• 한국세라믹학회지
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• 제27권3호
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• pp.412-422
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• 1990

Porous SiC ceramics were proposed to be promising materials for high-temperature thermoelectric energy conversion. Throughthe thermoelectric property measurements and microstructure observations on the porous alpha SiC and the mixture of $\alpha$-and $\beta$-SiC, it was experimentally clarified that elimination of stacking faults and twin boundaries by grain growth is effective to increase the seebeck coefficient and increasing content of $\alpha$-SiC gives rise to lower electrical conductivity. Furthermore, the effects of additives on the thermoelectric properties of 6H-SiC ceramics were also studied. The electrical conductivity and the seebeck coefficient were measured at 35$0^{\circ}C$ to 105$0^{\circ}C$ in argon atmospehre. The thermoelectric conversion efficiency of $\alpha$-SiC ceramics was lower than that of $\beta$-SiC ceramics. The phase homogeneity would be needed to improve the seebeck coefficient and electrical conductivity decreased with increasing the content of $\alpha$-phase. In the case of B addition, XRD analysis showed that the phase transformation did not occur during sintering. On the other hand, AlN addiiton enhanced the reverse phase transformation from 6H-SiC to 4H-SiC, and this phenomenon had a great effect upon the electrical conductivity.

• 한국재료학회지
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• 제14권1호
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• pp.41-45
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• 2004

P-type $Bi_{0.5}$$Sb_{1.5}$ $Te_3$ thin films were deposited by the flash evaporation technique, and their thermoelectric properties and electronic transport parameters were investigated. The effective mean free path model was adopted to examine the thickness effect on the thermoelectric properties. Annealing effects on the carrier concentration and mobility were also studied, and their variations were analyzed in conjunction with the antisite defects. Seebeck coefficient and electrical resistivity versus inverse thickness showed a linear relationship, and the effective mean free path was found to be 3150$\AA$. No phase transformation and composition change were observed after annealing treatment, but carrier mobility increased due to grain growth. Carrier concentration decreased considerably due to reduction of the antisite defects, so that electrical conductivity decreased and Seebeck coefficient increased. When annealed at 473 K for 1 hr, Seebeck coefficient and electrical conductivity were $160\mu$V/K and 610 $W^{-1}$ $cm^{ -1}$, respectively. Therefore, the thermoelectric quality factor were also enhanced to be $16\mu$W/cm $K^2$.>.

• 대한금속재료학회지
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• 제50권11호
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• pp.839-845
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• 2012

The effect of an AlN additive on the thermoelectric properties of SiC ceramics was studied. Porous SiC ceramics with 48-54% relative density were fabricated by sintering the pressed ${\alpha}-SiC$ powder compacts with AlN at $2100-2200^{\circ}C$ for 3 h in an Ar atmosphere. In the undoped specimens, the Seebeck coefficients were positive (p-type semiconducting) possibly due to a dominant effect of the acceptor impurities (Al, Fe) contained in the starting powder. With AlN addition, the reverse phase transformation of 6H-SiC to 4H-SiC was observed during the sintering process. The electrical conductivity of the AlN doped specimen was larger than that of the undoped specimen under the same conditions, which might be due to a reverse phase trans-formation. The Seebeck coefficient of the AlN doped specimen was also larger than that of the undoped specimen. The density of specimen and the amount of addition had significant effects on the thermoelectric properties.

• 한국세라믹학회지
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• 제40권10호
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• pp.991-997
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• 2003

SiC세라믹스의 열전변환물성에 미치는 A1$_4$C$_3$ 첨가효과에 대해 연구하였다. $\alpha$-SiC 분말에 A1$_4$C$_3$를 첨가하여 Ar분위기 2100∼220$0^{\circ}C$에서 3시간 소결하여 상대밀도 47∼59%인 다공질 SiC세라믹스를 제조하였다. X-선 회절분석 및 주사형 전자현미경으로 소결체의 상조성과 미세구조를 분석하였으며, A1$_4$C$_3$ 첨가에 의해 6H에서 4H로의 상전이 발생을 관찰할 수 있었다. 전기전도도와 Seebeck 계수를 Ar 분위기 550∼95$0^{\circ}C$에서 측정하였다. 무첨가 시료의 경우 출발원료중에 함유된 p형 불순물(Al, Fe)에 의해 Seebeck 계수가 정(+)의 값을 나타내었으며, 소결온도가 증가함에 따라 전기전도도가 증가하였다. A1$_4$C$_3$ 첨가 시료의 전기전도도는 상전이 및 캐리어농도 증가에 의해 무첨가 시료보다 높았으며, 또 Seebeck 계수도 크게 나타났다. 시료의 밀도, 첨가량 및 소결조건이 열전변환물성에 크게 기여하였다.

• 한국세라믹학회지
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• 제40권11호
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• pp.1106-1112
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• 2003

$\beta$-FeSi$_2$의 열전물성에 있어서 산소의 역할을 규명하기 위해서, 고온상 ($\alpha$+$\varepsilon$)과 저온상 ($\beta$)-FeSi$_2$ 시료에 대해 산화처리에 따른 열전물성 측정 및 분석실험을 행하였다. 산화에 의해 소결밀도가 감소하였으며, 반도체상으로의 전이도 방해되었다. 모든 시료에서 도전율과 열전도율은 산화처리시간과 함께 감소하였다. 순수한 FeSi$_2$ 및 고온상 ($\alpha$+$\varepsilon$)을 산화처리한 시료 Seebeck 계수는 작은 양의 값을 나타낸 반면에, 저온상 ($\beta$)을 산화처리한 FeSi$_2$ 는 음의 값을 나타내었으며 약 500K 부근에서 최대값을 나타내었다. 또 산화시간과 함께 최대값도 증가하였다.

• Korean Chemical Engineering Research
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• 제49권2호
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• pp.263-270
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• 2011

본 논문의 목적은 리튬-암모니아 솔루션$(Li(NH_3)_n)$의 실험을 통하여 암모니아물질의 임계점인 $-40^{\circ}C$ 근처에서의 열전특성을 분석하고 이를 증명하는 것이다. 실험 결과 0.58 MPM~1.87 MPM을 갖는 리튬-암모니아 솔루션 $(Li(NH_3)_n)$ 은 온도차$({\Delta}T=0{\sim}15^{\circ}C)$에서 전류가 전압에 비례하는 열전전력을 발생시킨다는 사실을 확인하였다. 본 논문은 열전 물질 개발에 새로운 방향을 제시할 것이다.