JOURNAL OF RARE EARTHS, Vol. 28, No. 3, Jun. 2010, p. 435 Corresponding author: S. Selvasekarapandian (E-mail: sekarapandian@rediffmail.com) DOI: 10.1016/S1002-0721(09)60128-9 Conductivity and dielectric studies on LiCeO 2 M. Prabu 1,2 , S. Selvasekarapandian 2 , A.R. Kulkarni 1 , G. Hirankumar 2 , C. Sanjeeviraja 3 (1. Department of Metallurgical Engineering and Material Science, Indian Institute of Technology Bombay, Mumbai, India; 2. Department of Physics, Kalasalingam Uni- versity, Krishnankoil-626 190, Tamilnadu, India; 3. Department of Physics, Alagappa University, Karaikudi-630 003, Tamilnadu, India) Received 15 March 2010; revised 19 April 2010 Abstract: LiCeO 2 was prepared by a solid-state reaction method using microwave heat treatment and identified by X-ray diffractometry. Li- CeO 2 has monoclinic crystal structure whose conductivity and dielectric properties were studied over a range of frequency (42 Hz to 1 MHz) and temperatures (30–500 °C) using ac technique of complex impedance analyzer HIOKI 3532. Combined impedance and modulus plots were used as tools to analyze the sample behaviour as a function of frequency at different temperatures. The d.c. conductivity (ı dc ) followed the Arrhenius relation. The modulus analysis and dielectrics studies showed the non-Debye dielectric relaxation nature. Keywords: lithium-ion batteries; impedance; conductivity; dielectric analysis; complex modulus; rare earths During the past decade, a number of efforts were made by researchers towards the development of high performance rechargeable Li-ion batteries with high specific capacity, long cycleability and calendar life [1–7] . Nowadays with the discovery of layered rare earth oxides and their related prop- erties in energy storage devices, there has been a large amount of research work in search of new materials for in- dustrial applications. Layered rare earth oxides including lithium as mobile cation are of interest in the field of solid state batteries [8] . These materials have application in high-temperature lithium batteries. Vores reported the syn- thesis of lithium doped rare earth oxides with ABO 2 -type structure [9] . The electrical characterization of LiDyO 2 has al- ready been studied by Selvasekarapandian and Vijayaku- mar [10] . Continuation of that work, synthesis and impedance studies of lithium cerium oxide (LiCeO 2 ) were presented and discussed. 1 Experimental The LiCeO 2 was prepared by solid-state reaction method. High-purity raw materials (Li 2 CO 3 , CeO 2 ) were weighed and taken in the appropriate stoichiometric ratio. The physical mixture of these raw materials was then mixed mechanically in a mortar and pestle. Solid state reaction was carried out in a microwave furnace at 800 °C for 1 h. The melted sample was cooled slowly and was crushed into fine powders and sprayed in a die. A pressure around 4000 kg/cm 2 was applied to form a pellet with 0.1 cm thickness and 1.0 cm diameter. The pellet was sintered at 600 °C for 6 h, followed by slow cooling process at air atmosphere. The pellet was finally pol- ished to make their faces smooth and parallel. The X-ray diffraction (XRD) analysis was done using an XPERT-PRO X-ray diffractometer PW3050/60 with Cu KĮ radiation. An impedance analyzer HIOKI 3532 controlled by a computer was used to obtain the electrical measurements in the range of 42 Hz to 1 MHz over the temperature range of 30–500 °C with silver as an electrode. 2 Results and discussion 2.1 Structure analysis The formation of LiCeO 2 was confirmed using XRD stud- ies. The XRD pattern of LiCeO 2 at room temperature is shown in Fig. 1. The existence of well defined and highly intense peaks confirms the presence of crystalline nature of LiCeO 2 and phase pure products of desired category. The miller indices (hkl ) of all the peaks corresponding to those of LiCeO 2 are indexed as per the JCPDS file number (29-0801). From search match analysis, it is deduced that the compounds possess monoclinic structure with P 21/c space group. 2.2 Impedance spectrum analysis Fig. 2 shows complex impedance spectrum (Cole-Cole Fig. 1 X-ray diffraction pattern of LiCeO 2 at room temperature