臺灣博碩士論文加值系統

本研究以檸檬酸先趨物法製備具磁性的MnFe2O4和(Mn,Zn)Fe2O4陶瓷粉體。研究過程中探討起始溶液於不同pH值和Zn2+與Mg2+添加量對粉體特性之影響。首先配製所需金屬離子之硝酸鹽水溶液並加入檸檬酸來產生溶液中金屬離子的鏊合反應，再以氨水調整pH值並加入乙二醇加熱至353K使其持續進行酯化反應。所得酯化物經393K乾燥後再以623K熱處理將酯化物分解並製得到MnFe2O4粉體。製得粉體以XRD、TEM和SEM來作特性分析。實驗結果指出在任何的pH值與不同添加物之添加量下，於623K熱處理後皆可得到單一的MnFe2O4結晶相態。當熱處理溫度提昇至873K後，因為MnFe2O4中的Mn2+於空氣中氧化成Mn3+造成相分離的產生。利用Zn2+與Mg2+的添加可以有效的減緩Mn2+的氧化，因Zn2+與Mg2+的添加可以增加結構中的點缺憾。此研究當中具有較好磁性性質的製程條件為添加5﹪Mg2+。以檸檬酸先趨物法製備之粉體為次微米級的粒子，且粉體經由真空燒結後分析得知此粉體具有良好的燒結能力，於1273K即可燒結。

A citric acid precursor method was used to prepare MnFe2O4 and (Mn,Zn)Fe2O4 particles. Citric acid was added into an aqueous solution, containing nitrates of iron, manganese, or zinc in stoichiometric ratios to form the required ferrites, to chelate the metallic ions. The pH values of starting aqueous solutions were adjusted using NH4OH. After adding glycol into the solution and raising the solution temperature to 353 K, esterification caused the formation of the required solid precursors. The dried solid precursors so obtained were then pyrolyzed to form the corresponding oxides. The characteristics of the obtained solid powders were studied using XRD, TEM, and SEM. Crystalline submicron MnFe2O4 powders were obtained at 623 K for all pH values of the starting solutions used. In air, Mn2+ in MnFe2O4 powder was oxidized to form Mn3+ at temperatures about 873 K, resulting in phase segregation. The addition of Zn2+ or Mg2+ in the starting solution effectively, in some extent, prevented the oxidation of Mn2+. The addition of Zn2+ and Mg2+ may create and increase point defects in the ferrite structure, by forming the Mn2+-Zn2+-oxide and Mn2+-Mg2+-oxide solid solution, and slow down the oxidation process of Mn2+ in air. The best composition in preparing MnFe2O4 with good soft magnetic properties is the one with 5% Mg2+ additions. Particles obtained by citric acid precursor method have high sinterbility and MnFe2O4 powder can be sintered at 1273 K in vacuum.

CONTENTS
CONTENTS OF FIGURES Ⅳ
CONTENTS OF TABLES Ⅷ
CHAPTER 1 INTRODUCTION 1
CHAPTER 2 LITERATURE REVIEW 3
2-1 STRUCTURE OF SPINEL FERRITES 3
2-2 FERRITE POWDER PREPARATION 6
2-2-1 Conventional Method
(solid-state reactions) 6
2-2-2 Citric Acid Precursor Method 7
2-2-3 Coprecipitation Method 8
2-2-4 Hydrothermal Method 9
2-2-5 The Effect of Additions 9
CHAPTER 3 EXPERIMENTAL
TECHNIQUES 11
3-1 EXPERIMENTAL 11
3-1-1 Starting Solutions 11
3-1-2 Chelating and Esterification 11
3-1-3 Drying 12
3-1-4 Pyrolysis 12
3-1-5 Heat Treatment 12
3-1-6 Sintering 12
3-2 CHARACTERISTIC ANALYSIS 13
3-2-1 X-ray Diffraction 13
3-2-2 Scanning Electron Microscopy 14
3-2-3 Transmission Electron Microscopy 14
3-2-4 Gas Pyenometer 15
CHAPTER 4 RESULTS AND
DISCUSSION 20
4-1 Mn-Fe-O SYSTEMS 20
4-1-1 The effects of Zn2+ additions 21
4-1-2 The effects of Mg2+ additions 22
4-2 Mn-Zn-Fe OXIDES SYSTEM 24
4.3 MAGNETIC PROPERTIES 25
4.4 SINTERBILITY 25
CHAPTER 5 CONCLUSION 54
REFERENCES 55
APPENDIX A 59
APPENDIX B 81

REFERENCES
1. T. Takei, Theory and application of ferrites, Maruzen, Tokyo, Japan, 1960.
2. L. Néel, “Magnetic properties of ferrites: ferrimagnetism and antiferromagnetism,” Ann. Phys., 3, 137-65 (1948).
3. Q. Chen, A. J. Rondinone, B. C. Chakoumakos, and Z. J. Zhang, “Synthesis of superparamagnetic MgFe2O4 nanoparticles by coprecipitation,” J. Magn. Magn. Mater., 194, 1-7 (1999).
4. Z. X. Tang, C. M. Sorensen, K. J. Klabunde, and G. C. Hadjipanayis, “Preparation of manganese ferrite fine particles from aqueous solution,” J. Colloid. Interface Sci., 146, 38-51 (1991).
5. S. Rajendran, and V. S. Rao, “An anomalous behaviour in the phase stability of the system Fe2O3 and NiO,” J. Mater. Sci., 29, 5673-5679 (1994).
6. R. V. Upadhyay, K. J. Davies, S. Wells, and S. W. Charles, “Preparation and characterization of ultra-fine MnFe2O4 and MnxFe1-xO4 spinel systems: II. Magnetic fluids,” J. Magn. Magn. Mater., 139, 249-254 (1995).
7. S. P. Chaudhuri and I. Roy, “Preparation and identification of some ferrites in Ni-Co-Mn-Zn system,” British Ceramic Transaction, 94, 250-253 (1995).
8. C. H. Chao and P. D. Ownby, “Ultrasonic spray pyrolysis of a chelated precursor into spherical YBa2Cu3O7-x high temperature superconductor powders.” J. Mater. Sci., 30, 6136-6144 (1995).
9. E. Lucchini and S. Meriani, “A new method for low temperature preparation of barium hexaferrite powders,” J. Mater. Sci., 19, 121-124 (1984).
10. M. C. D´Arrigo, C. Leonelli, and G. C. Pellacani, “Microwave-hydrothermal synthesis of nanophase ferrites,” J. Am. Ceram. Soc., 81, 3041-3043 (1998).
11. W. H. Lin, S. K. J. Jean, and C. S. Hwang, “Phase formation and composition of Mn-Zn ferrite powders prepared by hydrothermal method,” J. Mater. Res., 14, 204-208, (1999).
12. C. W. Chang, Y. S. Hong, S. J. Wang, and I. N. Lin, “Characteristics of MnZn-ferrite powders prepared by novel techniques,” Chin. J. Mater. Sci., 23, 62-71 (1991).
13. W. Zhong, W. Ding, Y. Jiang, N. Zhang, J. Zhang, Y. Du, and Q. Yan, “Preparation and magnetic properties of barium hexaferrite nanoparticles produced by the citrate process,” J. Am. Ceram. Soc., 80, 3258-3262 (1997).
14. M. A. Willard, Y. Nakamura, D. E. Laughlin, and M. E. McHenry, “Magnetic properties of ordered and disordered spinel-phase ferrimagnets,” J. Am. Ceram. Soc., 82, 3342-3346 (1999).
15. W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, Introduction to ceramics, Wiley, New York, 1976.
16. D. Arcos, R. Valenzuela, M. Vázquez, and M. Vallet-Regi, “Frequency behaviour of Zn-Mn ferrites nanoparticles obtained by high-energy ball milling,” J. Magn. Magn. Mater., 203, 319-321 (1999).
17. Z. Krysicki and T. Lubańska, “Effect of the presintering process on the microstructure and initial permeability of Mn-Zn ferrite,” J. Magn. Magn. Mater., 19, 107-108 (1980).
18. M. Vallet, M. Parras, X. Obradors, M. Pernet, J. Rodriguez, and J. C. Joubert, “Synthesis of sodium-zinc spinel ferrites,” IEEE Transactions on Magnetics, 20, 1515-1516 (1984).
19. J. Ding, P. G. McCormick, and R. Street, “Formation of spinel Mn-ferrite during mechanical alloying,” J. Magn. Magn. Mater., 171, 309-314 (1997).
20. M. U. Rana, M. Islam, and T. Abbas, “The magnetic interaction in Zn-substituted manganese ferrites,” Solid State Communications, 99, 43-45 (1996).
21. M. P. Pechini, U.S. Pat. No. 3330697, July 11, 1967.
22. D. H. A. Blank, H. Kruidhof, and J. Flokstra, “Preparation of YBa2Cu3O7-δ by citrate synthesis and pyrolysis,” J. Phys. D: Appl. Phys., 21, 226-227 (1988).
23. P. Karen and A. Kjekshus, “Citrate-gel syntheses in the Y(O)-Ba(O)-Cu(O) system,” J. Am. Ceram. Soc., 77, 547-552 (1994).
24. H. K. Lee and D. Kim, “Superconducting transition and Raman spectrum of Y1Ba2Cu3O7-x prepared,” J. Appl. Phys., 65, 2563-2565 (1989).
25. W. J. Lee and T. T. Fang, “The effect of the molar ratio of cations and citric acid on the synthesis of barium ferrite using a citrate process,” J. Mater. Sci., 30, 4349-4354 (1995).
26. A. Verma, T. C. Goel, R. G. Mendiratta, and R. G. Gupta, “High-resistivity nickel-zinc ferrites by the citrate precursor method,” J. Magn. Magn. Mater., 192, 271-276 (1999).
27. S. Prasad and N. S. Gajbhiye, “Magnetic studies of nanosized nickel ferrite particles synthesized by the citrate precursor technique,” Journal of Alloys and Compounds, 265, 87-92 (1998).
28. L. W. Tai and P. A. Lessing, “Modified resin-intermediate processing of perovskite powders: Part I. Optimization of polymeric precursors,” J. Mater. Res., 7, 502-510 (1992).
29. E. Auzans, D. Zins, E. Blums, and R. Massart, “Synthesis and properties of Mn-Zn ferrite ferrofluids,” J. Mater. Sci., 34, 1253-1260 (1999).
30. T. Sato, C. Kuroda, and M. Saito, “Preparation and magnetic characteristics of ultra-fine spinel ferrites,” Proceedings of the International Conference, 72-74 (1970).
31. T. Akashi, I. Sugano, T. Okuda, and T. Tsuji, “Sintering of coprecipitated manganese zinc ferrite powder, Proceedings of the International Conference, 96-98 (1970).
32. P. Ravindranathan and K. C. Patil, “A low temperature path to the preparation of ultrafine ferrites,” Am. Ceram. Soc. Bull., 66, 688-692 (1987).
33. S. Fritsh and A. Navrotsky, “ Thermodynamic properties of manganese oxides,” J. Am. Ceram. Soc., 79, 1761-1768 (1996).
34. J. H. Boy and G. P. Wirtz, “Grain boundary modifications of manganese ferrites,” J. Eur. Ceram. Soc., 14, 227-235 (1994).
35. D. Makovec and M. Drofenik, “Hydrothermal synthesis of Manganese zinc ferrite Powders from Oxides,” J. Am. Ceram. Soc., 82, 1113-1120 (1999).