• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.938-944
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• 1995

Dielectric properties and the stabilization of perovskite phase for the (1-y)Pb(Mg(1-x)/3Znx/3Znx/3Nb2/3)O3-yBaTiO3 ((1-y)PM1-xZxN-yBT) ceramics have been investigated as a function of amount of x and y. In the (1-y)PM0.6Z0.4N-yBT ceramics, the amount of pyrochlore phae was decreased by the addition of 2 mol% BT and the dielectric constant was increased. However, the dielectric constant decreased with further addition of BT even though pyrochlore phase was decreased. Dielectric prooperties in (1-y)PM0.6Z0.4N-yBT ceracmis were affected by the character of the BT rather than the amount of pyrochlore phase. The phase transitions were broadened and phase transition temperatures were lowered by the increase of BT contents.

• Korean Journal of Materials Research
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• v.2 no.2
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• pp.151-156
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• 1992

Using $Ba(OH)_2{\cdot}8H_2O, \;Sr(OH)_2{\cdot}8H_2O$ and $Ti(i-OC_3H_7)_4$, fine $(Ba_{1-x}, \;Sr_{x})TiO_3$ powders were synthesized through sol-gel process. The particle size of the powders calcined at $700^{\cric}C$ proved to be 20-40nm by the observation of TEM micrographs and measurement of BET specific surface area. The analysis of XRD patterns showed that the phase of the powders was cubic, and it was identified with the lattice parameters determined through XRD patterns and the shift of (112) peaks that the solid solution powders were synthesized. It was expected through the analysis of relative ratio of cations and the uniformity of compositions in the powders examined by EDAX analysis and relative dielectric constant measurements for sintered body that the distribution of cations was uniform in particle unit.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.205-206
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• 2006

(BaSr)$TiO_3$ thick films were prepared by tape casting method, using $BaTiO_3$ and $SrTiO_3$ powder slurry in order to investigate dielectric properties. With MgO additives, the sintering density was 5.8 $g/cm^3$ and the BST sample exhibited the maximum dielectric constant, tunability at temperatures near phase transition point. Dielectric loss be on the decrease because the interface is not a pore. BST sample be applicable on tunable device.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.767-772
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• 1999

The effect of B2O3 addition on the sintering behavior dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 ceramics were investigated. The sample with 0.5wt% B2O3 was sintered under 115$0^{\circ}C$. The dielectric and ferroelectric properties of BST with 0.5wt% B2O3 was as good as BST without B2O3 sintered at 135$0^{\circ}C$ and its dielectric loss was even better When B2O3 was added over 1.0wt% the overdoped B2O3 remained in the specimens and formed a second phase which degraded the sintering behaivor dielectric properties of BST.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.336-336
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• 2008

A positive temperature coefficient of electrical resistivity (PTCR) was investigated in a ferroelectric lead-free perovskite-type compound $(Bi_{0.5}K_{0.5})TiO_3$ within $BaTiO_3$-based solid solution ceramics. The electrical properties and the microstructure of (1-x) $BaTiO_3$ - x $(Bi_{0.5}K_{0.5})TiO_3$ (BBKT) ceramics made using a conventional mixed and have been synthesized by an ordinary sintering technique. The Curie temperature was obviously increased with increasing of $(Bi_{0.5}K_{0.5})TiO_3$ content. The BKT ceramics (x=0.05) sintered at $1400^{\circ}C$ for 4h display low resistivity values of $10^1-10^2$ ohm cm at room temperature, PTCR effect(jump) of 1.05*$10^3$, and the Curie temperature of $T_c=141^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.175-182
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• 2022

Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO₃ for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO₃.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.20-20
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• 2001

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1275-1276
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• 2007

For fabrication of $BaTiO_3$ system Ferroelectric thick films, (Ba,Sr,Ca)$TiO_3$ (BSCT) powders, prepared by using the alkoxide-based sol-gel method, were doped $MnCO_3$ as acceptor and $Dy_{2}O_{3}$ as donor. $MnCO_3$ and $Dy_{2}O_{3}$-doped (Ba,Sr,Ca)$TiO_3$ thick films were fabricated by screen printing techniques on high purity alumina substrates. The structure and dielectric properties were investigated with variation of $Dy_{2}O_{3}$ amount. As a result of the differential thermal analysis(DTA), exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films, sintered at $1420^{\circ}C$ for 2h, showed the typical XRD patterns of perovskite polycrystalline structure and no pyrochlore phase was observed. The average grain size and thickness of specimens no doped with $Dy_{2}O_{3}$ was 1.32mm, 52mm, respectively. The relative dielectric constant decreased and dielectric loss increased with increasing amount of $Dy_{2}O_{3}$ dopant, the values of the BSCT thick films no doped with $Dy_{2}O_{3}$ were 4043 and 0.4% at 1 kHz, respectively. The relative dielectric constant gradually decreased in the measured frequency range from 0.1 to 100 kHz

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.81-87
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• 2005

The compositions for LTCC embedded capacitors based on $BaTiO_3$ ceramics with $5\~15\;wt\%$ of lithium-borosilicate glass frits were studied. After the glass frits, which is chemically stable and has acceptable ability of low-temperature sintering, were added to the host dielectric materials, the sintering behavior and dielectric properties were evaluated. As for $BaTiO_3$, relative density of >$95\%$, permittivity 990, and dielectric loss $3.1\%$ were obtained when sintered at $925^{\circ}C$ with 5 wt$\%$ of glass frits. As for $(Ba,Ca)(Ti,Zr)O_3$ ceramics, relative density of >$95\%$, open porosity <$0.5\%$, permittivity 700, and dielectric loss $2\%$ were obtained when sintered at $875^{\circ}C$ with 10 wt$\%$ of glass frits.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.56-56
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• 2003

BaTiO$_3$, SrTiO$_3$단일막과 BaTiO$_3$ (BTO)/SrTiO$_3$ (STO) 산화물 인공격자를 pulsed laser deposition (PLD) 법에 의해서 100 nm 두께의 (La,Sr)CoO3 (LSCO) 산화물 전극이 코핑된 MgO 단결정 기판 위에 증착시켰다. 이러한 기판위에서 2 unit cell의 적층 두께를 갖는 BTO/STO 초격자 (=BTO2/STO2)를 100～5 nm까지 변화시켰다. 또한 BTO와 STO 단일막도 같은 두께로 변화시켰다. 이러한 두께 범위에서 BTO, STO 단일막과 초격자의 격자변형에 따른 유전특성을 살펴 보았다. 두께 변화에 따른 단일막과 초격자의 구조 분석은 포항 방사광 가속기의 x-ray 회절에 의해서 이루어졌다. 다양한 두께를 갖는 BTO2/STO2 초격자에서 BTO와 STO 충은 in-plane 방향으로 격자정합을 유지하면서 변형되었다. 두께가 얇아지면서 하부 LSCO영향으로 BTO, STO의 n-plane 격자상수는 LSCO 격자상수 쪽으로 접근하였다. Out-of-plane 방향의 BTO 격자상수는 두께가 얇아지면서 증가하였고 반면에 STO 격자상수는 감소하였다. STO와 BTO 단일막의 격자변형은 두께가 얇아지면서 in-plane 방향으로 압축응력으로 인해 증가하였다. 그러나, 격자부정합도가 큰 BTO격자에서 더 많이 변형되었다. 또한 초격자에서 BTO격자가 BTO 단일막보다 더 많이 변형되었는데 초격자에서는 BTO, STO 두 층의 발달된 변형뿐만 아니라 하부 LSCO/MgO 기판의 영향을 함께 받고 있기 때문이다. 초격자와 단일막의 유전상수를 살펴보면은 두께가 감소하면서 유전상수가 감소하는 size effect을 보이고 있다. 하지만 초격자에서의 유전상수가 단일막보다 우수한 유전특성을 보이고 있다. 이러한 결과로 볼 때 격자변형이 size effect 영향을 끼치는 중요한 요소임을 확인하였다.