本研究以傳統固態反應法製備氧化鋅變阻器ZnO-Pr6O11-Co3O4，並探討添加微量氧化鐵(Fe2O3)對微結構與變阻性質之影響。由顯微結構觀察發現添加適量的Fe2O3時可以使PrOx均勻的分佈在晶界上，此現象能夠促使氧離子更均勻的吸附於晶界上進而提升變阻性質。此外，實驗中藉由阻抗分析計算晶界能障高度，結果顯示當氧化鐵添加量為0.001mol%時，能夠使晶界能障高度上升，有助於提升變阻性質。但若添加量增加至0.005mol%時，大量的PrOx則會富集在triple point，且生成少量的二次相ZnFe2O4，而使變阻性質劣化。

In this study, ZnO-Pr6O11-Co3O4 based varistors were prepared using a conventional solid-state reaction and sintering process. The effects of Fe2O3 addition on the microstructure and varistor properties were investigated. PrOx phases were found to locate at grain-boundaries uniformly as proper amount of Fe2O3 was added. This will promote the diffusion and chemisorptions of excess oxygen ions at the grain-boundaries, which enhances the varistor property. The energy barrier heights of the grain-boundary for the samples were measured using impedance spectroscopy and observed that when the Fe2O3 addition concentration was increased to 0.001mol%, the barrier height can be increased, which improved the varistor behavior. However, as the addition concentration of Fe2O3 was increased above 0.005mol%, most PrOx phase(s) were found to locate at the triple points, and form the second phase, ZnFe2O4, which resulted in the deterioration of the varistor property.

1. F. OBA, I. TANAKA and H. ADACHI, “Effect of Oxidation on Chemical Bonding around 3d Transition-Metal Impurities in ZnO”, Jpn. J. Appl. Phys. 38, 3569-3575(1999)
2. T. K. Gupta, “Application of Zinc Oxide Varistors”, J. Am. Cerum. Soc., 73, 1817-1840 (1990)
3. 國立編譯館、邱碧秀，「電子陶瓷材料」，徐氏基金會出版。197-239(1988)
4. 吳朗，「電子陶瓷－半導體」，全欣資訊。169-213(1994)
5. A. J. Moulson, and J. M. Herbert, “Electroceramics Materials Properties Applications”, London, Chapman and Hall ,New York, 131(1990).
6. S. Y. Chun, H. Funakubo, K. Shinozaki, N. Mizutani and N. Wakiya, “Phase Diagram and Microstructire in the ZnO-Pr2O3 System”, J. Am. Ceram. Soc., 80, 4, 995-998 (1997)
7. C.W. Nahm, “Electrical Properties and Stability of Praseodymium Oxide-Based ZnO Varistor Ceramics Doped with Er2O3”, J. Europ. Ceram. Soc. 23, 9, 1345-1353 (2003)
8. T. K. Gupta, “Application of Zinc Oxide Varistors”, J. Am. Ceram. Soc. 73, 7, 1817 – 1840 (1990)
9. G. E. Pike, “Electronic of ZnO varistor: A New Model”, 369-377 in “Grain boundaries in Semiconductor” , ed H. J. Leamy, G. E. Pike and C. H. Seager North Holland Pulishing Co. New York (1982).
10. T. K. Gupta, and W. G. Carlson, “A Grain Boundary Defect Model for Instability/Stability of ZnO Varistor”, J. Mater. Sci., 20, 3487-3500 (1985)
11. K. Mukae, K. Tsuda, and I. Nagasawa, “Non-Ohmic Properties of ZnO-Rare Earth Metal Oxide-Co3O4 Ceramics”, Jpn. J. Appl. Phys., 16, 8, 1361-1368, (1977)
12. D. R. Clarke, ”Varistor Ceramics”, J. Am. Ceram. Soc., 82, 3, 485-502, (1999)
13. M. Sida, S. Y. Chun, N. Wakiya, K. Shinozaki and N. Mizutani, “Effect of the sintering temperature and atmosphere on the grain growth and grain boundary phase formation of Pr-doped ZnO varistor” J. Ceram. Soc. Jpn., 104, 1, 45 – 49 (1996)。
14. A. B. Alles, and V. L. Burdick “The Effect of Liquid-Phase Sintering of Pr6O11-Based ZnO Varistors”, J. Appl. Phys., 70, 11, 6883-6890 (1991)
15. 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, 8, 2098-2102 (1993)
16. 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, 9, 2379-2384 (1996)
17. N. Wakiya, S. Y. Chun, K. Shinozaki, and N. Mizutani “Redox Reaction of Praseodymium Oxide in the ZnO Sintered Ceramics”, J. Sol. Stat. Chem., 149, 349-353 (2000)
18. C. W. Nahm, “Effect of Cooling Rate on Degradation Characteristics of ZnO-Pr6¬O11-CoO-Cr2O3-Y2O3-Based Varistors”, Sol. Stat. Comm., 132, 213-218 (2004)
19. 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, 4, 995-998(1997)
20. 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, 15-23 (1999)
21. 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, 379-385 (2002)
22. C. W. Nahm, “Influence of Praseodymium Oxide/Cobalt Oxide Ratio on Microstructure and Electrical of Zinc Oxide Varistor Ceramics”, Mater. Chem. Phys., 80, 746-751(2003)
23. T.R.N. Kutty and S. Ezhilvalavan, “The influence of Bi2O3 non- stoichiometry on the non-linear property of ZnO varistors”, Mater. Chem. Phys., 38, 267–276(1994)
24. C. N. Turton and T. I. Turton, “The oxide handbook”, ed. G. V. Samsonov, IFI/Plenum, New York, 378 – 379(1973)
25. Y. Yano, Y. Takai, and H. Moroka, “Interface States in ZnO Varistor with Mn, Co, and Cu impurities”, J. Mater. Res., 9, 1, 112 – 118 (1994)
26. Y. Chen, C. Shen, and L. Wu, “Grain Growth Processes in ZnO Varistors with Various Valence States of Manganese and Cobalt”, J. Appl. Phys., 69, 12, 8363 – 8367(1991)
27. T. Watari and R.C. Bradt, ”Grain growth of sintered ZnO with alkali oxide additions”, J. Ceram. Soc. Jpn., 101, 1085–1089(1993)
28. W. Heywang, “Resistivity Anomaly in Doped Barium Titanate “J. Am. Ceram. Soc., 47, 10, 484 – 490 (1964)
29. K.Mukae, K. Tsuda and I. Nagasawa, “Capacitance-vs-voltage characteristics of ZnO varistors” J. Appl. Phys., 50, 6, 4475 – 4476(1979)
30. 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)。
31. E. D. Guth, J. R. Holden, N. C. Baenziger and L. Eyring”Praseodymium Oxides. II. X-Ray and Differential Thermal Analyses”, 76, 5239 – 5242 (1954)
32. M. R.C. Santos, P. R. Bueno, E. Longo, J. A. Varela” Effect of oxidizing and reducing atmospheres on the electrical properties of dense SnO2-based varistors” J. Europ. Ceram. Soc., 21, 161-167(2001)
33. R. Hansson, P.C. Hayes, and E. Jak, “Phase equilibria in the Fe-Zn-O system at conditions relevant to zinc sintering and smelting”, Mineral Processing and Extractive Metallurgy, 14, 3, 141-146(2004)