MA법에 의한 Mn-Si계 초미세 열전재료의 제조 및 평가

이충효,Lee, Chung-Hyo 한국결정성장학회 2011 韓國結晶成長學會誌 Vol.21 No.6

The semiconducting $MnSi_{1.73}$ compound has been recognized as a thermoelectric material with excellent oxidation resistance and stable characteristics at elevated temperature. In the present work, we applied mechanical alloying (MA) technique to produce $MnSi_{1.73}$ compound using a mixture of elemental manganese and silicon powders. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-$K{\alpha}$ radiation, thermal analysis and scanning electron microscopy. Due to the observed larger loss of Si relative to Mn during mechanical alloying of $MnSi_{1.73}$, the starting composition of a mixture Mn-Si was modified to $MnSi_{1.83}$ and then $MnSi_{1.88}$. The single $MnSi_{1.73}$ phase has been obtained by mechanical alloying of $MnSi_{1.88}$ mixture powders for 200 hours. It is also found that the grain size of $MnSi_{1.73}$ compound powders analyzed by Hall plot method is reduced to 40 nm after 200 hours of milling. 반도성 $MnSi_{1.73}$ 화합물은 고온 특성이 우수하고 뛰어난 내산화성을 가진 열전재료로서 알려져 있다. 본 연구에서는 순 Mn 및 Si 분말재료를 출발 원료로 기계적 합금화법(MA)을 적용하여 $MnSi_{1.73}$ 화합물 합성을 실시하였다. MA 처리는 P-5 유성형 볼밀장치를 이용하여 Ar 중에서 행하였다. MA 분말재료의 X선 회절, 열분석 및 전자현미경 분석을 통하여 고상반응을 관찰하였다. MA 공정 중 Si의 손실을 고려하여 화학양론 조성에서 Si 양을 증가시켜 $MnSi_{1.73}$ 화합물 합성을 시도하였다. 그 결과 $MnSi_{1.73}$ 화합물 단상은 $MnSi_{1.88}$ 조성의 혼합 분말을 200시간 볼밀 처리함으로써 얻을 수 있었다. 또한 200시간 볼밀 처리에 의하여 제조된 $MnSi_{1.73}$ 화합물의 평균결정립 크기는 40 nm 임을 X 선 회절피크의 Hall plot으로 부터 알 수 있었다.

Synthesis and Comparative Analysis of Crystallite Size and Lattice Strain of Pb2Ba1.7Sr0.3Ca2Cu3O10+ Superconductor

Maher Abd Ali Hasan,Kareem Ali Jasim,Hussein Ali Jan Miran 한국재료학회 2022 한국재료학회지 Vol.32 No.2

In this article, Pb2Ba1.7Sr0.3Ca2Cu3O10+δ superconductor material was synthesized using conventional solid-state reaction method. X-ray diffraction (XRD) analysis demonstrated one dominant phase 2223 and some impurities in the product powder. The strongest peaks in the XRD pattern were successfully indexed assuming a pseudo-tetragonal cell with lattice constants of a = 3.732, b = 3.733 and c = 14.75 Å for a Pb-Based compound. The crystallite size and lattice strain between the layers of the studied compound were estimated using several methods, namely the Scherrer, Williamson-Hall (W.H), sizestrain plot (SSP) and Halder Wagner (H.W) approach. The values of crystallite size, calculated by Scherrer, W.H, SSP and H.W methods, were 89.4540774, 86.658638, 87.7555823 and 85.470086 Å, respectively. Moreover, the lattice strain values obtained by W.H, SSP and H.W methods were 0.0063240, 0.006325 and 0.006, respectively. It was noted that all crystallite size results are consistent; however, the best method is the size-strain plot because it gave a value of R2 approaching one. Furthermore, degree of crystallites was calculated and found to be 59.003321%. Resistivity analysis suggests zero-resistance, which is typical of superconducting materials at critical temperature. Four-probe technique was utilized to measure the critical temperature at onset Tc(onset), zero resistivity Tc(off set), and transition (width ΔT), corresponding to temperatures of 128 K, 116 K, and 12 K, respectively.

Dependence of Annealing Temperature on Properties of PZT Thin Film Deposited onto SGGG Substrate

임인호,정광현,김덕현 한국전기전자재료학회 2014 Transactions on Electrical and Electronic Material Vol.15 No.5

Pb(Zr0.52Ti0.48)O3 thin films of 1.5 μm thickness were grown on Pt/Ti/Gd3Ga5O12 substrate by RF magnetron sputteringat annealing temperatures ranging from 550℃ to 700℃. We evaluated the residual stress, by using a William-Hall plot,as a function of the annealing temperatures of PZT thin film with a constant thickness. As a result, the residual stressesof PZT thin film of 1.5 μm thickness were changed by varying the annealing temperature. Also, we measured thehysteresis characteristic of PZT thin films of 1.5 μm thickness to evaluate for application of an optoelectronic device.

Effect of mesopore-induced strain/stress on the thermoelectric properties of mesoporous ZnO thin films

Hong, Min-Hee,Shim, Dong Il,Cho, Hyung Hee,Park, Hyung-Ho Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.446 No.-

<P><B>Abstract</B></P> <P>In present study, induced strain and stress effect of mesoporous structure on the thermoelectric properties of ZnO thin films were systematically investigated. In this work, mesoporous ZnO thin films were synthesized by evaporation-induced self-assembly and sol-gel process. As the pore structure is formed, the grain growth of ZnO is inhibited and lattice distortion is induced. In this paper, strain/stress induction according to surfactant (Brij-S10) concentration was analyzed through Williamson-Hall analysis. And the relationship between strain induction and thermoelectric properties was studied. 0.07 M ratio of Brij-S10 to Zn induces the enhanced thermoelectric properties as compared with pristine ZnO thin films. Hence, the induced strain and stress could play an important role in enhancing the thermoelectric properties of mesoporous ZnO thin films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of mesoporous ZnO thin films using evaporation-induced self-assembly process. </LI> <LI> XRD peak was broadened as increased surfactant concentration. </LI> <LI> Induced strain, stress, and energy density was calculated by using Williamson-Hall analysis. </LI> <LI> Improved thermoelectric property followed by mesoporous structure and tensile strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation on the Structural, Optical, and Vibrational Properties of Lead-Free (1 − x) Na0.5Bi0.5TiO3-xBiMnO3 Ceramics

Muniyandi Muneeswaran,김동훈,정번성,정중현,장재원,최병천 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.3

Single-phased [(1 − x) NBT-xBMO, x = 0.01 (NBTBM1), (1 − x) NBT-xBMO, x = 0.02 (NBTBM2), (1 − x) NBT-xBMO, x = 0.03 (NBTBM3), and (1 − x) NBT-xBMO, x = 0.04 (NBTBM4)] ceramic samples were prepared by using a solid-state method. X-ray diffraction analysis of the (1 − x) NBT-xBMO sample showed a rhombohedral structure and space group of R3c symmetry and confirmed the Rietveld refinement of the X-ray diffraction data. The micro-strain and the crystal sizes were calculated by using Williamson-Hall plots and experimentally verified with microstructural analyses. The in band-gap energy Eg varied from 3.28 to 3.17 eV for the (1 − x) NBT-xBMO ceramic samples. Furthermore, Raman spectra measured in the range from 100 to 1000 nm for the NBT-BMO powder samples showed new phonon modes and shifts to lower frequencies, which may be attributed to the incorporation of BMO into the NBT lattice.

Dependence of Annealing Temperature on Properties of PZT Thin Film Deposited onto SGGG Substrate

Im, In-Ho,Chung, Kwang-Hyun,Kim, Duk-Hyun The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.5

$Pb(Zr_{0.52}Ti_{0.48})O_3$ thin films of $1.5{\mu}m$ thickness were grown on $Pt/Ti/Gd_3Ga_5O_{12}$ substrate by RF magnetron sputtering at annealing temperatures ranging from $550^{\circ}C$ to $700^{\circ}C$. We evaluated the residual stress, by using a William-Hall plot, as a function of the annealing temperatures of PZT thin film with a constant thickness. As a result, the residual stresses of PZT thin film of $1.5{\mu}m$ thickness were changed by varying the annealing temperature. Also, we measured the hysteresis characteristic of PZT thin films of $1.5{\mu}m$ thickness to evaluate for application of an optoelectronic device.

Effects of Cu+ ion implantation on band gap and Raman shift of Cu2ZnSnS4 thin films

Kim Chan,Hong Sungwook 한국물리학회 2023 Current Applied Physics Vol.50 No.-

In this study, shifts in the band gap and position of the main Raman peak of Cu2ZnSnS4 (CZTS) thin films were analyzed. These shifts were caused by residual tensile strain originating from artificially implanted Cu+ ions on the CZTS thin films. Cu+ ions were implanted at various doses in the CZTS thin films. The residual strain increased linearly as the logarithmic dose of Cu+ ions increased. According to the Raman spectrum analysis, the CZTS thin films had kesterite order structures. The band gap and the shift of the main Raman peak, P1, are linear functions of the residual strain and are linearly related to each other. A larger residual strain led to larger decreases of 1.50 eV and 337.5 cm-1 in the band gap and position of the main Raman peak (P1), respectively.

MA법에 의한 Heusler Fe₂VAl 합금분말의 제조 및 치밀화

김광덕,이충효,Kim, Kwang-Duk,Lee, Chung-Hyo 한국결정성장학회 2013 韓國結晶成長學會誌 Vol.23 No.1

본 연구에서는 Heusler $Fe_2VAl$ 열전화합물을 제조하기 위하여 순금속 $Fe_{50}V_{25}Al_{25}$ 혼합분말을 기계적 합금화 처리하였다. $Fe_2VAl$ 열전화합물을 얻기 위하여 최적 볼밀조건 및 열처리 조건을 X선 회절분석과 시차주사 열량분석을 이용하여 조사하였다. $Fe_{50}V_{25}Al_{25}$ 혼합분말을 60시간까지 볼밀 처리한 경우 bcc 구조의 ${\alpha}$-(Fe,V,Al) 고용체가 얻어졌다. 단상의 Heusler $Fe_2VAl$ 화합물은 $Fe_{50}V_{25}Al_{25}$ 혼합분말을 60시간 동안 MA 처리 후 $700^{\circ}C$까지 열처리함으로써 얻을 수 있었다. MA 분말시료의 치밀화를 위하여 인가압력 60 MPa 및 소결온도 $900{\sim}1000^{\circ}C$에서 흑연다이를 사용하여 SPS 소결을 실시하였다. $1000^{\circ}C$에서 SPS 소결 후 얻어진 벌크체의 Vickers 경도는 870으로 매우 높은 값을 보였다. 또한 SPS 법으로 얻어진 벌크체의 밀도측정 결과, 모든 시료에서 상대밀도 90 % 이상의 금속광택을 나타내는 치밀한 소결체임을 알 수 있었다. We have applied mechanical alloying (MA) to produce Heusler $Fe_2VAl$ thermoelectric alloy using a mixture of elemental $Fe_{50}V_{25}Al_{25}$ powders. An optimal milling and heat treatment conditions to obtain the single phase of Fe2VAl compound with fine microstructure were investigated by X-ray diffraction and differential scanning calorimetry (DSC) measurement. The $Fe_{50}V_{25}Al_{25}$ MA sample ball-milled for 60 hours exhibits a bcc ${\alpha}$-(Fe,V,Al) solid solution. Single phase of Heusler $Fe_2VAl$ compound can be obtained by MA of $Fe_{50}V_{25}Al_{25}$ mixture for 60 hours and subsequently heated up to $700^{\circ}C$. Sintering of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies at $900{\sim}1000^{\circ}C$ under 60 MPa. The Vickers hardness of bulk sample sintered at $1000^{\circ}C$ was high value of Hv 870. All compact bodies have a high relative density above 90 % with metallic glare on the surface.

Formation of nanocrystalline MoSi₂compound subjected to mechanical alloying

Chung-Hyo Lee 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3

Molybdenum disilicide has been recognized as an attractive candidate material for high temperature structural applications. In this study, we have used mechanical alloying by a high-energy ball milling process to produce alloy powders of α-MoSi2 starting from mixtures of elemental molybdenum and silicon powders at room temperature. The α-MoSi2 plus Mo phases have been obtained by ball milling of a Mo33Si67 mixture of the pure elements for 100 hours, which was transformed to a single α-MoSi2 phase by subsequent heat treatment up to 725 oC. The grain size of the α-MoSi2 powders thus obtained was 19 nm, being approximately four times smaller than that of commercial alloy powders. It was also seen that the α-MoSi2 phase once formed begins to transform to the high-temperature β-MoSi2 phase when the total milling time exceeds 160 hours. Molybdenum disilicide has been recognized as an attractive candidate material for high temperature structural applications. In this study, we have used mechanical alloying by a high-energy ball milling process to produce alloy powders of α-MoSi2 starting from mixtures of elemental molybdenum and silicon powders at room temperature. The α-MoSi2 plus Mo phases have been obtained by ball milling of a Mo33Si67 mixture of the pure elements for 100 hours, which was transformed to a single α-MoSi2 phase by subsequent heat treatment up to 725 oC. The grain size of the α-MoSi2 powders thus obtained was 19 nm, being approximately four times smaller than that of commercial alloy powders. It was also seen that the α-MoSi2 phase once formed begins to transform to the high-temperature β-MoSi2 phase when the total milling time exceeds 160 hours.

열간 압연용 워크 롤로 사용되는 1.6 wt% C 고탄소강의 동적 재결정 거동 및 미세조직 변화

안유정(Y. J. An),전재열(J. Y. Jeon) 한국소성·가공학회 2023 한국소성가공학회 학술대회 논문집 Vol.2023 No.11