本研究探討CuO-doped TiO2的活化燒結緻密機制與其在束縛燒結下緻密行為。TiO2參雜少量CuO 可將燒結緻密溫度從1200oC降到900oC，透過相圖和熱分析驗證CuO-doped TiO2系統在900oC燒結過程中沒有生成液相協助燒結，CuO在燒結時則是以氣體的形式移動，並在晶界形成一富含Cu的晶界複合物(grain boundary complexions)結構。1 mol% CuO-doped TiO2 (TC1)系統於束縛燒結下燒結溫度約高於自由燒結100oC，並觀察到等向性的顯微結構，而由Z軸向施加壓應力提升束縛燒結下TC1的緻密度，在750-950oC使束縛燒結下的TC1具有與自由燒結相同的緻密速率所需之單軸向應力為200-1100 kPa，此結果與利用構成方程式(constitutive equations)的理論計算相符。此一可以在束縛燒結下燒結緻密的多晶陶瓷材料CuO-doped TiO2，其活化燒結機制是因為添加CuO後形成的晶界複合物具有較低之晶界能，而提高燒結驅動力，同時降低晶界移動活化能，因此提高晶界擴散能力，以此結果推測可在束縛燒結下緻密的多晶陶瓷系統可能與活化燒結的晶界複合物結構有關。

The effects of CuO on the sintering driving force and the grain growth kinetics of TiO2 have been investigated. The sintering temperature, 900oC, is below the eutectic point of CuO-TiO2 system. The Cu-rich grain boundary complexions are formed during sintering. Poorer densification is observed for the 1 mol% CuO-doped TiO2 densified under pressure-less constrained sintering in comparison to free sintering. No significant anisotropy is developed under free and constrained sintering. The applied uniaxial stress required in the thickness direction to densify 1 mol% CuO-doped TiO2 under constrained sintering at 750-950oC varies in the range of 200-1100 kPa, consistent with those calculated theoretically. By measuring dihedral angles, the Cu-rich grain boundary complexions have lower grain boundary energy to enhance driving force of sintering than pure TiO2 grain boundaries. The grain growth results show high grain boundary mobility and lower activation energy in CuO-doped TiO2 system. With grain boundary complexions existing, the polycrystalline CuO-doped TiO2 system can be densified under constrained sintering.

1. M. R. Gongora Rubio, P. Espinoza Vallejos, L. Sola Laguna, and J. Santiago Aviles, "Overview of Low Temperature Co-Fired Ceramics Tape Technology for Meso-System Technology (MsST)," Sens. Actuators, A: Phys., 89[3] 222-41 (2001).
2. F. Lautzenhiser and E. Amaya, "Self-Constrained LTCC Tape," Am. Ceram. Soc. Bull., 81[10] 27-32 (2002).
3. K. Mikeska and R. Jensen, "Pressure-Assisted Sintering of Multilayer Packages," Ceram. Trans., 15 629-50 (1989).
4. W. A. Vitriol and R. L. Brown, "Process for Fabricating Dimensionally Stable Interconnect Boards," US patent No. 4,656,552, 1987.
5. T. J. Garino and H. K. Bowen, "Kinetics of Constrained‐Film Sintering," J Am Ceram Soc, 73[2] 251-57 (1990).
6. B. Geller, B. Thaler, A. Fathy, M. Liberatore, H. Chen, G. Ayers, V. Pendrick, and Y. Narayan, "LTCC-M: an Enabling Technology for High Performance Multilayer RF Systems," J. Microwave, 42[7] 64-72 (1999).
7. K. R. Mikeska and D. T. Schaefer, "Method for Reducing Shrinkage During Firing of Ceramic Bodies," US patent 5,454,741, 1994.
8. J. C. Chang and J. H. Jean, "Self‐Constrained Sintering of Mixed Low‐Temperature‐Cofired Ceramic Laminates," J Am Ceram Soc, 89[3] 829-35 (2006).
9. J. J. Bian, D. W. Kim, and K. S. Hong, "Glass-Free LTCC Microwave Dielectric Ceramics," Mater. Res. Bull., 40[12] 2120-29 (2005).
10. D. K. Kwon, M. T. Lanagan, and T. R. Shrout, "Microwave Dielectric Properties of BaO–TeO2 Binary Compounds," Mater. Lett., 61[8] 1827-31 (2007).
11. D. J. Green, O. Guillon, and J. Rödel, "Constrained Sintering: A Delicate Balance of Scales," J. Eur. Ceram. Soc., 28[7] 1451-66 (2008).
12. R. T. Hsu, J. H. Jean, and Y. Y. Hung, "Stress Required to Densify a Low‐Fire NiCuZn Ferrite Under Constrained Sintering," J Am Ceram Soc, 91[6] 2051-54 (2008).
13. X. Wang and A. Atkinson, "Microstructure Evolution in Thin Zirconia Films: Experimental Observation and Modelling," Acta Mater., 59[6] 2514-25 (2011).
14. Y. L. Tung, T. M. Peng, J. H. Jean, and S. C. Lin, "Stress Development During the Co‐firing of Integrated Ferrite/Dielectric Laminates," J Am Ceram Soc, 95[3] 946-50 (2012).
15. L. Amaral, C. Jamin, A. M. Senos, P. M. Vilarinho, and O. Guillon, "Constrained Sintering of BaLa4Ti4O15 Thick Films: Pore and Grain Anisotropy," J. Eur. Ceram. Soc., 33[10] 1801-08 (2013).
16. R. K. Bordia and R. Raj, "Sintering Behavior of Ceramic Films Constrained by a Rigid Substrate," J Am Ceram Soc, 68[6] 287-92 (1985).
17. J. Choe, J. N. Calat, and G. Q. Lu, "Constrained-Film Sintering of a Gold Circuit Paste," J. Mater. Res., 10[04] 986-94 (1995).
18. R. Bordia and G. Scherer, "Sintering of Composites: A Critique of the Available Analyses," Ceramic Powder Science II. Transactions Westerville, Oh., 1988, 1 872-86 (1988).
19. R. K. Bordia and G. W. Scherer, "On Constrained Sintering—I. Constitutive Model for a Sintering Body," Acta Metall., 36[9] 2393-97 (1988).
20. R. K. Bordia and G. W. Scherer, "On Constrained Sintering—II. Comparison of Constitutive Models," Acta Metall., 36[9] 2399-409 (1988).
21. R. K. Bordia and G. W. Scherer, "On Constrained Sintering—III. Rigid Inclusions," Acta Metall., 36[9] 2411-16 (1988).
22. H. Hayden and J. Brophy, "The Activated Sintering of Tungsten with Group VIII Elements," J. Electrochem. Soc., 110[7] 805-10 (1963).
23. V. K. Gupta, D. H. Yoon, H. M. Meyer, and J. Luo, "Thin Intergranular Films and Solid-State Activated Sintering in Nickel-Doped Tungsten," Acta Mater., 55[9] 3131-42 (2007).
24. K. Hwang and H. Huang, "Identification of the Segregation Layer and its Effects on the Activated Sintering and Ductility of Ni-Doped Molybdenum," Acta Mater., 51[13] 3915-26 (2003).
25. J. Luo, H. Wang, and Y. M. Chiang, "Origin of Solid‐State Activated Sintering in Bi2O3‐Doped ZnO," J Am Ceram Soc, 82[4] 916-20 (1999).
26. H. Wang and Y. M. Chiang, "Thermodynamic Stability of Intergranular Amorphous Films in Bismuth‐Doped Zinc Oxide," J Am Ceram Soc, 81[1] 89-96 (1998).
27. T. Zhang, P. Hing, H. Huang, and J. Kilner, "Sintering and Grain Growth of CoO-doped CeO2 Ceramics," J. Eur. Ceram. Soc., 22[1] 27-34 (2002).
28. E. Jud, Z. Zhang, W. Sigle, and L. J. Gauckler, "Microstructure of Cobalt Oxide Doped Sintered Ceria Solid Solutions," J. Electroceram., 16[3] 191-97 (2006).
29. W. Kingery and M. Narasimhan, "Densification During Sintering in the Presence of a Liquid Phase. II. Experimental," J. Appl. Phys., 30[3] 307-10 (1959).
30. W. D. Kingery, "Densification During Sintering in the Presence of a Liquid Phase. I. Theory," J. Appl. Phys., 30[3] 301-06 (1959).
31. J. H. Jean and T. Gupta, "Liquid-Phase Sintering in the Glass-Cordierite System: Particle Size Effect," J. Mater. Sci., 27[18] 4967-73 (1992).
32. J. W. Gibbs, "The Scientific Papers of J. Willard Gibbs," Vol. 1. Longmans, Green and Company, (1906).
33. S. J. Dillon, M. Tang, W. C. Carter, and M. P. Harmer, "Complexion: A New Concept for Kinetic Engineering in Materials Science," Acta Mater., 55[18] 6208-18 (2007).
34. P. R. Cantwell, M. Tang, S. J. Dillon, J. Luo, G. S. Rohrer, and M. P. Harmer, "Grain Boundary Complexions," Acta Mater., 62 1-48 (2014).
35. J. Luo, "Developing Interfacial Phase Diagrams for Applications in Activated Sintering and Beyond: Current Status and Future Directions," J Am Ceram Soc, 95[8] 2358-71 (2012).
36. J. Luo, "Liquid-Like Interface Complexion: From Activated Sintering to Grain Boundary Diagrams," Curr. Opin. Solid State Mater. Sci., 12[5] 81-88 (2008).
37. S. J. Dillon and M. P. Harmer, "Demystifying the Role of Sintering Additives with “Complexion”," J. Eur. Ceram. Soc., 28[7] 1485-93 (2008).
38. J. Buban, K. Matsunaga, J. Chen, N. Shibata, W. Ching, T. Yamamoto, and Y. Ikuhara, "Grain Boundary Strengthening in Alumina by Rare Earth Impurities," Science, 311[5758] 212-15 (2006).
39. S. J. Dillon, M. P. Harmer, and G. S. Rohrer, "The Relative Energies of Normally and Abnormally Growing Grain Boundaries in Alumina Displaying Different Complexions," J Am Ceram Soc, 93[6] 1796-802 (2010).
40. R. Akiva, A. Katsman, and W. D. Kaplan, "Anisotropic Grain Boundary Mobility in Undoped and Doped Alumina," J Am Ceram Soc, 97[5] 1610-18 (2014).
41. S. Y. Chung and S. J. L. Kang, "Intergranular Amorphous Films and Dislocations-Promoted Grain Growth in SrTiO3," Acta Mater., 51[8] 2345-54 (2003).
42. S. Y. Choi, D. Y. Yoon, and S. J. L. Kang, "Kinetic Formation and Thickening of Intergranular Amorphous Films at Grain Boundaries in Barium Titanate," Acta Mater., 52[12] 3721-26 (2004).
43. T. Zhang, L. Kong, X. Song, Z. Du, W. Xu, and S. Li, "Densification Behaviour and Sintering Mechanisms of Cu-or Co-Doped SnO2: A Comparative Study," Acta Mater., 62 81-88 (2014).
44. J. Luo and X. Shi, "Grain Boundary Disordering in Binary Alloys," Appl. Phys. Lett., 92[10] 101901 (2008).
45. M. Park and C. A. Schuh, "Accelerated Sintering in Phase-Separating Nanostructured Alloys," Nat. Commun., 6 (2015).
46. Y. J. Chu and J. H. Jean, "Constrained Sintering of a Low‐Fire, Polycrystalline Bi2(Zn1/3Nb2/3)2O7 Dielectric," J Am Ceram Soc, 98[4] 1080-86 (2015).
47. 陳翊昇, "TiO2添加CuO之活化燒結," 清華大學材料科學工程學系學位論文 1-51 (2009).
48. P. Z. Cai, G. L. Messing, and D. J. Green, "Determination of the Mechanical Response of Sintering Compacts by Cyclic Loading Dilatometry," J Am Ceram Soc, 80[2] 445-52 (1997).
49. W. W. Mullins, "Theory of Thermal Grooving," J. Appl. Phys., 28[3] 333-39 (1957).
50. F. H. Lu, F. X. Fang, and Y. S. Chen, "Eutectic Reaction Between Copper Oxide and Titanium Dioxide," J. Eur. Ceram. Soc., 21[8] 1093-99 (2001).
51. C. D. Lei and J. H. Jean, "Effect of Crystallization on the Stress Required for Constrained Sintering of CaO–B2O3–SiO2 Glass–Ceramics," J Am Ceram Soc, 88[3] 599-603 (2005).
52. C. C. Huang and J. H. Jean, "Stress Required for Constrained Sintering of a Ceramic‐Filled Glass Composite," J Am Ceram Soc, 87[8] 1454-58 (2004).
53. Y. M. Chiang, W. D. Kingery, and D. P. Birnie, "Physical Ceramics: Principles for Ceramic Science and Engineering." J. Wiley, (1997).
54. J. Powers and A. Glaeser, "Grain Boundary Migration in Ceramics," Interface Sci., 6[1-2] 23-39 (1998).
55. A. Afshar and A. Simchi, "Abnormal Grain Growth in Alumina Dispersion-Strengthened Copper Produced by an Internal Oxidation Process," Scripta Mater., 58[11] 966-69 (2008).