• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.133-135
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• 2005

Mn-Co-Ni-O계를 적용한 적층 칩 NTC 써미스터의 소성온도 및 냉각 조건에 따른 전기적 특성을 연구하였다. 특히, 소결조건에 따른 저항, B-정수의 경시 변화 특성으로부터 제품의 신뢰성 측면을 검토하였다. 소결온도 및 시간에 의한 영향보다는 냉각속도에 따른 초기 저항 및 B-정수의 변화가 크게 나타났으며 냉각속도를 조절한 시편에서 경시변화율은 1%이하인 특성을 얻을 수 있었다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.11a
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• pp.38-38
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• 2004

• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.994-1000
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• 2000

Mn-Ni-Co계 스피넬을 모재로 선택하여 상업용 페라이트 등 다양한 종류의 Fe-스피넬과 동시 소결 가능성을 검토할 목적으로 각 소재의 소결 거동, 서미스터와의 계면 반응이나, 2차상의 형성 등에 대해 알아보았다. 대부분의 페라이트 조성이 Mn 스피넬과 새로운 2차상을 형성하지는 않는 것을 알 수 있었다. 상업용 페라이트의 경우 115$0^{\circ}C$ 소결 온도에서 접합이 가능한 조성은 다량의 액상이 존재하며 접합계면의 폭이 상대적으로 넓으므로 서미스터 특성에도 좋지 않은 영향을 줄 수 있을 것으로 생각된다. 반면에 MFN1과 MFN2 조성은 접합계면에서 새로운 2차상이 형성되지 않고 원소의 상호확산도 작아 NTC 서미스터의 동시소결용 보호재로서의 가능성이 높은 것으로 확인되었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.128-131
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• 1997

기본 조성식 M $n_{1-x}$/F $e_{2+x}$/ $O_4$(이하 Mg계), M $n_{1-x}$/F $e_{2+x}$/ $O_4$(이하 Mg계)의 식에서 x를 0.0,0.025,0.1,0.2로 변화시키고, 하소온도 80$0^{\circ}C$, 소결은도를 l10$0^{\circ}C$~12$50^{\circ}C$로 $50^{\circ}C$간격으로 변화 시켰을 때와 Mn계와 Mg계를 1:1로 흔합하였을 때, F $e_2$ $O_3$의 과잉 양이 증가할수록 비저항은 감소하였고, 저항온도계수 $\alpha$는 밀도와 비례하는 관계를 나타내었으며, B정수는 4600(K)에서 10500(K)의 범위를 나타내었다. 본 조성의 실험으로써 Mn-Ni-Co계 서미스터의 대체가 가능함을 확인할 수 있었다.있었다.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1174-1179
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• 2001

Mn-Co-Ni oxide system has been used as the NTC thermistors for normal temperature applications. Mn-Co-Ni oxide-based thermistors with various compositions were sintered at 1250$^{\circ}C$ for 3 hours and then maintained at 1000$^{\circ}C$ for 3 hours. The electrical properties of the thermistors fabricated were measured. In particular the MCN622 composition (Mn$_3$O$_4$60 wt%, Co$_3$O$_4$20 wt%, NiO 20wt%) exhibited the lowest resistivity and relatively high B constant. The MCN721 composition (Mn$_3$O$_4$70wt%, Co$_3$O$_4$20wt%, NiO 10 wt%) showed the higher resistivity than any other compositions. The aging properties of each composition showed comparatively stable characteristics within ${\pm}$2%.

• The Journal of Engineering Research
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• v.5 no.1
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• pp.63-72
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• 2004

The properties of electrical resistance of Mn-Co-Ni-Fe oxide-based thermistor with various Fe contents in sintering process at $1200^{\circ}$ to $1400^{\circ}C$ for 4 hours in air atmosphere for fabricating thermistor materials were investigated. The results were as follows: all samples showed single cubic spinel crystal structures in all region. The electrical conductivity is the highest thermistor sintered at $1300^{\circ}C$ for 4 hours. In general when the Fe content is increased except F-2, the resistivity increases and relatively the conductivity decreases. Particularly F-2 composition exhibited the highest electrical conductivity (1.4${\times}$$10^-3$${\textohm}cm) and relatively low B constant(2906K)

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.424-428
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• 1998

Mn-Ni oxide thin films for NTC thermistor application were deposited on alumina substrates by using rf magnetron sputter. Effects of various substrate temperatures and annealing temperatures on the microstructure. crystal phase, resistivity and B constant were investigated. Microstructure of the films deposited below 178$^{\circ}C$ was fibrous microcrystalline and at 32$0^{\circ}C$and 40$0^{\circ}C$their microstructure was changed to columnar grain structure. After annealing at 90$0^{\circ}C$, the microstructure was transformed to equiaxed grain structure. Most of the phases were mixture of cubic spinel and $Mn_2O_2$ The crystal phase of the film deposited at 40$0^{\circ}C$ was changed to cubic spinel after annealing above 700"c. As the substrate temperature increased, the resistivity and B constant were greatly decreased, and these values become low and stable after annealing between $600^{\circ}C$and $700^{\circ}C$, All thin films deposited in the present study showed NTC thermistor characteristicsstics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.8
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• pp.584-592
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• 2012

Room temperature powder spray in vacuum process, so called Aerosol deposition (AD) is a room temperature (RT) process to fabricate thick and dense ceramic films, based on collision of solid ceramic particles. This technique can provide crack-free dense thin and thick films with thicknesses ranging from sub micrometer to several hundred micrometers with very fast deposition rates at RT. In addition, this technique is using solid particles to form the ceramic films at RT, thus there is few limitation of the substrate and easy to control the compositions of the films. In this article, we review the progress made in synthesis of piezoelectric thin/thick films, multi-layer structures, NTC thermistor thin/thick films, oxide electrode thin films for actuators or sensor applications by AD at Korea Institute of Materials Science (KIMS) during the last 4 years.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.455-462
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• 1996

Automobile Fuel Shortage Detecting Sensor, in this paper, was fabricated by using heat dissipation coefficient difference between gasoline and air condition the NTC thermistor of Mn-Ni Co system with the composition ratio of Mn$_{3}$O$_{4}$ : 9wt%, NiO : 28wt%, and CO$_{3}$O$_{4}$ : 61wt%. The condition of sensor operation is that, for turn-on characteristics, the time of arriving at 135mA must be less than 180 second when the DC voltage of 11V is applied in the air condition of -10.deg. C and that, for turn-off characteristics, the saturation current must be less than 60mA when the DC voltage of 15V is applied in the gasoline condition of 60.deg. C. It is known, from the experimental results, that the resistance range and B-constant for the Automobile Fuel Shortage Detecting Sensor with dimension of 5*3*0.9mm were 850-1150.ohm. and 1150-1250.deg. C, respectively and the resistance range and B-constant were agree with that of sensor operation condition. When Bi$_{2}$O$_{3}$ of 0-0.5wt% was added to Mn$_{3}$O$_{4}$ : 9wt%, NiO : 28wt%, and CO$_{3}$O$_{4}$ : 61wt% composition, the resistivity and B-value were 380-430(.ohm.-cm) and 1930 - 2030, respectively. Particularly, for Bi$_{3}$O$_{3}$ of 0.25-0.5wt%, the sintering density of over 90% and the operation characteristics necessary to Automobile Fuel Shortage Detecting Sensor were obtained. The difference of heat dissipation coefficient gasoline and air condition was 15 times.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.399-402
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• 2000

For improvement of B constant in $CaMnO_3$-$CaTiO_3$ perovskite type thermistors, effect of $Cr_2$$O_3$ addition ranged from 0.0wt% to 5.0wt% on electrical properties were investigated with contents and sintering temperatures in the view of crystal and microstructures. The solubility limit of Cr$_2$O$_3$was up to 0.5wt% judging from the result of lattice parameter. The grain size was decreased and the resistance at room temperature and B constant were increased with the addition of $Cr_2$$O_3$.On particular, B constant of$CaMnO_{3-x}$$Cr_2$$O_3$ system was increased greatly from 1574k to 2598k at 0.5wt% $Cr_2$$O_3$addition. Further addition of $Cr_2$$O_3$, however, resulted in the decrease of the resistance and B constant due to the $Cr_2$$O_3$ precipitation on the grain boundary. As the$CaTiO_3$contents increased in the $CaMnO_3$-$CaTiO_3$ system, the resistance at room temperature and B constant were highly changed.