本研究主要在探討不同鍶鈦比(Sr/Ti ratio)對鈦酸鍶(SrTiO3)其微結構與電性上的差異，分別利用一階段燒結與二階段燒結的方式改變不同熱處裡條件並分析微結構改變晶界形貌的差異，進而解釋晶界工程對材料的重要性。
實驗結果顯示，一階段燒結試片可以看出不同鍶鈦比試片的基本特性:各試片的共位晶界(Σ3-Σ49)比例無明顯差異(皆約在16-17%)。其中Sr/Ti=1.00有最多的Σ3共位晶界(~4%)，其他試片(Sr/Ti=0.91及1.14)約有約2%的Σ3晶界，本實驗由於不同Sr/Ti ratio影響晶界結構，而不能單獨用晶界來解釋，另外介電性質受不同鍶鈦比成分的影響而有所不同，此外二階段燒結的試片有類似的結果。

This study investigates the influences of Sr/Ti ratios for the microstructure and electrical properties in SrTiO3. The specimens were prepared by one-step and two-step sintering with various heating conditions. The microstructure including grain size distributions and grain boundary structures (coincidence-site lattice, CSL) were observed, and the microstructure data were correlated with electrical properties to reveal the importance of grain boundary engineering.

The experimental result of SrTiO3 samples with one-step sintering shows the populations (16-17%) of the CSL grain boundary (Σ3-Σ49) are similar. However, the SrTiO3 samples with Sr/Ti=1.00 have the highest Σ3 frequency (~4%) than that (~2%) of the other SrTiO3 samples (Sr/Ti=0.91 and 1.14). By combining the electrical measurements, the CSL populations cannot be correlated with and the activation energy of grain boundary conductivity because the properties of the CSL grain boundaries may change with the nonstoichiometric conditions (Sr/Ti ratios). In addition, the second phases of TiO2 and Ruddlesden-Popper caused by various Sr/Ti ratios affect the dielectric properties. For the two-step sintering, the similar experimental results were obtained.

[1] J.F. Scott, High-dielectric constant thin films for dynamic random access memories (DRAM), Annual Review of Materials Science 28 (1) (1998) 79-100.
[2] J. Siddiqui, E. Cagin, D. Chen, J.D. Phillips, ZnO thin-film transistors with polycrystalline (Ba,Sr)TiO3 gate insulators, Applied Physics Letters 88 (21) (2006) 212903-212903.
[3] K. Ueno, W. Sakamoto, T. Yogo, S.-i. Hirano, Processing of novel strontium titanate-based thin-film varistors by chemical solution deposition, J. Am. Ceram. Soc. 86 (1) (2003) 99-104.
[4] N. Yamoaka, SrTiO3 -based boundary-layer capacitors, Am.Ceram. Soc. Bull. 65 (1986) 1149–1152.
[5] N.Q. Minh, Ceramic fuel cells, J. Am. Ceram. Soc. 76 (3) (1993) 563-588.
[6] K.J. Dudeck, N. Benedek, D.J.H. Cockayne, HREM study of the SrTiO3 Σ3 (112) grain boundary
EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany, in: M. Luysberg, K. Tillmann, T. Weirich (Eds.), Springer Berlin Heidelberg, 2008, pp. 17-18.
[7] S. Hutt, S. Kostlmeier, C. Elsasser, Density functional study of the Σ3 (111) [10] symmetrical tilt grain boundary in SrTiO3, Journal of Physics: Condensed Matter 13 (18) (2001) 3949.
[8] O. Kienzle, M. Exner, F. Ernst, Atomistic structure of Σ = 3, (111) grain boundaries in strontium titanate, physica status solidi (a) 166 (1) (1998) 57-71.
[9] S.B. Lee, W. Sigle, W. Kurtz, M. Ruhle, Temperature dependence of faceting in [Sigma]5(310)[001] grain boundary of SrTiO3, Acta Mater. 51 (4) (2003) 975-981.
[10] R.A. De Souza, J. Fleig, J. Maier, Z. Zhang, W. Sigle, M. Ruhle, Electrical resistance of low-angle tilt grain boundaries in acceptor-doped SrTiO3 as a function of misorientation angle, J. Appl. Phys. 97 (5) (2005) 053502-053507.
[11] A. Tkach, A. Almeida, J.A. Moreira, T.M. Correia, M.R. Chaves, O. Okhay, P.M. Vilarinho, I. Gregora, J. Petzelt, Enhancement of tetragonality and role of strontium vacancies in heterovalent doped SrTiO3, Applied Physics Letters 98 (5) (2011) 052903-052903.
[12] W.D. Kingery, H.K. Bowen, D.R. Uhlmann, R. Frieser, Introduction to ceramics, Journal of The Electrochemical Society 124 (3) (1977) 152C-152C.
[13] A. Okazaki, M. Kawaminami, Lattice constant of strontium titanate at low temperatures, Materials Research Bulletin 8 (5) (1973) 545-550.
[14] N.H. Chan, R.K. Sharma, D.M. Smyth, Nonstoichiometry in SrTiO3, Journal of The Electrochemical Society 128 (8) (1981) 1762-1769.
[15] S. Witek, D.M. Smyth, H. Piclup, Variability of the Sr/Ti ratio in SrTiO3, J. Am. Ceram. Soc. 67 (5) (1984) 372-375.
[16] S.N. Ruddlesden, P. Popper, The compound Sr3Ti2O7 and its structure, Acta Crystallographica 11 (1) (1958) 54-55.
[17] C. Noguera, Theoretical investigation of the Ruddlesden-Popper compounds Srn+1TinO3n+1 (n=1-3), Philosophical Magazine Letters 80 (3) (2000) 173-180.
[18] M. Baurer, D. Weygand, P. Gumbsch, M.J. Hoffmann, Grain growth anomaly in strontium titanate, Scripta Materialia 61 (6) (2009) 584-587.
[19] P. Blennow, K.K. Hansen, L. Reine Wallenberg, M. Mogensen, Effects of Sr/Ti-ratio in SrTiO3-based SOFC anodes investigated by the use of cone-shaped electrodes, Electrochimica Acta 52 (4) (2006) 1651-1661.
[20] A. Tkach, P.M. Vilarinho, A.M.R. Senos, A.L. Kholkin, Effect of nonstoichiometry on the microstructure and dielectric properties of strontium titanate ceramics, Journal of the European Ceramic Society 25 (12) (2005) 2769-2772.
[21] S.E. Dann, M.T. Weller, Structure and oxygen stoichiometry in Sr3Co2O7-y (0.94 <= y <= 1.22), Journal of Solid State Chemistry 115 (2) (1995) 499-507.
[22] C. Navas, H.L. Tuller, H.-C.z. Loye, Electrical conductivity and nonstoichiometry in doped Sr3Ti2O7, Journal of the European Ceramic Society 19 (6-7) (1999) 737-740.
[23] S.-Y. Chung, S.-J.L. Kang, Intergranular amorphous films and dislocations-promoted grain growth in SrTiO3, Acta Mater. 51 (8) (2003) 2345-2354.
[24] S.-Y. Chung, S.-J.L. Kang, Effect of dislocations on grain growth in strontium titanate, J. Am. Ceram. Soc. 83 (11) (2000) 2828-2832.
[25] M. Baurer, H. Kungl, M.J. Hoffmann, Influence of Sr/Ti stoichiometry on the densification behavior of strontium titanate, J. Am. Ceram. Soc. 92 (3) (2009) 601-606.
[26] S. Komornicki, S. Kozinski, B. Mirek, M. Rekas, The influence of stoichiometry on electrical properties of strontium titanate, Solid State Ionics 42 (1-2) (1990) 7-13.
[27] R. Roy, in Phase diagrams for ceramists, edited by E. M. Levin, C. R.
Robbins and H. F. McMurdie (American Ceramic Society, Columbus, Ohio,
1964), p. 119.
[28] M. Paranthaman, A. Aruchamy, G. Aravamudan, G.V.S. Rao, Photoelectrochehical studies on the mixed oxides,SrTiO3,Sr2TiO4 and Sr3Ti2O7, Materials Chemistry and Physics 14 (4) (1986) 349-365.
[29] C.J. Yim, S.U. Kim, Y.S. Kang, M.H. Cho, D.H. Ko, Enhanced electrical properties of SrTiO3 thin films grown by plasma-enhanced atomic layer deposition, Electrochemical and Solid-State Letters 14 (10) (2011) G45-G48.
[30] S.W. Lee, J.H. Han, S. Han, W. Lee, J.H. Jang, M. Seo, S.K. Kim, C. Dussarrat, J. Gatineau, Y.-S. Min, C.S. Hwang, Atomic layer deposition of SrTiO3 thin films with highly enhanced growth rate for ultrahigh density capacitors, Chemistry of Materials 23 (8) (2011) 2227-2236.
[31] C. Dubourdieu, O. Salicio, F. Ducroquet, I. Matko, S. Daniele, High k SrTiO3 perovskite on Si/SiO2: CVD growth, interface engineering and dielectric properties, ECS Meeting Abstracts 901 (19) (2009) 833-833.
[32] E.R. Leite, C.M.G. Sousa, E. Longo, J.A. Varela, Influence of polymerization on the synthesis of SrTiO3: part I. Characteristics of the polymeric precursors and their thermal decomposition, Ceramics International 21 (3) (1995) 143-152.
[33] Y. Wang, G. Xu, L. Yang, Z. Ren, X. Wei, W. Weng, P. Du, G. Shen, G. Han, Formation of single-crystal SrTiO3 dendritic nanostructures via a simple hydrothermal method, Journal of Crystal Growth 311 (8) (2009) 2519-2523.
[34] H. Yu, S. Ouyang, S. Yan, Z. Li, T. Yu, Z. Zou, Sol-gel hydrothermal synthesis of visible-light-driven Cr-doped SrTiO3 for efficient hydrogen production, Journal of Materials Chemistry 21 (30) (2011) 11347-11351.
[35] S. Fuentes, R. Zarate, E. Chavez, P. Munoz, D. Diaz-Droguett, P. Leyton, Preparation of SrTiO3 nanomaterial by a sol–gel-hydrothermal method, Journal of Materials Science 45 (6) (2010) 1448-1452.
[36] H.E. Zorel Jr, L.S. Guinesi, C.A. Ribeiro, M.S. Crespi, SrTiO3 preparation through coprecipitation methods, Materials Letters 42 (1–2) (2000) 16-20.
[37] M. Baurer, et al., Changes in macroscopic behaviour through segregation in niobium doped strontium titanate, Journal of Physics: Conference Series 94 (1) (2008) 012015.
[38] J.C.C. Abrantes, A. Feighery, A.A.L. Ferreira, J.A. Labrincha, J.R. Frade, Impedance spectroscopy study of niobium-doped strontium titanate ceramics, J. Am. Ceram. Soc. 85 (11) (2002) 2745-2752.
[39] 金山, 鈦酸鍶陶瓷材料制備方法的進展, 鹽湖研究 12 (3) (2004).
[40] J.P. Coutures, P. Odier, C. Proust, Barium titanate formation by organic resins formed with mixed citrate, Journal of Materials Science 27 (7) (1992) 1849-1856.
[41] 劉冠芳, 鈦酸鍶陶瓷燒結的研究進展, 絕緣材料 42 (3) (2009).
[42] Lehockey EM, Limoges D, Palumbo G, Sklarchuk J, Tomantschger K, Vinczc A. J Power Sources 1999;78:79.
[43] G. Hasson, Herbeuva.I, J. Y. Boos, et al., Surface Science 31, 115 (1972).
[44] D. Wolf, Journal of Applied Physics 69, 185 (1991)
[45] V. Randle, Overview No. 127 The role of the grain boundary plane in cubic polycrystals, Acta Mater. 46 (5) (1998) 1459-1480.
[46] H.-K. Kim, W.-S. Ko, H.-J. Lee, S.G. Kim, B.-J. Lee, An identification scheme of grain boundaries and construction of a grain boundary energy database, Scripta Materialia 64 (12) (2011) 1152-1155.
[47] A. Subramaniam, C.T. Koch, R.M. Cannon, M. Ruhle, Intergranular glassy films: An overview, Materials Science and Engineering: A 422 (1-2) (2006) 3-18.
[48] V. Randle, Twinning-related grain boundary engineering, Acta Mater. 52 (14) (2004) 4067-4081.
[49] M. L. Kronberg and F. H. Wilson, Transactions of the American Institute of
Mining and Metallurgical Engineers 185, 501 (1949).
[50] G. Palumbo and K. T. Aust, Acta Metallurgica et Materialia 38, 2343 (1990).
[51] G. Palumbo, K.T. Aust, U. Erb, P.J. King, A.M. Brennenstuhl, P.C. Lichtenberger, On annealing twins and CSL distributions in F.C.C. polycrystals, physica status solidi (a) 131 (2) (1992) 425-428.
[52] G. Dimou and K. T. Aust, Acta Metallurgica 22, 27 (1974)
[53] D. C. Hinz and J. A. Szpunar, Physical Review B 52, 9900 (1995).
[54] G. Palumbo and K. T. Aust, Canadian Metallurgical Quarterly 34, 165 (1995).
[55] V. M. Kosevich, V. N. Klimenko, A. N. Gladkikh, et al., Interface Science 3, 151 (1995).
[56] N. Rajmohan, J. A. Szpunar, and Y. Hayakawa, Acta Materialia 47, 2999 (1999).
[57] S.B. Lee, W. Sigle, M. Ruhle, Faceting behavior of an asymmetric SrTiO3 [Sigma]5 [001] tilt grain boundary close to its defaceting transition, Acta Mater. 51 (15) (2003) 4583-4588.
[58] F. Ernst, O. Kienzle, M. Ruhle, Structure and composition of grain boundaries in ceramics, Journal of the European Ceramic Society 19 (6-7) (1999) 665-673.
[59] F. Ernst, M.L. Mulvihill, O. Kienzle, M. Ruhle, Preferred grain orientation relationships in sintered perovskite ceramics, J. Am. Ceram. Soc. 84 (8) (2001) 1885-1890.
[60] D.M. Saylor, B. El Dasher, T. Sano, G.S. Rohrer, Distribution of grain boundaries in SrTiO3 as a function of five macroscopic parameters, J. Am. Ceram. Soc. 87 (4) (2004) 670-676.
[61] M.-B. Park, S.-J. Shih, D.J.H. Cockayne, The preferred CSL misorientation distribution in polycrystalline SrTiO3, Journal of Microscopy 227 (3) (2007) 292-297.
[62] K. Hayashi, T. Yamamoto, Y. Ikuhara, T. Sakuma, Formation of potential barrier related to grain-boundary character in semiconducting barium titanate, J. Am. Ceram. Soc. 83 (11) (2000) 2684-2688.
[63] F. Horikiri, L.Q. Han, A. Kaimai, T. Otake, K. Yashiro, T. Kawada, J. Mizusaki, The influence of grain boundary on the conductivity of donor doped SrTiO3, Solid State Ionics 177 (26-32) (2006) 2555-2559.
[64] K. Bodišova, P. Šajgalik, D. Galusek, P. Švančarek, Two-stage sintering of alumina with submicrometer grain size, J. Am. Ceram. Soc. 90 (1) (2007) 330-332.
[65] F.J.T. Lin, L.C. de Jonghe, M.N. Rahaman, Microstructure refinement of sintered alumina by a two-step sintering technique, J. Am. Ceram. Soc. 80 (9) (1997) 2269-2277.
[66] K. Maca, V. Pouchly, P. Zalud, Two-step sintering of oxide ceramics with various crystal structures, Journal of the European Ceramic Society 30 (2) (2010) 583-589.
[67] M. Mazaheri, A.M. Zahedi, S.K. Sadrnezhaad, Two-step sintering of nanocrystalline ZnO compacts: effect of temperature on densification and grain growth, J. Am. Ceram. Soc. 91 (1) (2008) 56-63.
[68] X.H. Wang, X.Y. Deng, H.-L. Bai, H. Zhou, W.-G. Qu, L.T. Li, I.W. Chen, Two-step sintering of ceramics with constant grain-size, II: BaTiO3 and Ni–Cu–Zn ferrite, J. Am. Ceram. Soc. 89 (2) (2006) 438-443.
[69] I.W. Chen, X.H. Wang, Sintering dense nanocrystalline ceramics without final-stage grain growth, Nature 404 (6774) (2000) 168-171.
[70] C. Herring, ‘‘Effect of Change of Scale on Sintering Phenomena,’’ J. Appl. Phys., 21 [4] 301–3 (1950).
[71] J.D. Hansen, R.P. Rusin, M.-H. Teng, D.L. Johnson, Combined-stage sintering model, J. Am. Ceram. Soc. 75 (5) (1992) 1129-1135.
[72] J. Zhao, M.P. Harmer, Sintering kinetics for a model final-stage microstructure: A study of AI2O3, Philosophical Magazine Letters 63 (1) (1991) 7-14.
[73] K. Maca, V. Pouchly, Z. Shen, Two-step sintering and spark plasma sintering of Al2O3, ZrO2 and SrTiO3 ceramics, Integrated Ferroelectrics: An International Journal 99 (1) (2008) 114 - 124.
[74] P. Balaya, M. Ahrens, L. Kienle, J. Maier, B. Rahmati, S.B. Lee, W. Sigle, A. Pashkin, C. Kuntscher, M. Dressel, Synthesis and characterization of nanocrystalline SrTiO3, J. Am. Ceram. Soc. 89 (9) (Azx c/<>N32C) 2804-2811.
[75] Y.-I. Lee, Y.-W. Kim, M. Mitomo, Effect of processing on densification of nanostructured SiC ceramics fabricated by two-step sintering, Journal of Materials Science 39 (11) (2004) 3801-3803.
[76] M. Mazaheri, A. Simchi, F. Golestani-Fard, Densification and grain growth of nanocrystalline 3Y-TZP during two-step sintering, Journal of the European Ceramic Society 28 (15) (2008) 2933-2939.
[77] 黃. 林麗娟, FE-SEM/CL/EBSD 分析技術簡介, 工業材料雜誌 201 期 (2003).
[78] A.J. Schwartz, M. Kumar, and B.L. Adams, Electron Backscatter Diffraction in Materials Science, Kluwer Academic, New York, 2000.

[79] Electron Microscopy and Analysis, Third Edition By Peter J. Goodhew, John Humphreys, Richard Beanland Published 29th November 2000 by Taylor & Francis
[80] http://www.oxford-instruments.com/
[81] E. Barsoukov and J. R. Macdonald, "Impedance Spectroscopy, Theory Experiment and Applications," John Wiley & Sons. Inc.,
(2005).
[82] E.B.a.J.R. Macdonald, Impedance spectroscopy, theory experiment and applications, Second Edition ed., John Wiley & Sons, Inc., Hoboken, New Jersey., 2005.
[83] J. Fleig, J. Maier, A finite element study on the grain boundary impedance of different microstructures, Journal of The Electrochemical Society 145 (6) (1998) 2081-2089.
[84] I. Arvanitidis, D. Sichen, S. Seetharaman, H. Sohn, The intrinsic thermal decomposition kinetics of SrCO3 by a nonisothermal technique, Metallurgical and Materials Transactions B 28 (6) (1997) 1063-1068.
[85] S. Šturm, A. Rečnik, C. Scheu, M. Čeh, Formation of Ruddlesden–Popper faults and polytype phases in SrO-doped SrTiO3, J. Mater. Res. 15 (10) (2000) 2131-2139.
[86] G. Rohrer, Grain boundary energy anisotropy: a review, Journal of Materials Science 46 (18) (2011) 5881-5895.
[87] H. Shen, Y. Song, H. Gu, P. Wang, Y. Xi, A high-permittivity SrTiO3-based grain boundary barrier layer capacitor material single-fired under low temperature, Materials Letters 56 (5) (2002) 802-805.
[88] X.-T. Su, Q.-Z. Yan, X.-H. Ma, W.-F. Zhang, C.-C. Ge, Effect of co-dopant addition on the properties of yttrium and neodymium doped barium cerate electrolyte, Solid State Ionics 177 (11–12) (2006) 1041-1045.
[89] J.-x. Wang, W.-h. Su, D.-p. Xu, T.-m. He, Electrical properties of solid solutions Ba1.1Ce1−xEuxO3−δ, J. Alloy. Compd. 421 (1–2) (2006) 45-48.
[90] A.K. Azad, J.T.S. Irvine, Synthesis, chemical stability and proton conductivity of the perovksites Ba(Ce,Zr)1−xScxO3−δ, Solid State Ionics 178 (7–10) (2007) 635-640.
[91] S.D. Flint, R.C.T. Slade, Variations in ionic conductivity of calcium-doped barium cerate ceramic electrolytes in different atmospheres, Solid State Ionics 97 (1–4) (1997) 457-464.
[92] Takuya HOSHINA, Kayo TAKIZAWA,, Domain size effect on dielectric properties of barium titanate ceramics, Japanese Journal of Applied Physics, 2000.