本研究是利用固態反應法合成鈮摻雜鍺酸鑭基電解質材料，藉由不同添加量之 Nb5+ 取代 La9.5Ge6-xNbxO26.25+y 中的 Ge4+ 位置 (x = 0，0.1，0.15，0.2，0.25，0.5，0.75，1)，觀察其晶體結構與導電性質之關聯性。
實驗結果顯示隨著鈮添加量的增加，於 x = 0.5 便出現二次相，已超出固溶範圍。針對煅燒粉末以 Rietveld 方法模擬精算晶格常數，得到固溶極限內之鍺氧四面體體積會因為鈮的摻雜而增加，進而影響整體晶體結構。而鈮的摻雜會使燒結緻密之溫度提高，且觀察到高溫下之 La9.5Ge6O26.25 會因為鍺揮發產生二次相 (GeO2)，當 x ≥ 0.5 之燒結體隨著溫度升高亦會生成較多二次相 (LaNbO4 和 La3NbO7)。
以 1350℃/3 h 作為燒結條件之試片，在 x = 0.2 時具有最佳導電率 (0.0248 S/cm)，推測此比例之鈮摻雜造成晶格扭曲撐開程度較大，使得間隙式氧離子可以輕易通過；當 x = 0.75 時含有較多二次相則會使導電率下降，且活化能在二次相生成後隨之變高。

A series of Niobium doped Lanthanum-Germanate apatite-type material, La9.5Ge6-xNbxO26.25+y (x = 0，0.1，0.15，0.2，0.25，0.5，0.75，1), have been prepared by solid-state synthesis. The result shows that, since Nb5+ ion has larger ionic radii than Ge4+ ion, crystal structure has been distort which makes interstitial oxygen can be migrated easily. On contrary, the conductivity decreases with second phase presented.
The purpose of this paper is to study the relationship between crystal structure and conductivity. All La/Ge based powders have been calcined by 1100℃ for 3 hours and have been determined from X-ray powder diffraction data which uses Rietveld method. Then these specimens are sintered at 1350℃/3 h for measurement of conductivity. Second phase forms when Nb5+ dosage ≥ 0.5. The volume of Ge/Nb－O tetrahedron increases by Nb5+ doped. La9.5Ge5.8Nb0.2O26.35 has the highest conductivity (0.0248 S/cm) of this series at 800℃, and the conductivity of La9.5Ge5.25Nb0.75O26.625 decreases to 0.0075 S/cm.

[1] S. Nakayama, H. Aono and Y. Sadaoka (1995), “Ionic conductivity of Ln10(SiO4)6O3 (Ln = La, Nd, Sm, Gd and Dy),” Chemistry Letters, 24, pp. 431~432.
[2] S. Nakayama, T. Kageyama, H. Aono and Y. Sadaoka (1995), “Ionic conductivity of lanthanoid silicates Ln10(SiO4)6O3 (Ln = La, Nd, Sm, Gd, Dy, Y, Ho, Er and Yb),” Journal of Materials Chemistry, 5, pp. 1801~1805.
[3] L. León-Reina, E.R. Losilla, M. Martínez-Lara, M.C. Martín-Sedeño, S. Bruque, P.Núñez, D. V. Sheptyakov and M. A. G. Aranda, (2005), “High oxide ion conductivity in Al-doped germanium oxyapatite, ” Chemistry of Materials, 17 (3), pp. 596~600.
[4] 林婉茹、徐永富、王錫福 (2012)，「摻雜對磷灰石結構鍺酸鑭基電解質應用於固態氧化物燃料電池之特性影響研究」，國立台北科技大學材料工程與科學研究所碩士論文。
[5] 發行人葉惠青 (2010)，2010能源產業技術白皮書，台北：經濟部能源局，第 341 頁。
[6] http://www.rz.uni-karlsruhe.de/~cf01/research/research_SOFC.html
[7] http://www.fuelcelltoday.com/about-fuel-cells/technologies/sofc
[8] http://ssrl.slac.stanford.edu/research/highlights_archive/rockyflats.html
[9] Federico Gallino , Cristiana Di Valentin and Gianfranco Pacchioni (2011), “Band gap engineering of bulk ZrO2 by Ti doping,” Phys. Chem. Chem. Phys., 13, pp. 17667~17675.
[10] http://www.doitpoms.ac.uk/tlplib/fuel-cells/printall.php
[11] Junjiang Zhu and Arne Thomas (2009), “Perovskite-type mixed oxides as catalytic material for NO removal,” Applied Catalysis B: Environmental, 92 (3–4), pp. 225~233.
[12] S. Nakayama, Y. Higuchi, Y. Kondo, and M. Sakamoto (2004), “Effects of cation- or oxide ion-defect on conductivities of apatite-type La–Ge–O system ceramics,” Solid State Ionics, 170, pp. 219~223.
[13] P.R. Slater, J.E.H. Sansom, and J.R. Tolchard (2005), “Development of Apatite-Type Oxide Ion Conductors,” Chemistry Record, 4 (3), pp. 373~384.
[14] S. Nakayama and M. Sakamoto (1998), “Electrical properties of new type high oxide ionic conductor RE10Si6O27 (RE = La, Pr, Nd, Sm, Gd, Dy), ” Journal of the European ceramic Society, 18, pp. 1413~1418.
[15] H. Yoshioka (2007), “Enhancement of ionic conductivity of apatite-type lanthanum silicates doped with cations,” Journal of the American Ceramic Society, 90, pp. 3099~3105.
[16] S. Nakayama, M. Sakamoto, M. Higuchi, K. Kodaira, M. Sato, S. Kakita, T. Suzuki, and K. Itoh (1999), "Oxide ionic conductivity of apatite type Nd9.33(SiO4)6O2 single crystal,” Journal of the European Ceramic Society, 19, pp. 507~510.
[17] L. Leon-Reina, J. Manuel Porras-Vazquez, Enrique R. Losilla, and Miquel A. G. Aranda (2006), “Interstitial oxide positions in oxygen-excess oxyapatites,” Solid State Ionics, 177, pp. 1307~1315.
[18] S. Nakayama and M. Sakamoto (2001), “Ionic conductivities of apatite-type Lax(GeO4)6O1.5x-12 (x=8-9.33) polycrystals,” Journal of Materials Science Letters, 20, pp. 1627~1629.
[19] J.E.H. Sansom, L. Hildebrandt, and P.R. Slater (2002), “An Investigation of the Synthesis and Conductivities of La-Ge-O Based Systems,” lonics, 8, pp. 155~160.
[20] A. Orera, T. B aikie, P. Panchmatia, T. J. White, J. Hanna, M. E. Smith, M. S. Islam, E.Kendrick, and P. R. Slater (2011), “Strategies for the Optimisation of the Oxide Ion Conductivities of Apatite-Type Germanates,” Full Cells, 11, pp. 10~16.