanisms in high and low positive regions. The leakage current increases with increasing reverse bias voltage, and the breakdown voltage decreases with decrease temperature, a consequence of tunneling effects because the leakage current at low temperature is larger than that at high temperature. The determined built-in potentials are 0.37 V in the low bias region, and 0.11 V in the high bias region, respectively. The results show the importance of temperature and applied bias in determining the electrical transport characteristics of all-perovskite oxide heterostructures.

Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a BaTiO3 coating layer with ~ 9 μm thickness is fabricated using an aerosol deposition method on (100) and (110) cut SrTiO3 single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and 1,300℃ for 5 h). BaTiO3 layer shows different growth behavior and X-ray diffraction depending on cutting direction of SrTiO3 seed. Rectangular pillars at SrTiO3 (100) and laminating thin plates at SrTiO3 (110), respectively, are observed.

V-substituted SrTiO3 thermoelectric oxide materials were fabricated by the conventional solid state reaction method. From X-ray diffraction pattern analysis, it can be clearly seen that almost every vanadium atom incorporated into the SrTiO3 provided charge carriers. The electrical conductivity σ, Seebeck coefficient S, and thermal conductivity k were investigated in a high temperature regime above 1000 K. The addition of vanadium significantly reduced the thermal conductivity and enhanced the Seebeck coefficient, as well as the electrical conductivity, thus enhancing the ZT value. A maximum ZT value of 0.084 at 673 K was observed for the sample with 1.0 mole% of vanadium substitution. In this study, the reason for the enhanced thermoelectric properties via vanadium addition was also investigated.

New lead-free piezoelectric ceramics 0.96[{Bi0.5 (Na0.84 K0.16)0.5}1-xLax(Ti1-y Nby)O3]-0.04SrTiO3 (BNKT-ST-LN, where x = y = 0.00 ≤ (x = y) ≤ 0.015) were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature (Tm) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization (33 C/cm2) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.

8 mol% Y-doped powder was synthesized by Pechini method from titanium isopropoxide, strontium nitrate, yttrium nitrate, citric acid and ethylene glycol. A pyrochlore phase-free perovskite powder was obtained by calcining a polymeric resin, which was prepared from a precursor solution, at in an air atmosphere. Low temperature calcination could lead to a fine-grained microstructure. In the case of a solid-state reaction, an extended heat-treatment at high temperature in a reduced atmosphere needed to obtain a single phase perovskite .

Field emission display(FED) is actively investigated in view of the development of full color flat-panel display, which can replace some cathode-ray tube(CRT). Thus, the development of new phosphors appropriate for FED is urgently needed and has been actively investigated. In this work, SrTiO3:Pr3+ phosphor was prepared by sol-gel method and the coating was applied by sol-gel method combined with sonication on these phosphor's surface into diluted precursor solution. It was found that very fine particles of coating material were formed on phosphor's surface. The luminescent intensity of SrTiO3:Pr3+ phosphor coated with SiO2 and Al2O3 was considerably increased without any noticeable change in color chromaticity. The optimum concentration of coating material was found to be 1wt% and the optimum pH value of the solution was 10.

본 연구에서는 부분산화한 Ti 분말을 첨가한 BaTiO3계 세라믹스를 진공중 1350˚C에서 1 h 소결하여 제조하였다. 공기중 가열후 전기적 성질과 미세조직에 미치는 부분산화한 Ti분말 첨가량의 효과를 조사하였다. 그 결과, 5~7vol%의 부분산화한 Ti분말을 첨가한 반도성 BaTiO3계 세라믹스는 비정항의 변화크기가 105이상인 우수한 PTCR 특성을 나타내었고 또한, 고다공질과 미립화된 조직을 얻을 수 있었다. 5 vol%의 부분산화한 Ti 분말을 첨가한 BaTiO3계 세라믹스의 상대밀도와 입도는 각각 54%, 1.3 μm였다. 부분산화한 Ti 분말의 첨가에 의한 BaTiO3계 세라믹스의 PTCR 특성 발현은 입계에서의 산소 흡착에 기인하였는데, 이는 Heywang모델로써 설명할 수 있었다.

Ar 이온 식각법을 이용하여 (001) SrTiO3(STO) 단결정 기판 위에 200nm 높이의 계단형 모서리를 제작하였다. 계단식은 입사하는 Ar 이온 빔에 대한 Ar 이온 입사각과 마스크 회전각을 조절함으로써 38˚-70˚의 넓은 범위로 제어할 수 있었다. 초전도 YBa2Cu3O7-δ박막은 계단이 있는 STO 기판 위에 펄스레이저 증착법을 이용하여 증착하였으며, 박막의 두께는 계단 높이에 대한 박막의 두께비가 0.5-1.2가 되도록 하였다. 계단형 모서리 조셉슨 접합의 임계전류밀도와 IcRn값은 77K에서 각각 104A/cm2, 70-200μV이었다.

고상반응법으로 SrTiO3 : AI, Pr 적색 형광체를 합성하였다. PL 스펙트럼과 CL 스펙트럼의 발광 강도를 소결 온도와 소결 시간등의 형광체의 제조 변수에 대하여 최적화 하였다. 열처리한 분말은 XRD 분석 결과 페로브스카이트구조를 보였고, PSD 분석결과 평균입자크기는 약 3~5μm이었다. 또한 분말의 주사 전자 현미경 사진에 의한면 구형을 갖는잘 결정화된 입자들이 관찰되었다. 특히, 본 연구에서 합성된 분말의 특성은 상용화된 Y2O3: Eu 형광체 보다 저전압에서의 CL 특성이 더 우수하였으며, 이 형광체는 저전압에서 구동하는 FED에 응용할 가능성이 높을 것으로 생각된다.