합성 조건에 따른 SrTiO3:Sm3+ 분말의 광 특성 연구

홍경수,양호순 한국물리학회 2013 새물리 Vol.63 No.1

Samarium-doped strontium titanate (SrTiO3:Sm3+) is synthesized by using the solid-state reaction method. The structure and the surface morphology of the synthesized powder are characterized, and the optical properties are studied by taking absorption, excitation, and emission spectra at room temperature. A red-orange luminescence corresponding to the 4G5/2 ! 6H7/2 transition of Sm3+ is observed. For operation with near ultraviolet excitation, SrTiO3:Sm3+ is found to be a red-orange emitting powder. The luminescence intensity is shown to vary with the doping rate of Sm3+ ions and the sintering time. 넓은 에너지 띠 간격을 갖는 perovskite 산화물인 SrTiO$_3$에Sm$^{3+}$이 첨가된 분말의 광특성을 연구하였다. 적색 형광을 내며분광학적 특성이 있어 중요한 활성체인 Sm$^{3+}$을 첨가한 SrTiO$_3$분말을 고상반응법으로 합성하였다. 합성된 시료의 물성과 표면 상태를조사하였으며, 분말 합성에 사용한 소결 시간 및 첨가된 Sm$^{3+}$이온의 농도에 따라 흡수, 여기 및 발광 스펙트럼을 측정하여 합성된분말이 갖는 광학적 성질을 알아보았다. 근자외선 여기에 의한 Sm$^{3+}$이온의 $^4$G$_{5/2}$ $\rightarrow$ $^6$H$_{7/2}$ 전이에 대응하는적-황색 형광이 관측되었다. SrTiO$_3$ 분말 합성에서 소결 시간과 발광세기와의 관계 및 Sm$^{3+}$ 이온의 농도가 발광의 세기에 미치는 영향을확인하여 광소재로 응용할 수 있음을 보였다.

$SrTiO_3$: $Pr^{3+}$,$Ga^{3+}$의 발광특성

변재동,이용제,장보윤,이현덕,유영문,류선윤 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.8

SrTiO$_3$에 Pr$^{3+}$ 이온, 또는 Pr$^{3+}$ 이온과 Ga$^{3+}$ 이온을 첨가하여 합성한 형광체와 floating zone method로 성장시킨 단결정의 PL 특성을 조사하였다. 분말 형광체와 단결정에서 모두 Ga$^{3+}$ 이온이 함께 첨가되었을 때 적색 발광 세기가 크게 증가하였다. XRF(X-Ray Fluorescence) 측정결과 Ga$^{3+}$ 이온이 함께 첨가되었을 때 SrTiO$_3$결정 격자내의 Pr$^{3+}$ 이온의 농도가 증가하였다. Ga$^{3+}$ 이온이 함께 첨가되었을 때 적색 발광 세기가 증가하는 것은 첨가된 Ga$^{3+}$ 이온이 결정내 발광 center인 Pt$^{3+}$ 이온의 농도가 증가시켰기 때문이며, 또한 Ga$^{3+}$ 이온이 hole trap center로 작용하기 때문인 것으로 생각된다.

Sm을 첨가한 SrTiO₃ 형광체의 발광특성

박창섭,유일,Park, Chang-Sub,Yu, Il 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.11

Photoluminescence properties of $SrTiO_3$:Sm red phosphors synthesized by solid state reaction method were studied under 254 nm excitation. Emission bands at 576 nm and 616 nm in heavily $Sm^{3+}$ ion doped $SrTiO_3$:Sm phosphors were observed, which were attributed to $^4G_{5/2}\rightarrow{^6}H_{5/2}$ and $^4G_{5/2}\rightarrow{^6}H_{7/2}$ transition of $Sm^{3+}$, respectively. The $Sm^{3+}$ ion concentration exhibiting the maximum emission intensity in the $SrTiO_3$:Sm was 30 mol%. The luminescence caused by $Sm^{3+}$ in the $SrTiO_3$:Sm phosphors was interpreted by the energy transfer between $Sm^{3+}$ ions.

LaAlO3 두께에 따른 LaAlO3/SrTiO3 계면에서의 전류-전압 특성을 이용한 전도성 변화 연구

문선영,장호원,김진상,백승협,강종윤,최지원,최헌진 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.8

Oxides possess several interesting properties, such as ferroelectricity, magnetism, superconductivity,and multiferroic behavior, which can effectively be used oxide electronics based on epitaxially grown heterostructures. The microscopic properties of oxide interfaces may have a strong impact on the electrical transport properties of these heterostructures. It was recently demonstrated that high electrical conductivity and mobility can be achieved in the system of an ultrathin LaAlO3 film deposited on a TiO2-terminated SrTiO3 substrate, which was a remarkable result because the conducting layer was at the interface between two insulators. In this study, we observe that the current-voltage characteristics exhibit LaAlO3 thickness dependence of electrical conductivity in TiO2-terminated SrTiO3. We find that the LaAlO3 layers with a thickness of up 3 unit cells, result in highly insulating interfaces, whereas those with thickness of 4 unit cells and above result in conducting interfaces. 에피택셜 성장한 산화물의 이종 접합 구조는 강유전성, 자성, 초전도 및 다강성과 같은 흥미로운 특성을 나타낸다. 산화물 계면에서의 미세 특성은 이종 접합 구조에서 전기적인 수송 특성에 큰 영향을 미칠 수 있다. 최근에 Ohtomo와 Hwang 그룹에서 TiO2-terminated SrTiO3 기판에 매우 얇은 두께로 LaAlO3가 증착 되었을 때, 두 물질 모두 부도체임에도 불구하고 계면에서 높은 전기 전도도와 전자 이동도가 발생하는 현상을 발견했다. 이러한 산화물 계면에서 전자는 4.2 K에서 최대 104 cm2V-1s-1의 높은 이동도를 가진다. 이 연구에서는 전류-전압 특성 분석을 이용하여 TiO2-terminated SrTiO3 기판에 증착되는 LaAlO3 박막 두께에 따른 전기전도도 의존성을 관찰하였다. 그 결과 LaAlO3층이 3 unit cells까지는 계면에서 부도체적인 성질을 유지하였다. 반면에 LaAlO3층이 4 unit cells 이상의 두께부터는 도체적인 성질의 계면을 얻을 수 있었다.

Fabrication of Novel n-SrTiO3/p-BiOI Heterojunction for Degradation of Crystal Violet Under Simulated Solar Light Irradiation

Yongmei Xia,Zuming He,Jiangbin Su,Ya Liu,Bin Tang,Xiaoping Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.6

Novel n-SrTiO3/p-BiOI heterojunction composites were successfully fabricated by loading SrTiO3 particles onto the surface of BiOI nanoflakes via a two-step method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-disperse X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS) and electrochemical measurements. The results show that the n-SrTiO3/p-BiOI heterojunction composites are composed of perovskite structure SrTiO3 and tetragonal phase BiOI. The composites exhibit excellent photocatalytic performance for the degradation of crystal violet (CV) solution under simulated solar light irradiation, which is superior to that of pristine BiOI and SrTiO3. The 30 wt.% SrTiO3/BiOI composite is found to be the optimal composite, over which the dye degradation reaches 92.5% for 30 min of photocatalysis. The photocatalytic activity of the 30 wt.% SrTiO3/BiOI composite is found to be 3.94 times and 28.2 times higher than that of bare BiOI and SrTiO3, respectively. The reactive species trapping experiments suggest that · O-2 and holes are the main active species responsible for the CV degradation. In addition, the electrochemical measurements elucidate the effective separation of photoinduced electron–hole pairs. Moreover, on the basis of experimental and theoretical results, a possible mechanism for the enhanced photocatalytic performance of the SrTiO3/BiOI heterojunction composites is also proposed.

SrTiO$_3$:Pr$^{3+}$,Ga$^{3+}$ Phosphor의 발광특성에 관한 연구

이미애,남산,김명호,서경수,변재동,Lee, Mi-Ae,Nahm, Sahn,Kim, Myong-Ho,Suh, Kyung-Soo,Byun, Jae-Dong 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.7

The effect of {{{{ {Ga }^{3+ } }} addition on the photoluminescence and cathodoluminescence of {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} was stu-died by performing the excitation emission and decay time measurements. Addition of {{{{ {Ga }^{3+ } }} in {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} resulted in a considerable enhancement of {{{{ { Pr}^{3+ } }} emission intensity. From the analysis of the experimental results the following mechanism is proposed. Excitation in the {{{{ {SrTiO}_{3 } }} host lattice leads to the formation of electrons in the conduction band and holes in the valence band. The electrons in the conduction band re-combine radiatively with the holes trapped at {{{{ { Ga}^{3+ } }} and the energy is transferred to {{{{ { Pr}^{3+ } }} ion which give its own characteristic red emission.

Synthesis of SrTiO3 Fibers and Their Effects on the Thermoelectric Properties of La0.1Dy0.1Sr0.75TiO3 Ceramics

Jiao Han,YiMing Zeng,Ying Song,HongQuan Liu 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.3

SrTiO 3 fi bers were fabricated by an in situ hydrothermal method using hydrated TiO 2 fi bers as both template and reactant. La 0.1 Dy 0.1 Sr 0.75 TiO 3 powders containing x wt.% SrTiO 3 fi bers ( x = 0, 1, 3, 5) were prepared by the sol–gel method andthen sintered at 1450 °C under a reducing atmosphere (N 2 /H 2 = 95/5). XRD analysis showed that the samples were mainlycomposed of SrTiO 3 phase and a few Dy 2 Ti 2 O 7 phase. TiO 2 phase was detected in the samples with x = 3 and x = 5, and itspeak intensity clearly reinforced with increasing x . With the addition of SrTiO 3 fi bers, the electrical conductivity increasedsignifi cantly and the Seebeck coeffi cient kept almost unchanged, resulting in a high power factor of 1015 μW m −1 K −2 at200 °C with a loading of 3 wt.% SrTiO 3 fi bers. Meanwhile, combined with low thermal conductivity, the sample with 3 wt.%SrTiO 3 fi bers showed the peak ZT value of 0.19 at 500 °C, which was 127% higher than that of La 0.1 Dy 0.1 Sr 0.75 TiO 3 .

The Dielectric Properties of BaTiO3/SrTiO3 Heterolayered Thick films by Screen Printing Method

Sung-Pill Nam,배선기,이성갑,이영희 한국전기전자재료학회 2005 Transactions on Electrical and Electronic Material Vol.6 No.5

The BaTiO3/SrTiO3 heterolayered thick films were fabricated by the screen printing method on alumina substrates. The effect of the sintering temperature on the microstructure and dielectric properties of the BaTiO3/SrTiO3 thick films has been investigated. The relative dielectric constant and dielectric loss at 1 MHz of the BaTiO3/SrTiO3 heterolayered thick films with sintering temperature of 1350 ˚C were about 751 and 1.74, respectively. The remanent polarization (Pr) of the pure (Ba0.5Sr0.5)TiO3 and BaTiO3/SrTiO3 heterolayered films are approximately 5.1 μC/cm2 and 10 μC/cm2. This study suggests that the design of the BaTiO3/SrTiO3 heterolayered thick films capacitor with different phase should be an effective method to enhance the dielectric and ferroelectric performance in devices.

Reduced graphene oxide/strontium titanate heterostructured nanocomposite as sunlight driven photocatalyst for degradation of organic dye pollutants

A. Rosy,G. Kalpana 한국물리학회 2018 Current Applied Physics Vol.18 No.9

Reduced graphene oxide/Strontium titanate (RGO/SrTiO3) heterostructured nanocomposite was synthesized by coupling Hummer's synthesized graphene oxide (GO) with hydrothermally synthesized SrTiO3 nanoparticles (SrTiO3) through a facile and unique high energy ultrasonication technique using triple solvents. XRD result confirmed the successful formation of pure, single phase and primitive cubic crystal structure RGO/SrTiO3 heterostructured nanocomposite. SEM result confirmed the successful intercalation of SrTiO3 nanoparticles over the two dimensional networks of RGO nanosheets. The synergistic and beneficial interactions between SrTiO3 and RGO resulted in smaller crystallite size (53 nm), reduced band gap (2.87 eV) and larger specific surface area (31m2/g) than that of as prepared pure SrTiO3 nanoparticles. RGO strongly influenced the photocatalytic activity of SrTiO3 and hence RGO/SrTiO3 heterostructured nanocomposite exhibited greater efficiency in degrading Rhodamine B (RhB) and Rose Bengal (RB) organic dye pollutants under natural sunlight irradiation than that of pure SrTiO3 nanoparticles.

Pr,Eu,Al을 첨가한 SrTiO₃ 형광체의 발광특성

박창섭,유일,Park, Chang-Sub,Yu, Il 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.6

[ $SrTiO_3$ ] red phosphors doped with Pr, Er and Al were synthesized by solid state reaction method. Three emission peaks in photoluminescence spectra of the $SrTiO_3:Eu$ Phosphors were observed at 583 nm, 610 nm and 685 nm. The emission peaks in the $SrTiO_3:Eu$ phosphors were associated with charge-transfer states. The decrease of photoluminescence intensity in $SrTiO_3:Eu,Al$ phosphors with doping Al ions was interpreted by the change of charge-transfer states.