具有巨大應變的BNT-based 固溶材料近期內已被大家廣泛研究。然而，形成巨大應變量的成因至今仍有分歧，Zhang 等人認為應變的貢獻主要來自於鐵電與反鐵電相之間的轉變；Teranishi 等人利用外加電場下的X-ray繞射行為，認為大應變量歸因於長方晶相(Tetragonal phase)內90o電域(domain)的轉換。
本實驗利用傳統固態氧化物法備製BNT-xBT (x=3、6、9)壓電陶瓷系統，並藉由量測其結晶結構、形貌、介電、壓電及電場誘發應變，分析材料相變化以及應變量的關聯性。解釋了BNB6T因為6mol% Ba2+的添加降低了去極化溫度，而造成P-E曲線呈現寬變窄的現象。再者，隨溫度增加P-E越趨近反鐵電特性而應變量差異不大，結果顯示BNB6T具有低溫度敏感性的應變量，表示此材料具有良好的應用溫度範圍。另外，由BNB3T、BNB6T、BNB9T三者應變量的比較，認為一個具有大應變特性時，矯頑電場值(Ec)不是主要考量因素，而是材料最大極化值(Pmax)。另一方面，我們採用BNB6T為基材進行2mol% B-site取代， XRD繞射圖中顯示幾乎沒有峰值偏移與強度變化，表示此少量取代並沒有對整體晶體結構造成太大改變，原因可能為B-site本身離子半徑較小(約60pm)所致。然而，相似結構卻具有鐵電或是反鐵電兩種不同的電性表現，藉由升溫介電量測結果發現，去極化溫度與P-E曲線具有相同趨勢，顯示材料相變點的改變以及材料鍵結表現對鐵電特性具有巨大的影響。
比較本實驗設計A-site & B-site的取代，藉由兩種不同的方式影響BNT-xBT材料系統。添加離子半徑較大的A-site元素能調整材料結構，而小離子半徑的B-site元素添加能改變鐵電材料的缺陷形態，此兩種方式皆能提供一個可回復性的晶域轉換。此現象將有助於維持電場誘發應變時，體積膨脹與收縮的反覆行為。

Giant strain BNT-based solid solution material has been extensively studied recently. However, the origin of formation of large stain is still diverse. Zhang et al. believe that the very large strain is attributed to the structural phase transition between anti-ferroelectric and ferroelectric. However, Teranishi et al. suggested that the very large strain is due to 90°-domain switching in the tetragonal phase observed by the x-ray diffraction under a high electric field.
In this case, lead-free piezo-ceramics BNT-xBT (x=3、6、9) were synthesized by a conventional ceramic fabrication process, and we investigated the connection between phase transformation and giant strain properties by observing crystal structures, dielectric properties, field-induced strain properties. Results show the necking phenomenon of (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNB6T) due to lower the depolarization point by adding 6mol% Ba2+. Further, results also show that BNB6T processes wide application temperature range, and exhibits a low temperature dependent strain properties. Besides, we suggest Pmax is one of important consideration for estimating a material whether with giant strain by comparison of the strain properties of BNB3T, BNB6T and BNB9T. On the other hand, we try to substitute 2mol% Ti4+ to adjust ferroelectric properties. The XRD data of BNB6T with 2mol% B-site doping exhibit no peak shifting but the electric properties show different ferroelectric behavior. However, the P-E curve exhibit ferroelectric or antiferroelectric properties with similar structure, indicating the necking behavior of the P-E curve could be attributed to depolarization point shifting and bounding characteristics.
We observe that A-site and B-site dopants show different influences on electric properties. Using A-site doping, crystal structure of BNB6T ceramics were modified because of the large ionic radiation of Ba2+. On the other hand, B-site doping may alter the defect states of ferroelectrics. A-site and B-site doping may contribute to a reversible domain switching and good for maintaining the field-induced strain behavior.

1.Q. Xu, X. L. Chen, W. Chen, M. Chen, S. L. Xu, B. H. Kim, and J. H. Lee, “Effect of MnO addition on structure and electrical properties of 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 ceramics prepared by citrate method,” Materials Science and Engineering B, 130, 94 (2006).
2.T. Takenaka and H. Nagata, “Current status and prospects of lead-free piezoelectric ceramics,” Journal of the European Ceramic Society, 25, 2693 (2005).
3.Z. Yu, C. Ang, R. Guo, and A. S. Bhalla, “Piezoelectric and strain properties of Ba(Ti1-xZrx)O3 ceramics,” Journal of Applied Physics, 92, 1489 (2002).
4.Y. Yuan, S. Zhang, X. Zhou, and J. Liu, “Phase transition and temperature dependences of electrical properties of [Bi0.5(Na1-x-yKxLiy)0.5]TiO3 ceramics,” Japanese Journal of Applied Physics, 45, 831 (2006).
5.X. X. Wang, S. H. Choy, X. G. Tang, and H. L. W. Chan, “Dielectric behavior and microstructure of (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-BaTiO3 lead-free piezoelectric ceramics,” Journal of Applied Physics, 97, 1 (2005).
6.Y. Hosono, K. Harada, and Y. Yamashita, “Crystal growth and electrical properties of lead-free piezoelectric material (Na1/2Bi1/2)TiO3-BaTiO3,” Japanese Journal of Applied Physics, 40, 5722 (2001).
7.A. Sasaki, T. Chiba, Y. Mamiya, and E. Otsuki, “Dielectric and piezoelectric properties of (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3 systems,” Japanese Journal of Applied Physics, 38, 5564 (1999).
8.Y. Makiochi, R. Aoyagi, Y. Hiruma, H. Nagata, and T. Takenakd, “(Bi1/2Na1/2)TiO3-(Bi0.5K0.5)TiO3-BaTiO3 Based Lead-Free Piezoelectric Ceramics,” Japanese Journal of Applied Physics, 44, 4350 (2005).
9.T. Takenaka and H. Nagata, “Current status and prospects of lead-free piezoelectric ceramics,” Journal of the European Ceramic Society, 25, 2693 (2005).
10.T. Takenaka, K. I. Maruyama, and K. Sakata, “(Bi1/2Na1/2)TiO3-BaTiO3 system for lead-free piezoelectric ceramics,” Japanese Journal of Applied Physics, 30, 2236 (1991).
11.M. Kimura, A. Ando, T. Sawada, and K. Hayashi, “Piezoelectric ceramic composition and piezoelectric ceramic device using the same,” U.S. Pat. , 6258291, (2001).
12.T. Takenaka, M. Hirose, and K. Miyabe, “Piezoelectric ceramic composition,” U.S. Pat., 6004474, (1999).
13.T. Takenaka, “Dielectric ceramic composition,” U.S. Pat., 5637542, (1997).
14.M. Kimura, T. Ogawa, and A. Ando, “Piezoelectric ceramic composition,” U.S. Pat., 6093339, (2000).
15.Murata Manufacturing Co., Ltd., Japan Pat., 56778, (2006).
16.Murata Manufacturing Co., Ltd., Japan Pat., 3259677, (2005).
17.TDK, Japan Pat., 2942535, (2005).
18.TDK, Japan Pat., 082422, (2005).
19.Taiyo Yuden, Japan Pat., 75449, (2004).
20.Kyocera, Japan Pat., 34574, (2003).
21.E. Cross, “Lead-free at last,” Nature, Vol. 432, 24 (2004).
22.Y. Saito, H. Takao, T. Tani, T. Nonoyama, K. Takatori, T. Homma, T. Nagaya, and M. Nakamura, “Lead-free piezoceramics,” Nature, Vol. 432, 84 (2004).
23.K. Uchino and S. Nomura, “Electrostriction in PZT-family antiferroelectrics,” Ferroelectrics, 50, 517 (1983).
24.W. Y. Pan, C. Q. Dam, Q. M. Zhang, and L. E. Cross, “Large displacement transducers based on electric field forced phase transitions in the tetragonal (Pb0.97La0.02) (Ti,Zr,Sn)O3 family of ceramics,” Journal of Applied Physics, 66, 6014 (1989).
25.S. T. Zhang, A. B. Kounga, E. Aulbach, H. Ehrenberg, J. Rödel, “Giant strain in lead-free piezoceramics Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 system,” Applied Physics Letters, 91, 112906 (2007).
26.S. Teranishi, M. Suzuki, J. Noguchi, M. Miyayama, C. Moriyoshi, Y. Kuroiwa, “Giant strain in lead-free (Bi0.5Na0.5)TiO3 -based single crystals,” Applied Physics Letters, 92, 182905 (2008).
27.Y. Hiruma, H. Nagata, T. Takenaka, “Phase diagrams and electrical properties of (Bi1/2Na1/2)TiO3-based solid solutions,” Journal of Applied Physics, 104, 124106 (2008).
28.Y. Hiruma, H. Nagata, T. Takenaka, “Detection of morphotropic phase boundary of (Bi1/2Na1/2)TiO3-Ba(Al1/2Sb1/2)O3 solid-solution ceramics,” Applied Physics Letters, 95, 052903 (2009).
29.A. Hussain, C. W. Ahn, J. S. Lee, U. Aman, I. W. Kim, “Large electric-field-induced strain in Zr-modified lead-free Bi0.5(Na0.78K0.22)0.5 TiO3 piezoelectric ceramics,” Sensors and Actuators A, 158, 84 (2010).
30.A. Hussain, C. W. Ahn, U. Aman, J. S. Lee, I. W. Kim, “Effects of Hafnium Substitution on Dielectric and Electromechanical Properties of Lead-free Bi0.5(Na0.78K0.22)0.5(Ti1-xHfx)O3 Ceramics,” Japanese Journal of Applied Physics, 49, 041504 (2010).
31.S. T. Zhang, A. B. Kounga, E. Aulbach, T. Granzow, W. Jo, H. J. Kleebe, and J. Rödel, “Lead-free piezoceramics with giant strain in the system Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3 I. Structure and room temperature properties,” Journal of Applied Physics, 103, 034107 (2008).
32.K. N. Pham, A. Hussain , C. W. Ahn, I. W. Kim, S. J. Jeong, J. S. Lee, “Giant strain in Nb-doped Bi0.5(Na0.82K0.18)0.5TiO3 lead-free electromechanical ceramics,” Materials Letters, 64, 2219 (2010).
33.W. Liu , X. Ren, “Large piezoelectric effect in Pb-free ceramics,” Physical Review Letters, 103, 257602 (2009).
34.Z. Xu, X. Dai, and D. Viehland, “Impurity-induced incommensuration in antiferroelectric La-modified lead zirconate titanate,” Physical Review Letters, 51, 6261 (1995).
35.A. M. Glazer, “Simple ways of determining perovskite structure,” Crystallographica, A31, 756 (1975).
36.W. H. Lee, W. A. Groen, H. Schreinemacher and D. Hennings, “Dysprosium doped dielectric materials for sintering in reducing atmospheres,” Journal of Electroceramics, 5[1], 31 (2000).
37.Olaf Muller, The Major Ternary Structural Families, Springer-Verlag, Berlin, (1974).
38.N. Setter and L. E. Cross, “The contribution of structural disorder to diffuse phase transitions in ferroelectrics,” Journal of Materials Science, 15, 2478 (1980).
39.N. Setter and L. E. Cross, “The role of B-site cation disorder in Diffusion phase transition behavior of perovskite ferroelectrics,” Journal of Applied Physics, 51[8], 4356 (1980)
40.C. Kittel, Introduction to solid state physics, 7th Ed., John Wiley and Sons, Inc.,New York, (1996).
41.T. Oh, M. H. Kim, “Phase relation and dielectric properties in (Bi1/2Na1/2)1−x BaxTiO3TiO3 lead-free ceramics,” Materials Science and Engineering B, 132, 239 (2006).
42.D. Viehland, S. J. Jang, and L. Eric Cross, “Freezing of the polarization fluctuations in lead magnesium niobate relaxors,” Journal of Applied Physics, 68 [6], 2916 (1990).
43.G. A. Smolenskii and A. I. Agranovskaya, “Dielectric polarization of a number of complex compounds,” Soviet physics Solid state, 1[10], 1429 (1960).
44.D. Viehland , J. F. Li , S. J. Jang , and L. Eric Cross, “Dipolar-glass model for lead magnesium niobate,” Physics Review B, 43, 8316 (1991)
45.W. Jo, T. Granzow, E. Aulbach, J. Rödel, and D. Damjanovic, “Origin of the large strain response in (K0.5Na0.5)NbO3-modified (Bi0.5Na0.5)TiO3–BaTiO3 lead-free piezoceramics,” Journal of Applied Physics, 105, 094102 (2009).
46.X. Ren, “Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching,” nature materials, 3, 91 (2004).