鑄造技術已有數千年的歷史，在鑄造之凝固過程中，溫度與濃度場的變化會影響材料的顯微結構，而微結構之控制更是改善其機械性質及物理特性的關鍵所在。一般鑄造過程是不易控制其凝固結構之形態，最多只能改變其晶粒大小，而方向性凝固方法可製造出沿特定方向之柱形枝狀晶的鑄件，也是單晶成長之基礎。
本文探討方向性凝固機構分別對錫鉛合金與鉍碲合金之影響，並個別對此兩種合金進行微結構的討論與分析。
實驗一以錫鉛合金（Sn-10 wt.%Pb）為測試材料，採三種不同熱環境的實驗模式，來探討這些實驗模式對於凝固微結構的影響，並與方向性凝固機台做比較。於凝固實驗研究中，以熱電偶量測鑄件軸向與徑向的溫度分佈，並觀察凝固後鑄件的巨觀與微觀結構。探討其枝狀晶之優選方向控制情形、鑄件晶粒尺寸及對晶體成長的束縛控制及對其溫度梯度、成長速率之間的影響。
實驗二以鉍碲合金為測試材料，本實驗將利用方向性凝固機台成長Bi2Te3（59.7 at.％Te~60.2 at.％Te），並與火花電漿燒結法（Spark Plasma Sintering, SPS）燒結之塊材進行比較。成長後的晶體，將以XRD、SEM、EDS和ICP來鑑定晶體結構的品質與材料的成份。在300 K至500 K之間進行Seebeck係數、電阻率和熱傳導係數隨溫度變化的量測；並觀察各樣品在室溫時的霍爾係數及載子濃度等電特性，討論Bi2Te3晶體熱電性質與溫度的關係。

Casting skill has been developed for several thousands years. In a casting process, the temperature and concentration fields will affect the microstructures of materials and this influence is the key point of improving their mechanical and physical properties. The morphology of solidification microstructure is difficult to control in a casting process, in which only the grain size can be easily changed. Directional solidification techniques can fabricate the casting of columnar structures growing along one direction and it is also the base of single-crystal growth..
In this study, experimental analysis of making Sn-Pb alloy and Bi2Te3 alloy by using directional solidification mechanism. The effect of applying the mechanism on the resulting microstructures and properties are investigated.
In the first kind of experiment, Sn-Pb alloy (Sn-10 wt.%Pb alloy) is used as the testing material and three experimental models of different thermal environments are designed to study their effects on the solidification microstructures, whose results are also compared with those of applying directional solidification mechanism. In this experimental study, thermal couples are used to measure the radial and axial temperature distributions of the casting. After the solidification, the macro and micro structures are observed. The effects of these three models on preferred growth direction of dendrite, grain size, the constraint of dendrite growth, temperature gradient, growth rate are also investigated.
In the second kind of experiment, Bi2Te3 alloy(59.7 at.％Te~60.2 at.％Te) is used as the testing material. In this work, the Bi2Te3 crystals were grown by directional solidification mechanism and compared with those fabricated by spark plasma sintering method. The crystalline and composition were examined by XRD, SEM, EDS and ICP. The temperature dependence of the Seebeck coefficient, resistivity and thermal conductivity of Bi2Te3 crystals were measured at temperature range from 300 K to 500 K. Hall effect measurement was carried out at room temperature. The temperature dependence of thermoelectric properties for these materials were discussed.

[1] William F. Smith原著；李春穎，許煙明，陳忠仁 譯，材料科學與工程，高立圖書，1994。
[2] Donald R. Askeland原著；陳黃鈞譯，材料科學與工程上冊，暁園出版社，1989。
[3] M. Rettenmayer, and H. E. Exner, “Directional Solidification,” Materials Science and Technology, pp. 2183-2189, 2001.
[4] C. M. Klaren, J. D. Verhoeven, and R. Trivedi, “Primary Dendrite Spacing of Lead Dendrites in Pb-Sn and Pb-Au Alloys,” Metallurgical Transactions 11A, pp. 1853-1861, 1980.
[5] D. G. McCartney, and J. D. Hunt, “Measurements of Cell and Primary Dendrite Arm Spacings in Directionally Solidified Aluminum Alloys,” Acta Metallurgica, Vol. 29, pp. 1851-1863, 1981.
[6] Guolu Ding, Weidong Huang, Xin Lin, and Yaohe Zhou “Predication of Average Spacing for Constrained Cellular/Dendrite Growth,” Journal of Crystal Growth 177, pp. 281-288, 1997.
[7] C. T. Rios, and R. Caram, “Primary Dendrite Spacing as a Function of Directional Solidification Parameters in an Al-Si-Cu Alloy,” Journal of Crystal Growth 174, pp. 65-69, 1997.
[8] Ming Li, Takassuke Mori, and Hajime Iwasaki, “Effect of Solute Convection on The Primary Arm Spacings of Pb-Sn Binary Alloys During Upward Directional Solidification,” Materials Science and Engineering A265, pp. 217-223, 1999.
[9] E. Cadirli, and M. Gunduz, “The Directional Solidification of Pb-Sn Alloys,” Journal of Materials Science 35, pp. 3837-3848, 2000.
[10] E. Cadirli, and M. Gunduz, “The Dependence of Lamellar Spacing on Growth Rate and Temperature Gradient in the lead-tin Eutectic Alloy,” Journal of Materials Processing Technology 97, pp. 74-81, 2000.
[11] Otavio Lima Rocha, Claudio Alves Siqueira, and Amauri Garcia, “Cellular/Dendritic Transition During Unsteady-State Unidirectional Solidification of Sn-Pb Alloys,” Materials Science and Engineering A347, pp. 59-69, 2003.
[12] Otavio Lima Rocha, Claudio Alves Siqueira, and Amauri Garcia, “Cellular Spacings in Unsteady-State Directionally Solidified Sn-Pb Alloys,” Materials Science and Engineering A361, pp. 111-118, 2003.
[13] Fernando sa, Otavio Lima Rocha, Claudio Alves Siqueira, and Amauri Garcia, “The Effect of Solidification Variables on Tertiary Dendrite Arm Spacing in Unsteady-State Directional Solidification of Sn-Pb and Al-Cu Alloys,” Materials Science Engineering A373, pp. 131-138, 2004.
[14] J. E. Spinelli, I. L. Ferreira, and A. Garcia, “Influence of Melt Convection on the Columnar to Equiaxed Transition and Microstructure of Downward Unsteady-State Directionally Solidified Sn-Pb Alloys,” Journal of Alloys and Compounds 384, pp. 217-226, 2004.
[15] H. B. Dong, and P. D. Lee, “Simulation of the Columnar-to-Equiaxed Transition in Directionally Solidified Al-Cu Alloys,” Acta Materialia, Vol. 53, No. 3, pp. 659-668, 2005.
[16] Terry M. Tritt, and M. A. Subramanian, “Thermoelectric Materials, Phenomena, and Applications: A Bird’s Eye View,” MRS Bulletin, Vol. 31, pp. 188-198, 2006.
[17] Brian Sales, “Progress in New Thermoelectric Materials,” Fall 2004 MRS Meeting, Boston MA Symposium S 4.5.
[18] Terry M. Tritt, and M. A. Subramanian, “Harvesting Energy through Thermoelectric: Power Generation and Cooling,” MRS Bulletin, Vol. 31, No. 3, 2006.
[19] 林曉洪，王秀華，“再生能源的明日之星—生質能”，臺灣林業期刊，Vol. 31，No. 3，2005。
[20] Francis J. DiSalvo, “Thermoelectric Cooling and Power Generation,” Science, Vol. 285, pp. 703-706, 1999.
[21] G. J. Cosgrove, J. P. McHugh, and W. A. Tiller, “Effect of Freezing Conditions on the Thermoelectric Properties of BiSbTe[sub 3] Crystals,” J. Appl. Phys., 32, 621, 1961.
[22] A. C. Yang, F. D. Shepherd, J. Electrochem. Soc., 108, 197, 1961.
[23] F. J. Strieter: Adv. Energy Convers., 1, 125, 1961.
[24] R. B. Horst, and L. R. Williams, “Proceedings, Fourth International Conference on Thermoelectric Energy Conversion,” Arlington, pp. 119, 1982.
[25] H. P. Ha, Y. W. Cho, J. Y. Byun, and J. D. Shim, “Proc. 12th Inter. Conf. on Thermoelectrics,” Yokohama, Japan, pp. 105, 1993.
[26] J. R. Joseph, and P. M., ”Synthesis of Polycrystalline Bismuth Telluride by a Metal-Organo Complex Method,” Inorg. Chem., 34, pp. 4278-4280, 1995.
[27] J. R. Joseph, Inorg. Chem., 36, pp. 260-263, 1997.
[28] R. Venkatasubramanian, T. Colpitts, E. Watko, M. Lamvik, and N. El-Masry, “MOCVD of Bi2Te3, Sb2Te3 and Their Superlattice Structures for Thin-Film Thermoelectric Application,” J. Cryst. Growth, 170, pp. 817-821, 1997.
[29] H. Kaibe, M. Sakata, Y. Isoda, and I. Nishida, J. Jpn. Inst. Met. 53, 958, 1989.
[30] D. B. Hyun, J. S. Hwang, J. D. Shim, and T. S. Oh, J. Mater. Sci. 36, 1285, 2001.
[31] J. Seo, C. Lee, and K. Park, J. Mater. Sci. 35, 1549, 2000.
[32] Xisong Zhou, Jun Nan, Junbo Wu, and Ce Wen Nan, 20th International Conference on Thermoelectrics, 2001.
[33] J. Yang, T. Aizawa, A. Yamamoto, and T. Ohta, Mater. Chem. Phys. 70, pp. 90-94, 2001.
[34] S. S. Kim, S. Yamamoto, and T. Aizawa, J. Alloys Compd. 375, pp. 107-113, 2004.
[35] Y. Iwaisoko, T. Aizawa, A. Yamamoto, and T. Ohta, Jpn. J. Powder Metal. 45, 958, 1998.
[36] J. Y. Yang, T. Aizawa, A. Yamamoto, and T. Ohta, J. Alloys Compd. 312, 326, 2000.
[37] D. M. Lee, C. H. Lim, D. C. Cho, Y. S. Lee, and C. H. Lee, “Effects of Annealing on the Thermoelectric and Microstructural Properties of Deformed n-type Bi2Te3-Based Compounds,” Journal of Electronic Materials, Vol. 35, No. 2, 2006.
[38] M. Yamaguchi, D. R. Johnson, H. N. Lee, and H. Inui, “Directional solidification of TiAl-base alloys,” Intermetallics, Vol. 8, No. 5-6, pp. 511-517, 2000.
[39] 何廣福，“方向性凝固之研究”，國立成功大學工程科學研究所碩士論文，2005。
[40] 趙國傑，“凝固參數對於方向性成長之結構參數影響分析”，國立成功大學工程科學研究所碩士論文，2007。
[41] 呂璞石，黃振賢，“金屬材料”，文京圖書，pp. 39，1990。
[42] 林盈佐，“凝固顯微組織與模式分析”，國立成功大學工程科學研究所碩士論文，1998。
[43] W. Kurz, and D. J. Fisher, “Fundamentals of Solidification,” Tran Tech Publication Ltd, Switzerland, 1998.
[44] William F. Smith 原著 ; 李春穎，許煙明，陳忠仁 譯，“材料科學與工程”，高立圖書有限公司，1994。
[45] Reed-Hill, Abbaschian 原著；劉偉隆，林淳杰，曾春風，陳文照 譯，“物理冶金”，全華科技圖書，1995。
[46] 林明獻，“矽晶圓半導體材料技術”，全華圖書股份有限公司，2007。
[47] T. J. Seebeck, “Magnetic Polarization of Metals and Minerals,” Abhandlungen der Deutschen Akademie der Wissenchaften zu Berlin, Vol. 265, pp. 1822-1823, 1823.
[48] J. C. Peltier, “Nouvelles experience sur la caloricite des courans electrique,” Ann.Chim., Vol. LV1, pp. 371, 1834.
[49] H. J. Goldsmid, “Electronic Refrigeration,” pp. 1-194, 1986.
[50] W. Thomson, “On a Mechanical Theory of Thermo-Electric Currents,” Proceeding of the Royal Society of Edinburgh, pp. 91-98, 1851.
[51] Gerald Mahan, Brian Sales, Jeff Sharp, Physics Today, March 1997, 42, 1997.
[52] N. Scoville, C. Bajgar, J. P. Fleurial, and J. Vandersande, “Thermal Conductivity Reduction in SiGe Alloys by the Addition of Nanophase Particles,” Nanostuctured Materials, Vol. 5, No. 2, pp. 207-223, 1995.
[53] D. M. Rowe., “Thermoelectrics Handbook：Macro to Nano,” Taylor & Francis, Boca Raton :CRC, 2006.
[54] Cronin B. Vining, “Thermoelectric Fundamentals and Physical Phenomena,” the 1993 ITS Short Course on Thermoelectricity No. 8, 1993.
[55] W. A. Tiller, and J. P. Mchung, Trans. Amer. Inst. Min. (Metall)Engrs., 215, 651, 1959.
[56] J. R. Drabble, and C. H. L. Goodman, J. Phy. Chem. Solids, 5, 142, 1958.
[57] H. J. Noh, H. Koh, S. J. Oh, J. H. Park, H. D. Kim, J. D. Rameau, T. Valla, T. E. Kidd, P. D. Johnson, Y. Hu, and Q. Li, “Spin-Orbit Interaction Effect in the Electronic Structure of Bi2Te3 Observed by Angle-Resolved Photoemission Spectroscopy,” EPL., Vol. 81, pp. 57006-p1, 2008.
[58] P. W. Lange, Naturwiss., Vol. 27, 133, 1939.
[59] C. B. Satterthwaite, and R. W. Ure, Jr., Phys. Rev.108, 1164, 1957.
[60] B. M. Thaddeus, “Binary Alloy Phase Diagrams,” ASM International, 1990.
[61] J. P. Fleurial, L. Gailliard, R. Triboulet, H. Scherrer, and S. Scherrer, “Thermal Properties of High Quality Single Crystals of Bismuth Telluride-Part I: Experimentalcharacterization,” Journal of Physics and Chemistry of Solids, Vol. 49, pp. 1237-1247, 1988.
[62] Brebrick, R. F., J. Phys. Chem. Solids, 30, 719, 1969.
[63] http://www.scm-sps.com/e_htm/whatsps_e_htm/whatsps_e.htm
[64] http://www.elecmat.com/
[65] 韋孟育，“材料實驗方法-金相分析技術”，全華科技圖書股份有限公司，pp. 14，1990。
[66] Otávio Lima Rocha, Cláudio Alves Siqueira, and Amauri Garcia, “Cellular/Dendritic Transition During Unsteady-State Unidirectional Solidification of Sn-Pb Alloys,” Materials Science and Engineering A, Vol. 347, No. 1-2, pp. 59-69, 2003.
[67] “Standard Methods for Estimationg the Average Grain Size of Metals” , Annual Books of ASTM Standards, Vol. 03, ASTM, USA, pp. 120-156, 1984.
[68] 島田賢次, “熱電特性評価装置「ZEM－３」の最新技術”, Ulvac Technical Journal, No. 65, 2006.
[69] V. L. Kuznetsov, L. A. Kuznetsova, and D. M. Rowe, J. Phys. D: Appl. Phys. 34, pp. 700-703, 2001.
[70] Joseph P. Heremans, Vladimir Jovovic, Eric S.Toberer, Ali Saramat, Ken Kurosaki, Anek Charoenphakdee, Shinsuke Yamanaka, and G.Jeffrey Snyder, “Enhancement of Thermoelectric Efficiency in PbTe by Distortion of the Electronic Density of States,” Vol. 321, pp. 554-557, 2008.
[71] J. Navratil, Z. Stary, and T. Plechaoek, Mater. Res. Bull. 31, pp. 1559-1566, 1996.
[72] 李雅明，“固態電子學”，91-121，pp.235-257，1997。