• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.470.1-470.1
• /
• 2014

InAs는 high mobility를 갖는 III-V 화합물 반도체로 최근 InAs 나노선 기반 electronic transport에 대한 연구가 활발히 진행되고 있다. 또한, InAs는 n-type의 중온 영역대의 열전물질로서 나노선이나 나노박막과 같은 저 차원 구조의 열전 특성에 대한 보고가 이루어 지고 있다. 대부분의 InAs 나노선의 성장 방법은 화학기상증착법에 의한 것으로, 상온에서 $100{\mu}V/K$ 이하의 낮은 Seebeck 계수 값을 나타내고 있다. 본 연구는 무촉매 상태에서 MBE (Molecular beam epitaxy) 성장시킨 InAs 나노선의 열전 특성을 측정하였다. MTMP (Microfabricated Thermoelectric measurement platform)를 이용하여 50 K에서 300 K까지의 온도 영역에서 전기전도도, Seebeck 계수의 측정을 진행하였다. 그 결과 Seebeck 계수 값은 상온에서 대략 $200{\mu}V/K$로 높게 나타나고 있으며, 동일한 나노선의 상온 전기전도도는 대략 9800 S/m로 많은 보고들과 비슷한 수준의 수치가 나타나고 있다. Transconductance 측정을 통한 field-effect mobility와 carrier 농도를 평가한 결과가 Mott formula에서 계산된 carrier 농도와 유사한 결과를 나타내었다. 매우 큰 Seebeck 는 carrier 농도가 낮은 것에 기인한 것으로 판단된다.

• 대한금속재료학회지
• /
• 제46권5호
• /
• pp.315-320
• /
• 2008

The effect of Mn additive on the thermoelectric properties of Fe-Si alloys prepared by a RF inductive furnace was investigated. The electrical conductivity and Seebeck coefficient were measured as a function of temperature under Ar atmosphere to evaluate their applicability to thermoelectric energy conversion. The electrical conductivity of the specimens increased with increasing temperatures showing typical semiconducting behavior. The electrical conductivity of Mn-doped specimens are higher than that of undoped specimens and increased slightly with increasing the amount of Mn additive. This must be due to the difference in carrier concentration and the amount of residual metallic phase ${\varepsilon}$-FeSi(The ${\varepsilon}$-FeSi was detected in spite of 100 h annealing treatment at $830^{\circ}C$). And metallic conduction increased slightly with increasing the amount of Mn additive. On the other hand, Mn-doped specimens showed the lower Seebeck coefficient due to metallic phase. The power factor of Mn-doped specimens are higher than that of undoped specimens and would be affected by the electrical conductivity more than Seebeck coefficient.

• 대한금속재료학회지
• /
• 제47권12호
• /
• pp.860-865
• /
• 2009

The effect of Co additive on the electrical properties of Fe-Si alloys prepared by a RF inductive furnace was investigated. The electrical conductivity and Seebeck coefficient were measured as a function of the temperature under an Ar atmosphere to evaluate their applicability to thermoelectric energy conversion. The electrical conductivity of the specimens increased as the temperature increased, showing typical semiconducting behavior. The electrical conductivity of Co-doped specimens was higher than that of undoped specimens and increased slightly as the amount of Co additive increased. This is most likely due to the difference in the carrier concentration and the amount of residual metallic phase ${\varepsilon}$-FeSi (The ${\varepsilon}$-FeSi was detected in spite of an annealing treatment of 100 h at $830^{\circ}C$). Additionally, metallic conduction increased slightly as the amount of Co additive increased. On the other hand, Co-doped specimens showed a lower Seebeck coefficient due to the metallic phase. The power factor of Co-doped specimens was higher than that of undoped specimens. This would be affected more by the electrical conductivity compared to the Seebeck coefficient.

• The Korean Journal of Ceramics
• /
• 제2권1호
• /
• pp.11-18
• /
• 1996

The variation of electrical conductively and Seebeck coefficient of FeSi2 according to the density of the specimen has been observed over the temperature range 50 to $700^{\circ}C$. A conventional pressureless sintering method with various sintering time (0, 0.5, 1, 5h) at $1190^{\circ}C$ and/or various sintering temperatures(1160, 1175, 1190, $1200^{\circ}C$) for 2 h was carried out to prepare $FeSi_2$ specimens having various densities. The relationship between the electrical conductivity and Seebeck coefficient was investigated after two steps of annealing (at $865^{\circ}C$ and then $800^{\circ}C$ for total 160h) and thermoelectric measurement. The electrical conductivity for the specimens showed a typical tendency of semiconductor, the average activation energy of which in the intrinsic region (above $300^{\circ}C$) was observed approximately as 0.452 eV, and increased slightly with density. On the other hand, the specimen of the lower density showed the higher value of Seebeck coefficient in the intrinsic region. As the temperature fell into the non-degenerate region, the highly densified specimen which had relatively little residual metal phase showed the higher value of Seeback coefficient. The power factor of all specimens showed the optimum value at $200^{\circ}C$. However, the power factor of the specimen of the lower density increased again from $400^{\circ}C$ and that of the higher dense specimen increased from $500^{\circ}C$. The power factor was more affected by Seebeck coefficient than electrical conductivity over all temperature range.

• 한국세라믹학회지
• /
• 제47권5호
• /
• pp.457-460
• /
• 2010

$SmCoO_3$ system was investigated for their application to themoelectric materials. All specimens showed p-type semiconducting behavior and their electrical conductivity ($\sigma$), Seebeck coefficient (S) and power factor were measured at high temperature. And the effect of dopant ions on their thermoelectrical properties were also investigated. $Fe^{3+}$ ion doped into $Co^{3+}$ site enhanced the Seebeck coefficient and decreased the electrical conductivity simultaneously. The maximum Seebeck coefficient value for 60% doping case reached to 780 ${\mu}V$/K at $240^{\circ}C$. However $Fe^{3+}$ doped system cause an negative effect on power factor value. In case of the pure phase, the maximum Seebeck coefficient value reached to 290 ${\mu}V$/K at $240^{\circ}C$ and the maximum electrical conductivity was obtained 748 1/(ohm$\times$cm) at $960^{\circ}C$. As a result, the maximum power factor was obtained $1.49\times10^{-4}$ W/$mK^2$ at $550^{\circ}C$.

• 전기화학회지
• /
• 제23권1호
• /
• pp.18-23
• /
• 2020

Antimony telluride (Sb_xTe_y) thin films were synthesized by an electrodeposition method with a control of applied potential at room temperature. Characterization of electrical and thermoelectric properties such as conductivity, Seebeck coefficient, and power factor (P.F.) were conducted as a function of the chemical composition of the electrodeposited films. Morphology of thin films were dense and uniform and the composition was tailored from 25 to 60 at.% of the Sb content by altering the applied potential from -0.13 to -0.27 V (vs. SCE). The conductivity of the films were ranged from 2 × 10^-4 ~ 5 × 10^-1 S/cm indicating their amorphous behavior. The meaured Seebeck coefficient of films were relatively high compared to that of bulk single cyrstal Sb_xTe_y due to their low carrier concentration. The variation of the Seebeck coefficient of the films was also related to the change of chemical composition, showing the power factor of ~10 ㎼/mK².

• 한국세라믹학회지
• /
• 제56권3호
• /
• pp.325-330
• /
• 2019

Band convergence is known to be effective in improving thermoelectric performance by increasing the Seebeck coefficient without significantly reducing electrical conductivity. Decoupling of the Seebeck coefficient and electrical conductivity in converged bands is the key requirement. Yet, the degree of decoupling depends on the band parameters of the converging bands. Herein, we report theoretical transport properties of two valence bands as their energy difference changes from 0.25 eV to 0 eV. In order to demonstrate the effect of band parameters in transport, we first conducted calculations for the case where the two bands have the same parameters. Then, we conducted the same calculation by doubling the density-of-states effective mass of one valence band. Given that there are two bands, each band's effective mass was doubled one at a time while the other band's effective mass remained constant. We found that the decoupling was strongest when the bands participating in convergence had the same band parameters.

• 한국산학기술학회논문지
• /
• 제16권7호
• /
• pp.4835-4841
• /
• 2015

n형 FeSi2의 열전물성에 미치는 입자크기 및 성형압력의 영향에 대해 조사하였다. 입자크기가 다른 출발 분말을 각각 가압성형(성형압력; $70{\sim}220kg/cm^2$) 하였고, 제작한 성형체를 Ar 분위기 1473 K에서 7시간 소결한 후, 반도체상인 ${\beta}$상을 얻기 위해 1103 K에서 100시간 소둔처리 하였다. XRD, SEM 및 EDS를 이용해서 시편들의 미세구조 및 상분석을 행하였다. 동일 시료를 가지고 Ar 분위기 상온~1023 K에서 도전율과 Seebeck 계수를 동시에 측정하였다. 입자크기가 작을수록 소결밀도와 잔존 ${\varepsilon}$-FeSi 금속전도상 증가에 의해 도전율이 상승하였으며, Seebeck 계수는 700~800 K에서 최고값을 나타내었고, 입자크기가 작을수록 잔존 ${\varepsilon}$-FeSi 금속전도상 증가에 의해 감소하였다. 반면에 성형압력의 변화는 도전율 및 Seebeck 계수에 그다지 큰 영향을 미치지 않았다. 결과적으로 power factor는 성형압력 보다 입자크기에 큰 영향을 받았다.

• 한국재료학회지
• /
• 제13권8호
• /
• pp.543-549
• /
• 2003

In order to investigate the thermoelectric properties of $Zn_{k}$ $In_2$$O_{ 3＋k}$ homologous compounds, the samples of $Zn_{k}$ /$In_2$$O_{3＋k}$ / (k = integer between 1 and 9) were prepared by calcining the mixed powders of ZnO and $In_2$$O_3$fellowed by sintering at 1823 K for 2 hours in air, and their electrical conductivities and Seebeck coefficients were measured as a function of temperature in the range of 500 K to 1150 K. X-ray diffraction analysis of the sintered samples clarified that single-phase specimens were obtained for $Zn_{k} /$In_2$$O_{3＋k}$ with k = 3, 4, 5, 7, 8, 9. Electrical conductivity of the $Zn_{k}$ $In_2$$O_{3＋k}$ / decreased with increasing temperature, and decreased with increasing k for k $\geq$ 3. The Seebeck coefficient was negative at all the temperatures for all compositions, confirming that $Zn_{k}$ $In_2$$O_{3＋k}$ / is an n-type semiconductor. Absolute values of the Seebeck coefficient increased linearly with increasing temperature and increased with increasing k for k $\geq$ 3. The temperature dependence of the Seebeck coefficient indicated that Z $n_{k}$I $n_2$ $O_{3＋k}$ could be treated as an extrinsic degenerate semiconductor. Figure-of-merits of Z $n_{k}$I $n_2$ $O_{3＋k}$ were evaluated from the measured electrical conductivity and Seebeck coefficient, and the reported thermal conductivity. Z $n_{7}$ I $n_2$ $O_{10}$ has the largest figure-of-merit over all the temperatures, and its highest value was $1.5{\times}$10$^{-4}$ $K^{-1}$ at 1145 K.5 K.

• 한국결정성장학회지
• /
• 제15권2호
• /
• pp.75-78
• /
• 2005

본 연구에서는 고온 융점과 높은 Seebeck 계수로 인해 고온 열전 재료로서 매우 우수한 silicon boride ($SiB_6$)의 고밀도 소결체를 방전 플라즈마 소결법(spark plasma sintering, SPS)을 도입하여 제조하였으며, 소결된 시편의 미세구조 및 열전 특성을 평가하였다. $1500^{\circ}C$의 비교적 저온에서 이론 밀도의 약 99%의 소결밀도로 SPS법을 통해 효과적으로 $SiB_6$를 치밀화 할 수 있었으며 이들 시편들의 열전특성 평가로부터, hot-press법으로 제조된 시편과 비교하여 매우 향상된 Seebeck 계수를 얻을 수 있었으며 상대적으로 높은 출력인자 값을 나타냈다.