鈦酸鋇陶瓷體之居里溫度約在130℃，在溫度超過居里溫度後，其介電常數會急遽下降，無法滿足車用陶瓷電容器對電容溫度係數之要求(X8R: -55～+150℃温度範圍内，電容量變化率小於±15％)。文獻中指出共同添加Nb和Co於鈦酸鋇中可使其介電常數隨溫度變化之曲線平坦化，而達到X7R規格。因此本研究首先藉由添加5mol% Bi0.5Na0.5TiO3(BNT) 於BaTiO3中，使居里溫度提高至150℃以上，並添加Nb和Co於基質中，同時改變添加劑之Nb/Co比，探討其對結晶相、微結構、介電性質之影響。研究發現添加少量的BNT至純鈦酸鋇中，的確可以有效提升鈦酸鋇之居里溫度，當添加5mol% 時，不但可促進BaTiO3陶瓷體之緻密化，使晶粒成長受到抑制，居里溫度亦將提高至150℃以上。共同添加Nb和Co且添加劑Nb/Co=3的BaTiO3-BNT試片其介電常數之溫度係數最小，且介電常數皆在2000以上。並由TEM證實晶粒內部之Nb和Co有濃度分佈不均勻的現象，顯示電容溫度曲線平坦化之機制應為添加劑濃度分佈不均勻所造成之核-殼結構所致。

In this study, we added Bi0.5Na0.5TiO3 (BNT) into the BaTiO3, which enhanced the Curie temperature of BaTiO3. When the addition of BNT is 5mol%, the grain growth is suppressed. Curie temperature increases to 150℃, along with densification of the sample. The literature indicated that added Nb and Co into BaTiO3 for MLCCs resulted in flattening of temperature coefficient of capacitance curve, which meet the X7R specification. So we used 5mol%BNT -95mol%BaTiO3 as matrix, than added Nb and Co into the matrix and controlled Nb/Co ratio. When Nb/Co ratio was 3, the sample had the most flatting temperature coefficient of capacitance curve, and the relative dielectric constant was above 2000. TEM observation revealed that inside the grain, Nb and Co had concentration gradient, core-shell structure is formed. This should be the mechanism of flatting capacitance-temperature curve.

1.邱碧秀，電子陶瓷材料，(1988)。
2.J. Nowotny, “Electronic Ceramic Materials,” (1991).
3.A. J. Moulson and J. M. Herbert, “Electroceramics,” Chapman & Hall, (1990).
4.D. E. Rase and R. Roy, “Phase equilibria in the system BaO–TiO2,” J. Am. Ceram. Soc., 38, [3], 102-113, (1955).
5.R. K. Sharma, N. H. Chan and D. M. Smyth, “Solubility of TiO2 in BaTiO3,” J. Am. Ceram. Soc., 64, [8], 448-451, (1981).
6.Y. H. Hu, M. P. Harmer and D. M. Smyth, “Solubility of BaO in BaTiO3,” J. Am. Ceram. Soc., 8, [7], 372-376, (1985).
7.K. W. Kirby and B. A. Wechsler, “Phase relations in the barium titanate—titanium oxide system,” J. Am. Ceram. Soc., 74, [8], 1841-1847, (1991).
8.A. K. Maurice and R. C. Buchanan, “Preparation and stoichiometry effects on microstructure and properties of high purity BaTio3,” Ferroelectrics, 74 , 61-75, (1987).
9.J. D. Murray, Am. Ceram. Soc. Bull., 37 , 476-479, (1958)
10.A. Beauger, J. C. Mutin and J. C. Niepce, “Role and behavior of orthotitanate Ba2TiO4 during the processing of BaTiO3 based ferroelectric,” J. Mater. Sci., 19, 195-201, (1984).
11.J. K. Lee and K. S. Hong, “Role of Ba/Ti ratios in the dielectric properties of BaTiO3 ceramics,” J. Am. Ceram. Soc., 84, [9], 2001-2006, (2001).
12.G. A. Smolenskii and A. I. Agranovskaya, “Dielectric polarization of a number of complex compounds,” Sov. Phys., Solid State (Engl. Transl.), 1, [10], 1429-1437, (1960).
13.Y. Lin, “Effects of Eu2O3 on the phase transformation and piezoelectric properties of Na0.5Bi0.5TiO3-based ceramics,” J. Mater. Sci., B, [99], 449-452, (2003).
14.H. Nagata and T. Takenaka, “Lead- free piezoelectric ceramics of Bi1/2Na1/2TiO3-KNbO3-1/2(Bi2O3*Sc2O3) system,” Jpn. J. Appl. Phys., 37, 5311-5314, (1998).
15.Y Huang, L Gao, Y Hu, H Du, “Compositional effects on the properties of (1-x)BaTiO3-xBi0.5Na0.5TiO3 ceramics,” J Mater Sci: Mater Electron, (2007).
16.W. D. Kingery, H. K. Bowen and D. R. Uhlmann, “Introduction to Ceramics,” 2nd Edition , John Wiley & Sons , New York, (1976).
17.G. Arlt , D. Hennings and G. With, “Dielectric properties of fine-grained barium titanate ceramics,” J. Appl. Phys., 58, 1619-1625, (1985).
18.K. Uchino, E. Sadanaga and T. Hirose, “Dependence of the crystal structure on particle size in barium titanate,” J. Am. Ceram. Soc., 72, [8], 1555-1558, (1989).
19.D. Hennings, Int. J. High Tech. Ceram. 3, 91-111, (1987).
20.M. W. Barsoum, “Fundamentals of Ceramics,” 513-543, (1997).
21.J. M. Herbert, “Ceramic Dielectrics and Capacitors,” New York, 202-218, (1985).
22.J. N. Lin and T. B. Wu, “Effect of isovalent substitutions on lattice softening and transition character of BaTiO3 solid solutions,” J. Appl. Phys., 68, 985-993, (1990).
23.H. Ihrig, “The phase stability of BaTiO3 as a function of doped 3d element: an experimental study,” J. Phys. C: Solid State Phys., 11, 819-827, (1978).
24.D. Hennings and A. Schnell, “Diffuse ferroelectric phase transitions in Ba(Ti1-yZry)O3 ceramics,” J. Am. Ceram. Soc., 65, [11], 539-534, (1982).
25.Z. Q. Zhuang, Mat. Res. Bull., 22, 1329-1335, (1987).
26.薛志宗，不同製程之鈣添加鈦酸鋇的還原氣氛抵抗能力的研究，國立成功大學材料科學與工程研究所碩士論文，(1997)。
27.Kishi-H, Kohzu-N, Sugino-J, Ohsato-H, Iguchi-Y, Okuda-T, J. European Ceram.Soc., 19, 6-7, 1043-1046,(1999).
28.Y. S. Jung, E. S. Na, U. Paik, J. Lee and J. Kim, “A study on the phase transition and characteristics of rare earth element doped BaTiO3,” Mater. Res. Bull., 37, 1633-1640, (2002).
29.E. Na, S. C. Choi and U. Paik, “Temperature dependence of dielectric properties of rare-earth element doped BaTiO3,” J. Ceram. Pro. Res., 4, [4], 181-184, (2003).
30.Y. Li, X. Yao and L. Zhang, “High permittivity neodymium-doped barium titanate sintered in pure nitrogen,” Ceram. Inter., 30, 1325-1328, (2004).
31.Y. H. Song and Y. H. Han, “Effects of rare-earth oxides on temperature stability of acceptor-doped BaTiO3,” Jpn. J. Appl. Phys., 44, [8], 6143-6147, (2005).
32.S. Sato, Y. Fujikawa and T. Nomura, “Effect of rare-earth doping on the temperature-capacitance characteristics of MLCCs with Ni electrodes,” Dielectric Materials and Devices, 473-481, (2000).
33.S. Wang, S. Zhang, X. Zhou, B. Li and Z. Chen, “ Effect of sintering atmosphere on the microstructure and dielectric properties of Yb/Mg co-doped BaTiO3 ceramics,” Mater. Lett., 59, 2457-2460, (2005).
34.Y. H. Song, J. H. Hwang and Y. H. Han, “Effect of Y2O3 on temperature stability of acceptor-doped BaTiO3,” Jpn. J. Appl. Phys., 44, [3], 1310-1313, (2005).
35.Y. H. Song and Y. H. Han, “Effects of rare-earth oxides on temperature stability of acceptor-doped BaTiO3,” Jpn. J. Appl. Phys., 44, [8], 6143-6147, (2005).
36.S. Wang, S. Zhang, X. Zhou, B. Li and Z. Chen, “Investigation on dielectric properties of BaTiO3 co-doped with Ni and Nb,” Mater. Lett., 60, 909-911, (2006).
37.N. Setter and L. E. Cross, “The role of B-site cation disorder in diffuse phase transition behavior of perovskite ferroelectrics,” J. Appl. Phys., 51, [8], 4356-4360, (1980).
38.G. A. Smolenskii, A. I. Agranovskaya and V. A. Isupov, “New ferroelectrics of complex compound,” Sov. Phys. Solid State., 1, 907-908, (1959).
39.D. Hennings and R. Rosenstein, “Temperature-stable dielectrics based on chemically inhomogeneous BaTiO3,” J. Am. Ceram. Soc., 67, [4], 249-254, (1984).
40.H. Y. Lu, J. S. Bow and W. H. Deng, “Core-shell structure in ZrO2-modified BaTiO3 ceramics,” J. Am. Ceram. Soc., 73, [12], 3562-3568, (1990).
41.H. T. Martirena and J. C. Burfoot, “Grain-size effects on properties of some ferroelectric ceramics,” J. Phys., c7, 3182-3192, (1974).
42.W. R. Beussem, L. E. Cross and A. K. Goswami, “Phenomenological theory of high permittivity in fine-grained barium titanate,” J. Am. Ceram. Soc., 49, [1], 33-36, (1966).
43.P. Murugaraj, T. N. Kutty and M. S. Rao, “Diffuse phase transformation in neodymium-doped BaTiO3 ceramics,” J. Mater. Sci., 21, 3521-3527, (1986).
44.L. Benguigui and K. Bethe, “Diffused phase transition in BaxSr1-xTiO3 single crystal,” J. Appl. Phys., 47, [7], 2787-2791, (1976).
45.D. Bard, E. Barbulescu and A. Barbulescu, “Diffuse phase transitions and ferroelectric-paraelectric diagram for the BaTiO3-SrTiO3 system,” Phys. Stat. Sol. (a), 74, 79-83, (1982).
46.T. R. Armstrong, L. E. Morgens, A. K. Maurice and R. C. Buchanan, “Effects of zirconia on microstructure and dielectric properties of barium titanate ceramics,” J. Am. Ceram. Soc., 72, [4], 605-611, (1989).
47.H. Chazono and H. Kishi, “Sintering characteristics in BaTiO3-Nb2O5-Co3O4 ternary system: I, electrical properties and microstructure,” J. Am. Ceram. Soc., 82, [10], 2689-2697, (1999).
48.H. Chazono and H. Kishi, “Sintering characteristics in BaTiO3-Nb2O5-Co3O4 ternary system: II, stability of so-called ‘core-shell’ Structure,” J. Am. Ceram. Soc., 83, [1], 101-106, (2000).
49.S. K. Chiang, W. E. Lee, and D. W. Readey, “Core-shell structure in doped BaTiO3,” Ceram. Bull., 66 [8] 1230, (1987).
50.G. Liu, X. Wang, Y. Lin, L. T. Li and C. W. Nan, “Growth kinetics of core-shell-structured grain and dielectric constant in rare-earth doped BaTiO3 ceramics,” J. Appl. Phys., 98, 044105, (2005).
51.朱冠宇，組成變化對X8R鈦酸鋇介電陶瓷之介電性質及顯微結構的影響之研究，國立成功大學資源工程研究所碩士論文，(2006)。
52.Y. Mizuno, Y. Okino, N. Kohzu, H. Chazono and H. Kishi, “Influence of the microstructure evolution on electrical properties of multilayer capacitor with Ni electrode,” Jpn. J. Appl. Phys., 37, 5227-5231, (1998).