• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 춘계 학술발표 강연 및 논문 개요집
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• pp.113-113
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• 1994

• 한국세라믹학회지
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• 제28권9호
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• pp.689-695
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• 1991

Dielectric properties of Ba1-$\chi$Sr$\chi$Ti1-yCayO3-y ceramics, where Sr and Ca were doped to Ba-site and Ti-site within the range of 0 x 0.24 and 0 y 0.05, respectively, were investigated. The substitution of Ca for Ti, which maintained the high resistivity of these formulations after sintering in a reducing atmosphere, was confirmed. Ca addition decreased the tetragonality c/a, increased the unit cell volume, and lowered Curie temperature, which were attributed to the occupancy of Ca2+ ions on Ti-sites. The lowering of Curie temperature by Ca addition was affected by the substitution of Sr for Ba-site; within 2 mol% of Ca, Curie temperature was lowered at a rate of 2$0^{\circ}C$ and 16$^{\circ}C$ per mol% of Ca at x=0 and x=0.08, respectively. Whereas the resistivity of the formulations without Ca was reduced to 107 {{{{ OMEGA }}cm, when sintered at low oxygen partial pressure of 10-9 MPa, the resistivity value higher than 1011 {{{{ OMEGA }}cm was maintained for the formulations containing Ca more than 0.5 mol%. Dielectric loss factor, tan$\delta$, was about 1% for most formulations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.51-54
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• 2000

In this paper, $Ba_{0.5}$Sr$_{0.5}$TiO$_3$ thin films were prepared on Pt/Ti/SiO$_2$/Si substrate by RF magnetron sputtering method. We investigated effect of deposition conditions (especially RF input power) on structural properties of BST thin films. Deposit conditions of BST films were set working gas ratio, Ar:O$_2$= 70 : 30, working pressure 10mTorr, and RF input power 25W, 50W, 75W and 100W. Post-annealing using rapid thermal annealing(RTA) performed at 45$0^{\circ}C$, 55$0^{\circ}C$, $650^{\circ}C$, and 75$0^{\circ}C$ in oxigen ambient for 60 sec, respectively. The structural properties of BST films on Pt/Ti/SiO$_2$/Si substrate analysed by X-ray diffraction(XRD).).).

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.20-20
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• 2001

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.52-55
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• 2000

In this study, (Ba,Sr)$TiO_3$(BST) thin films were etched with a magnetically enhanced inductively coupled plasma(MEICP) as a function Ar/$CF_4$ gas mixing ratio. Experiment was done by varying the etching parameters such as rf power, dc bias voltage and chamber pressure. The maximum etch rate of the BST films was 1700 ${\AA}/min$ under $CF_4/(CF_4+Ar)$ of 0.1, 600 W/350 V and 5 mTorr. The selectivity of BST to Pt and PR was 0.6, 0.7, respectively. X -ray photoelectron spectroscopy(XPS) studies shows that there are surface reaction between Ba, Sr, Ti and C, F radicals during the etching. To analyze the composition of surface residue remaining after the etching, films etched with different $CF_4$/Ar gas mixing ratio were investigated using XPS.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.141-144
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• 2011

We report the synthesis of $SrTiO_3$, $BaTiO_3$ and $Ba_xSr_{1-x}TiO_3$ (BST) nanoparticles (NPs) in various compositions (x = 0.25, 0.5 and 0.75) by an inorganic sol-gel method under a basic condition. Highly crystalline nanoparticles were formed at the reaction temperature of 25 - $100^{\circ}C$ from a stabilized titanium alkoxide in tetramethylammonium hydroxide (TMAH) and barium or strontium acetate in aqueous solution. Morphology and particle structure of the synthesized BST NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BST nanoparticles in various compositions were monodispersed without mutual aggregation, and their average sizes were in the range of 70 - 80 nm. Furthermore, they showed highly crystallized perovskite phase over the whole composition range from $SrTiO_3$ to $BaTiO_3$. We also proposed a mechanism for the low-temperature formation of BST NPs.

• 센서학회지
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• 제19권2호
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• pp.155-159
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• 2010

0.96$(Na_{0.5}K_{0.5})NbO_3$-0.04$(Ba_{(1-x)}Sr_x)TiO_3$ lead free piezoelectric ceramics were synthesized to enhance the piezoelectric properties of (Na,K)$NbO_3$. The systhesis and sintering method were the conventional solid state reaction method and general sintering method in air atmosphere. The polymorphic phase transition(PPT) was observed at all composition(0 $\leq$ x $\leq$ 0.05) when $(Ba_{(1-x)}Sr_x)TiO_3$ were added in the $(Na_{0.5}K_{0.5})NbO_3$. As Sr concentration was increased, grain size, dielectric loss(tan$\delta$) and mechanical quality factor($Q_m$) were decreased and piezoelectric constant($d_{33}$) and electromechanical coupling factor($k_p$) were increased within a limited value. The optimized piezoelectric and properties, $d_{33}$, $k_p$, $Q_m$, and tand, of 0.96$(Na_{0.5}K_{0.5})NbO_3$-0.04$(Ba_{(1-x)}Sr_x)TiO_3$ were 139 pC/N, 0.31 %, 95, 0.04 at the composition of x=0.04.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.129.1-129.1
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• 2000

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.309-313
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• 1997

(Ba$_{x}$Sr$_{l-x}$)TiO$_3$(BST) thin fi1ms with various Ba/Sr ratios were deposited on Pt(80nm)/SiO$_2$(100nm)/Si by RF magnetron sputtering. BST thin films which have x=0.6, 0.5, 0.4 were studied dielectric properties with temperature variation. The frequency was used from 100Hz to 1MHz for measuring dielectric constant. The measurement conditions of dielectric constant with Temperature Variation were 1KHz and 2$0^{\circ}C$. As a result, the dielectric constant of BST thin film was about 425 and loss factor was 0.013. Also, with increasing Temperature, the dielectric constants of BST thin films were gradually decreased.sed.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.427-430
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• 2008

BaTiO3 and SrTiO3 thin films were fabricated on Pt/Ti/SiO2/Si substrate by the pulsed laser deposition process. The dependence of the deposited film quality upon the partial oxygen pressure during the deposition process was importantly examined. Regardless of the oxygen pressure, the as-deposited films were not fully crystallized. However, the film deposited at low oxygen pressure became well crystallized after the annealing process. It was concluded, therefore, that the partial oxygen pressure is reduced as low as possible during the deposition process and then anneal the as-deposited samples at ambient pressure to fabricate the well crystallized SrTiO3 and BaTiO3 films by laser ablation.