• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.127-132
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• 2019

In this study, barium strontium titanate (BSTO) with high dielectric perovskite structure was synthesized by liquid-solid solution synthesis and the surface was modified using trimethylsilyl chloride (TMCS) as a silylation agent. Silylation surface modification is a method of reacting -OH ligand on the surface of BSTO nanoparticles with Cl in TMCS to generate HCl and replacing the ligand on the surface of nanoparticles with -Si, -CH₃. Silylation was optimized by varying the concentration of TMCS, and the structure of the silicon network was confirmed by Fourier-transform infrared spectroscopy. In addition, the crystallinity of BSTO nanoparticles was confirmed by X-ray diffractometer and the size of the nanoparticles was calculated using Scherrer equation. The field emission scanning electron microscopic image observed the change of the surface-modified BSTO particle size, and the contact angle measurement confirmed the hydrophobic property of the contact angle of 120.9° in the optimized nanoparticles. Finally, the surface-modified BSTO dispersion experiment in de-ionized water confirmed the hydrophobic degree of the nanoparticles.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.49-52
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• 2009

Barium strontium calcium titanate powders were prepared with the sol-gel method. Ferroelectric $(Ba_{0.54}Sr_{0.36}Ca_{0.1})TiO_3$(BSCT) thick films were fabricated by the screen-printing method on alumina substrate. Then we investigated the structural and dielectric properties of the BSCT thick films at different sintering temperatures. The thermal analysis showed that the BSCT polycrystalline perovskite phase formed at around $660^{\circ}C$. The X-ray diffraction analysis showed a cubic perovskite structure with no second phase present in all of the BSCT thick films. The average grain size and the thickness of the specimens sintered at $1450^{\circ}C$ were about $1.6{\mu}m$ and $45{\mu}m$, respectively. The relative dielectric constant increased and the dielectric loss decreased as the sintering temperature was increased; for BSCT thick films sintered at $1450^{\circ}C$ the values of the dielectric constant and the dielectric loss were 5641 and 0.4%, respectively, at 1 kHz.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.286-288
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• 2003

In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate $(Ba,Sr)TiO_3$ [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB $90^{\circ}$ branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.679-684
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• 1998

Dielectricand pyroelectric properties of {{{{ { { {Ba }_{0.67 }Sr }_{0.33 } }`TiO_{3 } ^{ } }} (BST) thin plates and films were investigated. For BST thin plates maximum dielectric constant and pyrolelectric coefficient were observed at around 24$^{\circ}C$ and pyroelectric characteristics were improved as applied bias field was increased. When the electric field of 4kV/cm was applied to the thin plates sintered at 140$0^{\circ}C$ the pyroelectric coefficients over 4$\times$10-7C/{{{{ { cm}^{2 }K }} were obtained in the range of 0-4$0^{\circ}C$ BST thin films deposited using rf magnetron sputtering showed [001] preferred orientation at substrate temperatures above 50$0^{\circ}C$ On the contrary to the thin plates the dielectric constants of the thin films gradually increased above 15$^{\circ}C$ and decreased as applied bias field in-creased. The pyroelectric coefficients of thin films were lower than 1/10 those of thin plates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.167-167
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• 2008

The barium strontium calcium titanate powders were prepared by sol-gel method. Ferroelectric $(Ba_{0.54}Sr_{0.36}Ca_{0.1})TiO_3$(BSCT) thick films were fabricated by the screen-printing method on alumina substrate. And we investigated the structural and dielectric properties of BSCT thick films with the variation of sintering temperature. As a result of thermal analysis, BSCT polycrystalline perovskite phase was formed at around $660^{\circ}C$. The results of X-ray diffraction analysis were showed a cubic perovskite structure without presence of the second phase in all BSCT thick films. The average grain size and the thickness of the specimen sintered at $1450^{\circ}C$ were about 1.6 mm and 45 mm, respectively. The relative dielectric constant increased and the dielectric loss decreased with increasing the sintering temperature, the values of the BSCT thick films sintered at $1450^{\circ}C$ were 5641 and 0.4% at 1kHz, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.402-405
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• 2001

$(Ba_{0.6-x}Sr_{0.4}Ca_{x})TiO_{3}$ (x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their stuctural and dielectric properties were investigated with variation of composition ratio and an amount of $Al_{2}O_{3}$ (0.5, 1.0, 1.5. 2.0, 3.0 wt%) doping content. As a result of the X-ray diffraction BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with increase an $Al_{2}O_{3}$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing an amount of $Al_{2}O_{3}$ doping content. The dielectric loss is minimum for BSCT doped with 1.5wt% $Al_{2}O_{3}$ content. The tunability was decreased with increasing an Ca content and is about 4.2% for BSCT(50/40/10) doped with 2.0wt% $Al_{2}O_{3}$ content.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.11
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• pp.550-554
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• 2001

$(Ba_{0.6}Sr_{0.4}Ca_x)TiO_3 + yAl_2O_3$ wt% (x=0.10, 0.15, 0.20, y=0~3.0) ceramics were fabricated by the mixed-oxide method, and their structural and dielectric properties were investigated with variation of composition ratio and $Al_2O_3$ doping content. As results of the X-ray diffraction and microstructure analysis, all BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with an increase of $Al_2O_3$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing $Al_2O_3$doping content. The dielectric loss is minimum at BSCT doped with 1.5wt% $Al_2O_3$content. The tunability was decreased with increasing an Ca content and the BSCT(50/40/10) specimen doped with 2.0wt% $Al_2O_3$content showed the maximum value of 4.2%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.304-310
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• 2003

(Ba$\sub$0.6-x/Sr$\sub$0.4/Ca$\sub$x/)TiO$_3$(BSCT) (x=0.10, 0.15, 0.20) powder, prepared by the sol-Bel method, were mixed with organic binder and then BSCT thick films were fabricated by the screen printing techniques on alumina substrates using the BSCT paste. The structural and the dielectric Properties were investigated for various composition ratio and sintering temperature. The second phase appeared in BSCT(40/40/20) thick film sintered at 1450$^{\circ}C$. BSCT thick film thickness, obtained by four printings, was approximately 110∼120$\mu\textrm{m}$. The Curie temperature and dielectric constant at room temperature were decreased with increasing Ca content. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) specimen, which was sintered at 1420$^{\circ}C$ and measured at 1MHz, were about 910, 0.46% and 9.28% at 5㎸/cm, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.402-405
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• 2001

(Ba$\_$0.6-x/Sr$\_$0.4/Ca$\_$x/)TiO$_3$(x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their structural and dielectric properties were investigated with variation of composition ratio and an amount of Al$_2$O$_3$(0.5, 1.0, 1.5, 2.0, 3.0 wt%) doping content. As a result of the X-ray diffraction BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with increase an Al$_2$O$_3$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing an amount of Al$_2$O$_3$ doping content. The dielectric loss is minimum for BSCT doped with 1.5wt% Al$_2$O$_3$ content. The tunability was decreased with increasing an Ca content and is about 4.2% for BSCT(50/40/10) doped with 2.0wt% Al$_2$O$_3$ content.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.311-312
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• 2006

The dielectric Properties of add $Li_2CO_3$ to ($Ba_{0.6}Sr_{0.4})TiO_3$ powder in this research, made thick film by tape casting method and annealing at $970^{\circ}C$ for 2 hours each from the $O_2$, Ar and O2-plasma atmosphere were investigated. The dielectric Properties of Ar atmosphere was to higher with tunability. The dielectric constant was increased and Curie temperature was shifted to higher temperature with increasing of annealing temperature.