Díaz Guillén, M. R.Moreno, K. J.Díaz Guillén, J. A.Fuentes, A .F.Naval, K. L. NgaiGarcia Barriocanal, JavierSantamaría Sánchez-Barriga, JacoboLeón Yebra, Carlos2023-06-202023-06-202008-091) A. P. Ramírez, A. Hayashi, R. J. Cava, R. Siddharthan, B. S. Shastry, Nature London, 399, 333, 1999. 2) J. Snyder, J. S. Slusky, R. J. Cava, P. Schiffer, Nature London, 413, 48, 2001. 3) W. J. Weber, R. C. Ewing, Science, 289, 2051, 2000. 4) O. Porat, C. Heremans, H. L. Tuller, Solid State Ionics, 94, 75, 1997. 5) E. V. Tsipis, V. V. Kharton, J. R. Frade, J. Eur. Ceram. Soc., 25, 2623, 2005. 6) S. A. Kramer, H. L. Tuller, Solid State Ionics, 82, 15, 1995. 7) M. A. Subramanian, G. Aravamudan, G. V. Subba Rao, Prog. Solid State Chem., 15, 55, 1983. 8) M. Pirzada, R. W. Grimes, L. Minervini, J. F. Maguire, K. E. Sickafus, Solid State Ionics, 140, 201, 2001. 9) P. J. Wilde, C. R. A. Catlow, Solid State Ionics, 112, 185, 1998. 10) R. E. Williford, W. J. Weber, R. Devanathan, J. D. Gale, J. Electroceram., 3, 409, 1999. 11) P. J. Wilde, C. R. A. Catlow, Solid State Ionics, 112, 173, 1998. 12) K. J. Moreno, G. Mendoza-Suárez, A. F. Fuentes, J. García Barriocanal, C. León, J. Santamaría, Phys. Rev. B, 71, 132301, 2005. 13) K. J. Moreno, R. Silva-Rodrigo, A. F. Fuentes, J. Alloys Compd., 390, 230, 2005. 14) K. J. Moreno, M. A. Guevara-Liceaga, A. F. Fuentes, J. García Barriocanal, C. León, J. Santamaría, J. Solid State Chem., 179, 928, 2006. 15) A. F. Fuentes, K. Boulahya, M. Maczka, J. Hanuza, U. Amador, Solid State Sci., 7, 343, 2005. 16) N. Kim, C. P. Grey, J. Solid State Chem., 175, 110, 2003. 17) M. P. van Dijk, F. C. Mijlhoff, A. J. Burggraaf, J. Solid State Chem., 62, 377, 1986. 18) C. Heremans, B. J. Wuensch, J. K. Stalick, E. Prince, J. Solid State Chem., 117, 108, 1995. 19) A. K. Jonscher, Dielectric Relaxation in Solids (Chelsea Dielectric, London), 1983. 20) K. L. Ngai, R. W. Rendell, ACS Symp. Ser., 679, 45, 1997. 21) K. L. Ngai, C. León, Phys. Rev. B, 60, 9396, 1999. 22) C. T. Moynihan, Solid State Ionics, 105, 175, 1998. 23) K. Funke, R. D. Banhatti, S. Bruckner, C. Cramer, D. Wilmer, Solid State Ionics, 154-155, 65, 2002 --- K. Funke, R. D. Banhatti, J. Non-Cryst. Solids, 353, 3845, 2007. 24) K. L. Ngai, Phys. Rev. B, 48, 13481, 1993. 25) R. D. Shannon, Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr., 32, 751, 1976. 26) P. K. Moon, H. L. Tuller, Solid State Ionics, MRS Symposia Proceedings No. 135 (Materials Research Society, Pittsburgh), 1989, p. 149. 27) H. Yamamura, H. Nishino, K. Kakinuma, K. Nomura, Solid State Ionics, 158, 359, 2003. 28) T. Van Dijk, K. J. de Vries, A. J. Burggraaf, Phys. Status Solidi A, 58, 115, 1980.1098-012110.1103/PhysRevB.78.104304https://hdl.handle.net/20.500.14352/51401© 2008 The American Physical Society. This work has been carried out with the financial support of Mexican Conacyt Grant No. SEP-2003-C02-44075 and Spanish MCYT Contracts No. MAT2005-06024-C02 and No. MAT2008-06517-C02. M.R.D.G. thanks Conacyt for financial support. K.L. Ngai was supported in part by ONR under Program Element and Project 61153N.In this work we evaluate the effect of cation size on the dc activation energy needed for oxygen ion migration, E_(dc), in highly disordered pyrochlore-type ionic conductors A_(2)B_(2)O_(7). Twenty six compositions with the general formula, Ln_(2)Zr_(2−y)Ti_(y)O_(7), Ln_(1.7)Mg_(0.3)Zr_(2)O_(7) (Ln=Y, Dy, and Gd), and Gd_(2−y)La_(y)Zr_(2)O_(7), were prepared by mechanical milling, and their electrical properties were measured by using impedance spectroscopy as a function of frequency and temperature. By using the coupling model we also examine the effect of cation radii R_(A) and R_(B) on the microscopic potential-energy barrier, E_(a), which oxygen ions encounter when hopping into neighboring vacant sites. We find that, for a fixed B-site-cation radius R_(B), both activation energies decrease with increasing A-site-cation size, R_(A), as a consequence of the increase in the unit-cell volume. In contrast, for a given R_(A) size, the E_(dc) of the Ln_(2)Zr_(2−y)Ti_(y)O_(7) series increases when the average R_(B) size increases. This behavior is associated with enhanced interactions among mobile oxygen ions as the structural disorder increases with R_(B).engjournal articlehttp://dx.doi.org/10.1103/PhysRevB.78.104304http://journals.aps.org/open access537Electrical relaxationConstituent oxidesCoupling modelSpin iceConductivityMigrationDiffusionGd_(2)Ti_(2)O_(7)GlassesMelts.ElectricidadElectrónica (Física)2202.03 Electricidad