在本研究中，利用傳統之固態反應法，添加氧化譜(Pr6O11)及氧化鈷(Co3O4)於氧化鋅(ZnO)變阻器中。為了降低燒結溫度，則以添加微量之碳酸鈉(Na2CO3)燒結助劑幫助燒結。本研究主要探討燒結助劑，燒結溫度，冷卻方式對Pr6O11-ZnO陶瓷體變阻特性之影響。研究中以X光繞射儀(XRD)鑑定以及計算PrOx之結晶相之量、以場發射電子顯微鏡(FESEM)觀察胚體之顯微組織、以電子微探儀(EPMA)了解Pr以及Na之分佈，以了解這些因素對ZnO變阻器變阻特性之影響。
實驗結果顯示，當胚體中PrOx結晶量較多時，變阻特性較佳。添加微量的Na2CO3有助於變阻特性之提升。當冷卻速率較慢時，由於可增加氧在晶界上擴散的時間，有助於Pr及Co以高價存在，由於過渡金屬Co若在高價態取代Zn之位置，將產生鋅空缺，而有助於氧之化學吸附，形成界面陷阱，而提升變阻特性；而在冷卻速率越快時，PrOx則會富集在triple point，導致變阻特性變差。
整體而言，製程條件為添加Na2CO3、燒結溫度：1200oC、冷卻速率：2oC/min的樣品具有最佳的變阻特性，其α值為19.6；Eb值為637.6V/mm，IL為285μA。

In this study, ZnO varistor doped with Pr6O11, Co3O4, were prepared using traditional solid-state reaction method. In order to decrease the sintering temperature, trace additive, Na2CO3, was added as a sintering aid. The effects of the additive, sintering temperatures, cooling rate on the microstructures and electrical properties of (Pr,Co,Na)-added ZnO ceramics were investigated using XRD, XPS, FESEM, and EPMA.
The observed results can be described as follows:
1. The samples added Na2CO3 possessed better varistor properties.
2. Better varistor properties can be obtained for the samples with much crystalline PrOx phase.
3. For the sample with a slow cooling rate, O2 had a much time to diffuse at grain boundary which resulted in the more adsorption of O2 on the surfaces of the grains. Therefore the superior varistor properties were obtained for the sample with a slow cooling rate compared to the sample with a rapid cooling rate. For the sample with a rapid cooling rate, PrOx phase was observed to be rich in triple point, which resulted in the degradation of varistor properties.
In conclusion, the Pr-doped ZnO ceramics added with Na2CO3, sintered at 1200oC, and at cooling rate of 2oC/min can obtain the best varistor properties: α is 19.6 , Eb is 637.6 V/mm, and IL is 285μA.

1. 高志鈞，「氧化鋅變阻器的製作與應用」，材料與社會43 (1990) 47-55 .
2. 國立編譯館、邱碧秀，「電子陶瓷材料」，徐氏基金會出版。(1988) 197-239.
3. A. J. Moulson, and J. M. Herbert, “Electroceramics Materials‧Properties‧Applications”, London , Chapman and Hall ,New York (1990) p131.
4. K. Mukae, K. Tsuda, and I. Nagasawa, “Non-Ohmic Properties of ZnO-Rare Earth Metal Oxide-Co3O4 Ceramics”, Jpn. J. Appl. Phys. 16 (1977) 1361-1368.
5. K. Mukae, “Zinc Oxide Varistors with Praseodymium Oxide”, Ceram. Bull. 66 (1987)1329-1331.
6. A. B. Alles, and V. L. Burdick “The Effect of Liquid-Phase Sintering of Pr6O11-Based ZnO Varistors”, J. Appl. Phys. 70 (1991) 6883-6890.
7. A. B. Alles, R. Puskas, G. Callahan, and V. Burdick, “Compositional Effects on the Liquid-Phase Sintering of Praseodymium Oxide-Based Zinc Oxide Varistors” J. Am. Ceram. Soc. 76 (1993) 2098-2102.
8. Y. S. Lee, K. S. Liao, and T. Y. Tseng “Microstructure and Crystal Phases of Praseodymium Oxides in Zinc Oxide Varistor Ceramics”, J. Am. Ceram. Soc. 79 (1996) 2379-2384.
9. S. Y. Chun, N. Wakiya, h. Funakubo, K. Shinozaki, and N. Mizuyani, “Phase Diagram and Microstructure in the ZnO-Pr2O3 System”, J. Am. Ceram. Soc 80 (1997) 995-998
10. N. Wakiya, S. Y. Chun, K. Shinozaki, and N. Mizutani “Redox Reaction of Praseodymium Oxide in the ZnO Sintered Ceramics”, J. Solid State Chemistry 149 (2000) 349-353.
11. N. Wakiya, S. Y. Chun, C. H. Lee, O. Sakurai, K. Shinozaki, and N. Mizutani, “Effect of Liquid Phase and Vaporization on the Formation of Microstructure of Pr Doped ZnO Varistor”, J. Elect. Ceram, 4 (1999) 15-23.
12. C. W. Nahm, and H. S. Kim, “Effect of Pr6O11/CoO Mole Ratio on Nonlinear Properties and DC Accelerated Aging Characteristics of ZnO-Pr6O11-CoO-Dy2O3-Based Varistors”, Mater. Lett. 56 (2002) 379-385.
13. C. W. Nahm, “Influence of Praseodyium Oxide/Cobalt Oxide Ratio on Microstructure and Electrical of Zinc Oxide Varistor Ceramics”, Mater. Chem. Phys. 80(2003) 746-751.
14. C. W. Nahm, B. C. Shin, and B. H. Min, “Microstructure and Electrical Properties of Y2O3-doped ZnO-Pr6O11-Based Varistor Ceramics”, Mater. Chem. Phys. 82 (2003) 157-164.
15. C. W. Nahm, and B. C. Shin, “Effect of Sintering Time on Electrical Properties and Stability Against DC Accelerated Aging of Y2O3-doped ZnO-Pr6O11-Based Varistor Ceramics”, Ceramics International 30 (2004) 9-15.
16. C. W. Nahm, “The Electrical Properties and DC Degration Characteristics of Dy2O3 doped Pr6O11-Based ZnO Varistors”, J. Europ. Ceram. Soc. 21 (2001) 545-553.
17. C. W. Nahm, “Nonlinear Electrical Properties and DC Accelerated Aging Characteristics of ZnO-Pr6O11-CoO-Cr2O3-Dy2O3-based Varistors’’, Solid State Communications 127 (2003) 389-393.
18. C. W. Nahm, “Microstructure and Electrical Properties of Dy2O3-Doped ZnO-Pr6O11-Based Varistor Ceramics”, Mater. Lett. 58 (2004) 2252-2255.
19. C. W. Nahm, J. A. Park, B. C. Shin, and I. S. Kim, “Electrical Properties and DC-Accelerated Aging Behavior of ZnO-Pr6O11-CoO-Cr2O3-Dy2O3-Based Varistor Ceramics”, ceramics international 30 (2004) 1009-1016.
20. C. W. Nahm, and C. H. Park, “Effect of Er2O3 Addition on the Microstructure, Electrical Properties, and Stability of Pr6O11-Based ZnO Ceramic Varistors”, J. Mater. Sci. 36 (2001) 1671-1679.
21. C. W. Nahm, and J. S. Ryu, “Influence of Sintering Temperature on Varistor Characteristics of ZPCCE-Based Ceramics”, Mater. Lett. 53 (2002) 110-116.
22. C. W. Nahm, “Nonlinear Properties and Stability Against DC Accelerated Aging Stress of Praseodyium Oxide-Based ZnO Varistors by Er2O3 Doping”, Solid State Communications 126 (2003) 281-284.
23. C. W. Nahm, “Electrical Properties and Stability of Praseodyium Oxide-Based ZnO Varistor Ceramics Doped with Er2O3”, J. Europ. Ceram. Soc. 23 (2003) 1345-1353
24. T. K. Gupta, “Application of Zinc Oxide Varistors”, J. Am. Ceram. Soc. 73 (1990) 1817 – 1840.
25. Donald A. Neamen, “Fundamentals of Semiconductor Physics and Devices”, p343－346.
26. T. K. Gupta, and W. G. Carlson, “A Grain Boundary Defect Model for Instability/Stability of ZnO Varistor”, J. Mater. Sci., 20 (1985) 3487-3500.
27. G. E. Pike, “Electronic of ZnO varistor: A New Model”, p369-377 in “Grain boundaries in Semiconductor” Edited by H. J. Leamy, G. E. Pike and C. H. Seager North Holland Pulishing Co. New York (1982)
28. 林予順，「氧化鋅變阻器之缺陷研究」，國立交通大學電子物理學所，碩士論文 (1995)。
29. K. Mukae, K. Tsuda, and I. Nagasawa, “Capacitance-vs-voltage characteristics of ZnO varistors”, J. Appl. Phys., 50 (1979) 4475-4476.
30. Y. C. Chen, C. Y. Shen, H. Z. Chen, Y. F. Wei， and L. Wu “Grain Growth and Electrical Properties in ZnO Varistors with Various Valence States of Additions’’, J. Jour. Appl. Phys. 30 (1991) 84-90
31. C. N. Turton, and T. I. Turton, The oxide handbook, ed. G. V. Samsonov, IFI/Plenum, New York, 1973, pp 378 – 379.
32. Y. Yano, Y. Takai, and H. Moroka, “Interface States in ZnO Varistor with Mn, Co, and Cu impurities”, J. Mater. Res. 9 (1994) 112 – 118.
33. Y. Chen, C. Shen, and L. Wu, “Grain Growth Processes in ZnO Varistors with Various Valence States of Manganese and Cobalt”, J. Appl. Phys. 62 (1991) 8363 – 8367
34. T. R. N. Kutty, and S. Ezhilvalavan, “Influence of Alkali Ions in Enhancing the Nonlinearity of ZnO-Bi2O3-Co3O4 Varistor Ceramics ’’, Jpn. J. Appl. Phys. , 34 (1995) 6125 – 6132.
35. E. Olsson, and G. L. Dunlop, “Development of Interfacial Microstructure During Cooling of a ZnO Varistor Material.”, J. Appl. Phys. 66 (1989) 5072-5077.
36. Y. M. Chiang, J. R. Lee, and H. Wang, in Ceramic Microstructure Control at the Atomic Level, edited by A. P. Tomosia, and A. Glaeser, Plenum Press, New York, (1988) p131-147.
37. M. R. C. Santos, P. R. Bueno, E. Longo, and J. A. Varela, “Effect of Oxidizing and Reducing Atmospheres on the Electrical Properties of Dense SnO2-Based Varistors”, J. Europ. Ceram. Soc. 21 (2001) 161 – 167.
38. C. W. Nahm, “Effect of Cooling Rate on Electrical Properties and Stability of ZPCCY-Based Varisor Ceramics”, Mater. Chem. Phys. 82 (2003) 726-732.

39. C. W. Nahm, and H. S. Kim, “Influence of Cooling Rate on Stability of Nonlinear Properties of ZnO-Pr6¬O11-Based Varistor Ceramics” Mater. Lett. 57 (2003) 1544-1549.
40. C. W. Nahm, “Effect of Cooling Rate on Degradation Characteristics of ZnO-Pr6¬O11-CoO-Cr2O3-Y2O3-Based Varistors”, Solid State Comm. 132 (2004) 213-218.
41. P. Durán, F. Capel, J. Tartaj, and C. Moure“Low-Temperature Fully Dense and Electrical Properties of Doped-ZnO Varistors by a Polymerized Complex Method”, J. Europ. Ceram. Soc. 22 (2002) 67-77.