CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 9285–9292 Electrical properties of multidoped ceria M. Stojmenović a,n , S. Bošković a , M. Žunić b,c , J.A. Varela c , M. Prekajski a , B. Matović a , S. Mentus d,e a Institute of Nuclear Sciences “Vinča”, Mihajla Petrovića – Alasa 12-14, 11001 Belgrade, University of Belgrade, Serbia b Institute for Multidisciplinary Research, Kneza Višeslava 1, 11030 Belgrade, University of Belgrade, Serbia c Instituto de Quimica, UNESP-LIEC, CMDMC, Rua Prof. Francisco Degni, 55, CEP 14800-900 Araraquara, SP, Brazil d Faculty of Physical Chemistry, Studenski trg 12-16, 11158 Belgrade, University of Belgrade, Serbia e Serbian Academy of Sciences and Arts, Knez Mihajlova 35, 11000 Belgrade, Serbia Received 30 December 2013; received in revised form 28 January 2014; accepted 30 January 2014 Available online 8 February 2014 Abstract Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). As the dopants to CeO 2 , trivalent rare earth oxides such as Nd 2 O 3 , Sm 2 O 3 , Gd 2 O 3 , Dy 2 O 3 and Y 2 O 3 were used, with the total molar fraction of 20%. The pressed powder pellets were subjected to the densification by sintering at 1500 1C, in an air atmosphere. A single-phase crystalline form was evidenced by X-ray diffractometry for both sintered materials. By means of complex impedance measurements, the conductivity of the sintered samples was determined as a function of temperature. At 700 1C, the conductivity amounted to 2.19  10 2 and 1.40  10 2 Ω 1 cm 1 for the SPRT and for the MGNP sample, respectively. The corresponding values of activation energies of conductivity amounted to 0.72 (MGNP) and 0.59 (SPRT) eV in the temperature range 550–700 1C. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Sintering; C. Ionic conductivity; D. CeO 2 ; E. Fuel cells 1. Introduction Owing to its fluorite structure and valuable capabilities, the nanopowders of cerium (IV) oxide (CeO 2 ) doped by trivalent rare earth ions such as Nd 3 þ , Sm 3 þ , Gd 3 þ , Dy 3 þ ,Y 3 þ and Yb 3 þ became a very interesting ceramic electrolytes for solid fuel cells (SOFC—solid oxide fuel cells) [1–4] . These powders displayed an enhanced ionic conductivity thanks to a high concentration of oxygen vacancies [5]. The number of trivalent rare earth ions, introduced into crystal lattice of CeO 2 by partial replacement of Ce 4 þ ions, is practically equal half the number of oxygen vacancies [6, 7]. In previous studies, the oxides of rare earth elements such as La [5, 8–10], Sm [5, 9–15], Gd [16–19], Dy [20, 21] and Yb [22] , and Y [23–25] were used as the dopants most frequently, thanks to a good solubility in ceria. In addition to the number of lattice vacancies, some other factors have been found to influence the conductivity of ceria-based solid electrolytes. The lattice distortion, caused by the difference in ionic radii of Ce 4 þ and dopant ions was found to be one of the factors [26, 27] . The reduction of mean particle diameter and the uni fication of particle dimensions improved the conductivity of nanocrystalline materials [28] . Further to this, the reduction of mean particle diameter may accelerate sintering, and thus help to save energy in the production of electrolytes for fuel cells. The requirements for SOFC characteristics such as high ef ficiency, low operating temperature, and low cost production process for obtaining pollutant-free ceramics, brought doped CeO 2 into a focus of interest of scienti fic community. In our previous study [29] two different methods were used to synthesize the doped CeO 2 nanopowders (where the number of dopants varied from 1 to 6). The relative fraction of each of dopant varied, however, their total molar percent was kept constant at a level of 20% ( x ¼ 0.2), since, according to the previous literature reports, the concentration of dopants of 10–20 mol% enabled the highest ionic conductivities [27, 30] . The physicochemical characteristics of the samples synthesized by two ways were analyzed in a comparative manner. The difference in either synthesis procedure www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2014.01.151 0272-8842 & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author at: INN Vinca, Lab. 170, P. O. Box 522, 11001 Belgrade, Serbia. Tel.: þ 381 11 340 8860; fax: þ 381 11 340 8224. E-mail address: mpusevac@vinca.rs (M. Stojmenović).