Available online at www.sciencedirect.com Materials Chemistry and Physics 109 (2008) 39–44 Studies on structural, morphological and electrical properties of Ce 1-x Gd x O 2-(x/2) M.G. Chourashiya, J.Y. Patil, S.H. Pawar, L.D. Jadhav ∗ Department of Physics, Shivaji University, Vidyanagar, Maharashtra, Kolhapur 416004, India Received 27 June 2007; received in revised form 26 October 2007; accepted 28 October 2007 Abstract The gadolinium-doped ceria (GDC) is considered as one of the most promising electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs). Since the operating temperature of SOFC mainly depends on properties of electrolytes, the structural, morphological and electrical properties of GDC are studied as a function of concentration of ‘Gd’ and sintering temperature. The lattice parameter, density, surface morphology and conductivity of GDC samples are improved upon sintering. Further an increase in lattice parameter with concentration of Gd confirms the dissolution of Gd 2 O 3 in CeO 2 . The crystallite size and grain size was observed to decrease with “Gd” concentration. All GDC samples sintered at 1773 K showed uniform and smoother surfaces with conductivity ∼0.1 S cm -1 at 1023 K and activation energies less than 0.9 eV. An impedance study confirms the formation of well-grown grains at higher sintering temperature. © 2007 Elsevier B.V. All rights reserved. Keywords: Oxides; Sintering; Electron microscopy; Electrical conductivity 1. Introduction Intermediate temperature solid oxide fuel cells (IT-SOFCs) have been of immense interest because they offer many advantages over high temperature SOFCs (HT-SOFCs), which includes smaller thermal mismatch between its components, rapid startup with less energy consumption, etc. The doped ceria with high ionic conductivity at relatively low temperature is considered to be a strong candidate for use as an electrolyte in SOFCs in addition to its applications in oxygen sensors, oxy- gen separation, etc. [1,2]. Ceria have been doped with variety of cations. However, the host lattices of ceria are more compatible with trivalent cations and the stable structure is obtained for the ratio between cations and the anions radii close to 0.70 [3]. The ceria is, therefore, either doped with gadolinium or samarium [4]. Different processing and synthesis methods have been adop- ted to prepare doped ceria with desired properties [5–8]. Solid-state reaction, a simple and cost-effective method, is often adopted to prepare polycrystalline bulk electrolyte samples [9,10]. It was observed that the electrical properties of polycrys- ∗ Corresponding author. Tel.: +91 9890694409; fax: +91 231 2691533/2333. E-mail address: ldjadhav.phy@gmail.com (L.D. Jadhav). talline electrolytes depend not only on the chemical composition of the material but also to a large extent on various microstructu- ral parameters, e.g. porosity [11,12], and the thermal treatment during processing of a particular specimen [13]. Ceramic route on one hand enables easy stoichiometric doping while on other, the samples prepared are in general porous. However, the poro- sity and uniformity of samples can be improved using proper thermal treatments. The gadolinium-doped ceria (GDC) is one of the most pro- mising electrolytes to be operated below 900 K [14]. Hence in the present work, GDC is prepared with different doping concentrations of gadolinium. Sintering of this oxide is a crucial parameter affecting the density, porosity and the other properties. Therefore, the effect of sintering temperature on the structural, morphological and electrical properties of GDC doped with dif- ferent doping concentrations was studied and discussed. The ac impedance spectra were measured and employed to illustrate the effect of dopant concentration and the sintering temperature. 2. Experimental 2.1. Sample preparation Polycrystalline gadolinium-doped ceria were prepared with different pro- cessing parameters. Commercially available powders of CeO 2 and Gd 2 O 3 (AR 0254-0584/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2007.10.028