• 한국세라믹학회지
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• 제43권7호
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• pp.421-426
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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 i.e. dielectric constant, ${\varepsilon}_r$, Curie temperature, $T_c$. Grain growth within $(BaSr)TiO_3$ thick films was observed with increasing weight ratio of $BaTiO_3$. This observation can be explained by phenomena of substitution of $Sr^{2+}$ ion for $Bi^{2+}$ ion in the $BaTiO_3$ system. Also, the Curie temperature in $(BaSr)TiO_3$ thick films was shifted to lower temperature range with increasing $ SrTiO_3$. Furthermore, Curie temperature having maximum dielectric constant was in the range of $-40^{\circ}C\;to\;30^{\circ}C$, and hence sharper phase transformation occurred at Curie temperature. There occurred decrease in tunability and k-factor of $(Ba_{0.6}Sr_{0.4})TiO_3$ calculated from the dielectric constant, ${\varepsilon}_r$ above Curie temperature. In addition, above the $60^{\circ}C$, phase fixation was observed. This means that internal stress relief occurred with increasing $90^{\circ}$ domains.

• E2M - 전기 전자와 첨단 소재
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• 제8권5호
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• pp.640-647
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• 1995

In this study, the BaTiO$\sub$3/ capacitor add to MnO$\sub$2/ like depressor and shifter were investigated for temperature or voltage compensation by structural and electrical analysis. The relative density of BCTM, generating poly crystall and formation of lattice defect, has a 90[%] over as the CaTiO$\sub$3/ come out to control grain size. The current density of BCTM2 increased non-ohmic in high-electric field but that BCTM3 and BCTM4 had a few changing. The BCTM3 and BCTM4 unformated grain boundary shown temperature compensation properties, so that the dielectric constant was low value. The curie point was near 140[.deg. C] in BCTM1 and BCTM4, but BCTM3 and BCTM4 not shown the curie point. It is found that the charging energy of BCTM4 was changed 6[%] according to rising temperature from room temperature to 417[K]. The formation of BaMnO$\sub$3/ was low dielectric constant to change frequency and temperature.

• 한국재료학회지
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• 제26권1호
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• pp.35-41
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• 2016

The electrical transport properties of $La_{0.5}Sr_{0.5}CrO_3$ below room temperatures were investigated by dielectric, dc resistivity, magnetic properties and thermoelectric power. Below $T_c$, $La_{0.5}Sr_{0.5}CrO_3$ contains a dielectric relaxation process in the tangent loss and electric modulus. The $La_{0.5}Sr_{0.5}CrO_3$ involves the transition from high temperature thermal activated conduction process to low temperature one. The transition temperature corresponds well to the Curie point. The relaxation mechanism has been discussed in the frame of electric modulus spectra. The scaling behavior of the modulus suggests that the relaxation mechanism describes the same mechanism at various temperatures. The low temperature conduction and relaxation takes place in the ferromagnetic phase. The ferromagnetic state in $La_{0.5}Sr_{0.5}CrO_3$ indicates that the electron - magnon interaction occurs, and drives the carriers towards localization in tandem with the electron - lattice interaction even at temperature above the Curie temperature.

• 한국화재소방학회논문지
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• 제21권4호
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• pp.65-71
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• 2007

본 논문에서는 PTC 서미스터의 전기적 특성과 온도특성을 이용하여 각종 전기화재 및 전기사고를 예방 보호하는 전기안전 제어장치에 대해 연구된다. PTC(Positive Temperature Coefficient) 서미스터는 온도변화에 따른 저항특성이 정(+)온도계수를 갖는 특징이 있다. 이러한 PTC는 정온도계수를 갖는 $BaTiO_3$계 세라믹스의 정방정계-입방정계 구조를 가지고 상변이점인 큐리(Curie)온도 이상으로 온도가 증가하면 저항이 급격히 증가하는 현상을 보인다. 본 논문에서는 이러한 정저항 온도특성과 자체 발열특성을 갖는 PTC 서미스터를 전기단락사고나 과부하사고 등의 전기사고의 감지센서로 이용하여 전기화재사고로부터 보호하는 제어시스템에 대해 제안한다. 그 결과 기존에 상용되는 차단기들의 빈번한 오동작과 비신뢰성, 저응답특성 등으로 발생되는 전기화재 및 전기재해의 문제점을 해결한다. 또한 제안한 전기안전장치는 다양한 실험결과를 통해 이론적 해석의 타당성이 입증된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.7-9
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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 and low temperature sintering. Sintering density was $5.7\;g/cm^3$ and the BST sample exhibited the maximum dielectric constant, tunability at temperatures near phase transition point. The dielectric constant was increased and curie temperature was shifted to higher temperature with increasing of annealing temperature.

• 한국자기학회지
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• 제5권5호
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• pp.380-382
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• 1995

The pressure dependence of the Curie temperature was determined in 2-dimensional like ferromagnet, MnAlGe up to a maximum pressure of 7.5 Gpa through measurements of electric resistance vs temperature curves. The pressure coefficient was positive with a considerably high rate of 9 K/GPa in the low pressure ragion, while it decreased gradually down to one order of magnitude smaller value at the maximum pressure. It was concluded that ther is an upper limit of about 550 K in the super-exchange type ferromagnetic interaction between Mn layers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.247-250
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• 1991

In this paper, we have investigated the poling conditons depending upon the electric field and temperature for PZT ceramics with various stoichiometry prepared by wet direct method, and $MnO_2$ dopant. The electric field required for saturation polarization was plotted against temperature $(1,000/T^{\circ}K)$ so that the required field could be estimated at any given temperature by measuring the charge displaced during poling. From this curve it should be possible to predict the field required to produce maximum domain switching at temperature below the Curie temperature, when $MnO_2$ dopant was added to the PZT ceramics, the electric field required for saturation polarization was lowered than that of undoped PZT samples.

• 한국세라믹학회지
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• 제32권1호
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• pp.1-10
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• 1995

Effects of calcination temperature on microstructure and electric-magnetic properties of Mg-ferrite were investigated. As the calcination temperature increase, the green density and the sintered density increase due to the enhancement of densification of calcined powder. The grain size in the sintered ferrite increases with increasing the calcination temperatures from 800 to 100$0^{\circ}C$, but decreases from 1000 to 120$0^{\circ}C$. The resistivity decreases with increasing the calcination temperatures from 800 to 110$0^{\circ}C$, but increases from 1100 to 120$0^{\circ}C$ due to the microstructure which consists of small, uniform grian size and pores at grain boundaries. Magnetization increases slightly due to the increasement of the sintered density while Curie temperature is almost constant regardless of calcination temperatures.

• 한국세라믹학회지
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• 제33권6호
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• pp.665-671
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• 1996

Ferroelectric Pb(Fe1/2Nb1/2)O3 thin films were successfully fabricated on ITO/Glass substrate by sol-gel proces-sing and characterized to determine the dielectric and electric properties. Viscosity of PEN sol measured to investigate rheological properties was 3.25 cP which was proper for coating. The sol also showed Newtonian behavior. RTA(Rapid Thermal Annealing) was used for the annealing of the thin film and 1200~1700$\AA$ thick PEN thin films were fabricated by repeating the intermediate and the final annealing. After the deposition of Pt as top electrode by vacuum evaporation dielectric and electric properties were measured. Dielectric properties of FFN thin film were enhanced by increasing the perovskite phase fraction with increasing the annealing temperature. Measured dielectric constant of 1700$\AA$ PFN thin film annealed at $650^{\circ}C$ was 890 at 1kHz Capacitatnce density and dielectric loss were 47 fF/${\mu}{\textrm}{m}$2 and 0.47 respectively. As a result of measuring Curie temperature PFN thin films had Curie point with a rang of 110~12$0^{\circ}C$ and showed broad dielectric peak at that point. Leakage current of the PFN thin films were increased with increasing the annealing tempera-ture.

• 마이크로전자및패키징학회지
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• 제15권1호
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• pp.51-58
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• 2008

본 논문에서는 PTC 서미스터의 전기적 온도특성을 이용하여 각종 전기화재 및 전기사고를 예방 보호하는 방재시스템에 대해 연구하였다. PTC(Positive Temperature Coefficient) 서미스터는 온도변화에 따른 저항특성이 정 (+)온도계수를 갖는 특징이 있다. PTC서미스터는 정온도계수를 갖는 $BaTiO_3$계 세라믹스의 정방정계-입방정계 구조를 가지고 상변이점인 큐리(Curie)온도 이상으로 온도가 증가하면 저항이 급격히 증가하는 현상을 보인다. 본 논문에서는 이러한 정저항 온도특성과 자체 발열특성을 갖는 PTC 서미스터를 전기단락사고나 과부하사고 등 전기사고의 감지센서로 이용하여 전기화재사고를 예방하는 제어시스템에 대해 제안하였다. 그 결과 기존에 상용되는 차단기들의 빈번한 오동작과 저 신뢰성, 저속응성 등으로 발생되는 전기화재 및 전기재해의 문제점들을 해결하였다. 또한 제안한 방재시스템의 다양한 실험결과를 통해 이론적 해석의 타당성을 입증하였다.