• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.1850-1852
• /
• 2005

$SrTiO_3$ and $BaTiO_3$ sol-liquids and powders were prepared by the sol-gel method. $SrTiO_3/BaTiO_3$ heterolayered thin/thick films have been prepared on the $Al_2O_3$ substrates by screen printing and spin-coating method. The thin films were sintered at $750^{\circ}C$ in the air for 1 hour and the thick films sintered at $1325^{\circ}C$ in the air for 2 hours, respectively. The $SrTiO_3/BaTiO_3$ thin/thick films's structural and dielectric properties were investigated. Increasing the spin-coating times, (110), (200), (211) peaks of the $SrTiO_3$ were increased. The X-ray diffraction(XRD) patterns and SEM photographs indicated that the $SrTiO_3$ phase were formed in the surface of $BaTiO_3$ thick films. The average thickness of a $BaTiO_3$ thick films and $SrTiO_3$ thin films were $50{\mu}m$ and 400nm, respectively The dielectric constant and dielectric loss of the $SrTiO_3/BaTiO_3$ thin/thick films with $SrTiO_3$ coated 5 times were 1598 and 0.0436 at 10KHz.

• Analytical Science and Technology
• /
• v.6 no.2
• /
• pp.239-246
• /
• 1993

The structure of $(BaSr)TiO_3$ thin film deposited on ITO coated glass, bare glass and (100) Si substrates was not changed, but the crystallinity was improved by the polycrystalline ITO layer and (100) Si substrate. The composition of $(BaSr)TiO_3$ thin film deposited on ITO coated glass was nearly stoichiometric ((Ba+Sr)/Ti=1.08~1.09) and very uniform through all deposition process. But as the deposition temperature increases, the interdiffusion between grown thin film and ITO layer and between ITO layer and base glass is severer. $(BaSr)TiO_3$ thin film deposited on ITO coated glass substrate was highly transparent. The refractive index($n_f$) of $(BaSr)TiO_3$ thin film deposited on ITO coated glass was 2.138~2.286 as a function of substrate temperature.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.5
• /
• pp.210-213
• /
• 2005

The $BaTiO_3/SrTiO_3$ 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 $BaTiO_3/SrTiO_3$ thick films has been investigated. The relative dielectric constant and dielectric loss at 1 MHz of the $BaTiO_3/SrTiO_3$ heterolayered thick films with sintering temperature of $1350^{\circ}C$ were about 751 and 1.74, respectively. The remanent polarization $(P_r)$ of the pure $(Ba_{0.5}Sr_{0.5})TiO_3$ and $BaTiO_3/SrTiO_3$ heterolayered films are approximately $5.1\;{\mu}C/cm^2$ and $10\;{\mu}C/cm^2$. This study suggests that the design of the $BaTiO_3/SrTiO_3$ heterolayered thick films capacitor with different phase should be an effective method to enhance the dielectric and ferroelectric performance in devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.9
• /
• pp.825-828
• /
• 2008

$Sr_xBa_{(1-x)}TiO_3$ red phosphors doped with Pr(0.13 mol%) and Al(O.23 mol%) were synthesized by solid state reaction method. Orthorhombic perovskite structure with increasing value of x in $Sr_xBa_{(1-x)}TiO_3$:Pr,Al phosphors changed to cubic perovskite structure. Emission bands at 615 nm and 492 nm in $Sr_{0.25}Ba_{0.75}TiO_3$:Pr,Al and $BaTiO_3$:Pr,Al phosphors were observed at room temperature. The main cause of green luminescence at 492 nm was explained by the change of the 4f5d band.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.609-612
• /
• 2002

In this study, the electrical properties were investigated for the deposited Ba,Sr)(Nb,Ti)$O_3$[BSNT] thin films grown on $Pt/TiO_2/SiO_2/Si$ substrate by RF sputtering method. The structural properties of the BSNT thin films affected by the $Ar/O_2$ rates were investigated. In the case of the BSNT thin films deposited with condition of 60/40$(Ar/O_2)$ ratio, the $BaTiO_3$, $SrTiO_3$ and $BaNbO_3$ phases were showed. The composition ratio of Nb and Ti in the BSNT thin films were nearly equivalent. Also, in the BSNT thin films deposited with condition of 60/40 and 80/20$(Ar/O_2)$ ratios, the composition of Ba, Sr, Nb and Ti were relatively uniform. The Ba, Sr, Nb and Ti in the BSTN thin films were not diffused into the Pt layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.4
• /
• pp.317-321
• /
• 2003

In this study, the structural properties were Investigated for the deposited (Ba,Sr)(Nb,Ti)O$_3$[BSNT] thin films grown on Pt/TiO$_2$/SiO$_2$/Si substrate by RF sputtering method. The structural properties of the BSNT thin films affected by the Ar/02 ratios were Investigated. In the case of the BSNT thin films deposited with condition of 60/40(Ar/O$_2$) ratio, the BaTiO$_3$, SrTiO$_3$ and BaNbO$_3$ phases were showed. The composition ratio of Nb and Ti in the BSNT thin films were nearly equivalent. Also, in the BSNT thin films deposited with condition of 60/40 and 80/20(Ar/O$_2$) ratios, the composition of Ba, Sr, Nb and Ti were relatively uniform. The Ba, Sr, Nb and Ti in the BSTN thin films were not diffused into the Pt layer.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.55-55
• /
• 2003

Ferroelectric 물질은 고유전성, 자발분극과 전기장에 따른 유전상수의 변화 등의 특성을 가지고 있으므로 많은 연구가 진행중이다. 이러한 ferroelectric 물질의 유전 특성에 미치는 요소로는 물질의 조성비, 박막의 스트레스, 결정성 등이 있다. 특히 스트레스에 대한 연구가 활발히 진행중이다. 본 연구에서 산화물 인공격자를 이용하여 단일박막에서 얻을 수 없는 격자변형도를 얻어 격자 변형이 박막의 유전특성에 미치는 영향을 연구하였다. BaTiO$_3$ (BTO)/SrTiO$_3$ (STO) 산화물 인공격자를 Pulsed laser deposition (PLD)법으로 (La,Sr)CoO$_3$ 전극이 코팅된 MGO (100) 단결정 기판위에 증착시켰다. 적층 주기에 변화를 주어 BTO와 STO 각각 1.01~1.095와 0.925 ~ 1.003의 단일 막에서는 얻을 수 없는 격자 변형도를 얻었다. 이 실험적 데이터를 기초로 하여 density functional theory (DFT)라고 불리는 범함수밀도론를 기초한 제일원리적 계산 방법을 통하여 격자 변형된 SrTiO$_3$의 구조적, 전기적 특성을 계산하였다. SrTiO$_3$와 BaTiO$_3$ 격자의 안정성을 분석하기 위하여 Vienna Ab-intio Simulation Package (VASP) code가 사용되었다. SrTiO$_3$와 BaTiO$_3$ 산화물 격자의 안정성 분석 후, frozen-phonon 계산 방법을 사용하여 zone-centered optical phonon mode가 계산되었으며, mode effective charge는 Berry-phase polarization 으로부터 얻어졌다. SrTiO$_3$ 격자가 격자변형이 일어나지 않은 상태로부터 c/a= 0.985로 격자 변형 이 일어남에 따라 optical phonon mode는 점차 hardening되었다. BaTiO$_3$ 격자의 경우 SrTiO$_3$ 격자와는 달리 격자 변형이 1.01~1.023으로 진행됨에 따라 optical phonon mode의 증가를 가져왔으나 Born effective charge의 증가하였으며, 더 이상 격자 변형이 진행됨에 따라 optical phonon mode의 감소를 가져왔으나 Born effective charge의 증가 유전상수는 증가했다. 격자 변형이 SrTiO$_3$ 와 BaTiO$_3$ 산화물 격자의 optical phonon mode와 Born effective charge에 크게 영향을 미쳤다.

• Journal of the Korean Ceramic Society
• /
• v.23 no.1
• /
• pp.27-32
• /
• 1986

This study is aimed at synthsizing high dielectric material (Ba, Sr)$TiO_3$ through direct wet process. Pure and ultra fine particle of (Ba, Sr)$TiO_3$ Powder was synthesized from $BaCl_2$ $SrCl_2$ and TiCl4 aqeous solution at KOH Solution in the $N_2$ gas atmosphere. $BaCl_2$ $SrCl_2$ and TiCl4 were Mixed with the mole ratio of 1:9, 3:7:10, 5:5:10, 7:3:10, 9:1:10 and sythesized at 4$0^{\circ}C$~9$0^{\circ}C$ for 10min~15hrs. The particle size particle shape crystallinity and synthesis condition of (Ba, Sr)$TiO_3$ powder with the variation of temperature and reaction time in the aqueous solution studied by the exprimental instruments of DTA. TGA, X-ray diffratometer SEM.

• Electrical & Electronic Materials
• /
• v.10 no.7
• /
• pp.674-681
• /
• 1997

Ternary compound ceramics, (1-y-x) BaTiO$_3$-y SrTiO$_3$-x MgTiO$_3$(0.00 x 0.20), were fabricated by the conventional ceramic process. The structural and dielectric properties of specimens were investigated while varying the composition and sintering temperature(1,200~1,45$0^{\circ}C$) in order to obtain the optimum condition of capacitor. As is well known, Curie temperature(T$_{c}$) of high dielectric-based ceramic(BaTiO$_3$) was shifted and temperature of capacitance was decreased in according to increase of solid solution with (Sr, Mg)TiO$_3$. As a result, a suitable condition of compound rate for capacitor was obtained such as the BSM-11(0.8BaTiO$_3$-0.1SrTiO$_3$-0.1MgTiO$_3$), and sintering temperature was sintered at 1,25$0^{\circ}C$ for two hours. In this case, dielectric constant<1,300, dielectric loss(tan$\delta$)<0.03, and the variation rate of capacitance had less than 3% in the range -10~7$0^{\circ}C$.>.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.795-797
• /
• 1998

A $BaTiO_3$, ferroelectric material, was mixed $SrTiO_3$, $(x)BaTiO_3-(1-x)SrTiO_3$($0.7{\leq}x{\leq}1$) ceramic capacitor with stable electrical properties in high voltage was fabricated. And microstructure, electrical property were investigated with $SrTiO_3$ mol ratio. The shrinkage, open porosity, sintering density were predominated at $9BaTiO_3-0.1SrTiO_3$. Increasing $SrTiO_3$ mol ratio, curie temperature was shifted at low temperature and maximum permittivity was increased. Also, $0.9BaTiO_3-0.1SrTiO_3$ was showed stable dielectric properties at $25{\sim}80[^{\circ}C]$. V-I properties of specimen were observed in the temperature range of $21{\sim}143[^{\circ}C]$, were divided into three regions. The region I below 10[kV/cm] was shown Ohmic conduction, the region II from 10 to 30[kV/cm] was explained by the Poole-Frenkel emission theory and the region III above 30[kV/cm] was analysed by the tunneling effect.