Structural and dielectric properties of La 0.8 Te 0.2 MnO 3 Shahid Husain a,n , Irshad Bhat a , Wasi Khan b , Lila Al-Khataby a a Department of Physics, Aligarh Muslim University, Aligarh 202002, India b Department of Applied Physics, Z.H. College of Engg. & Tech., Aligarh Muslim University, Aligarh 202002, India article info Article history: Received 8 October 2012 Received in revised form 21 December 2012 Accepted 23 December 2012 by F. Peeters Available online 31 December 2012 Keywords: A. Manganites C. X-ray diffraction D. Colossal dielectric constant (CDC) D. Universal dielectric response (UDR) abstract We have studied the structural and dielectric properties of La 0.8 Te 0.2 MnO 3 pervoskite compound, has a rhombohedral structure with space group R-3c, at room temperature. Infrared spectrum shows two active bands located at 611 and 410 cm 1 , which can be ascribed to the internal stretching and bending phonon modes. The additional bands observed at 925, 969 and 1383 cm 1 are attributed to the multiphonon scattering. The dielectric constant e 0 shows a step like relaxation behaviour and has been discussed with in the frame work of the Kramers–Kronig transformation model. The ac conductivity follows a universal dielectric response (UDR), and the results were discussed and fitted with the Jump relaxation model (JRM). The occurrence of giant or colossal dielectric constant is most likely due to electrode polarization or interface polarization effect. The depletion layers are arising due to the formation of Schottky barriers at the metallic contacts of semiconducting samples, which may be formed by grain boundaries, can give rise to Maxwell–Wagner type relaxation and apparently very high dielectric constants. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Mixed-valence manganites have been the focus of intense scientific activity over the past several years as they exhibit variety of physical phenomena. These materials are potential candidate for utilization in magnetic sensing and spin polarized transport applications. Their physical properties are governed by the delicate interplay among charge, lattice, orbital and spin degrees of freedom [1–3]. The most prominent feature of doped manganites is the display of colossal magnetoresistance (CMR). Even though the origin of CMR is the subject of investigation due to conflicting reports [4–6]. The manganites also show ferroelectric behaviour [7]. Hence large values of the dielectric constants are expected to be associated with these materials. Recently, materials exhibiting a colossal dielectric constant (CDC) (e 0 410 3 ) have gained considerable attention, due to its applica- tion in random access memories. Fundamental interest was initiated by the observation of CDC behaviour in some high T c compounds [8,9]. During the last decade similar observations of CDC behaviour have been reported in an increasing number of materials, such as transition-metal oxides [10–12]. In various reports [11,12] giant values of the dielectric constant were claimed to persist over broad temperature ranges, showing a step like decreasing behaviour towards higher frequencies. The electron doped manganites are lesser studied materials as compared to hole doped manganites and we have not found many reports on dielectric properties of these materials. In view of this we have selected the Te doped LaMnO 3 , an electron doped manganite and studied its structural and dielectric properties in particular. 2. Experimental The sample La 0.8 Te 0.2 MnO 3 is prepared using the standard solid state reaction route. Stoichiometric amounts of La 2 O 3 , TeO 2 and MnO 2 were mixed ground and pre-sintered at 1273 K for 20 h. The pre-sintered material was again ground and sintered at 1373 K, with two intermediate grindings. Finally, the material was pressed into a disc shaped pellets by applying pressure and then calcinated in air at 1400 K for 24 h and slowly cooled to room temperature. 2.1. Characterization The powder x-ray diffraction (XRD) pattern is recorded using Rigaku x-ray diffractometer. Fourier transform infrared (FTIR) spec- trum is recorded using Bruker-Tensor-37 spectrometer in the frequency range 400–2000 cm 1 . The dielectric constant and ac conductivity are measured with a parallel plate capacitor coupled to a precision LCR metre (Agilent 4284 A) in the frequency range 75 kHz–5 MHz, above room temperature. The sample is pressed into Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/ssc Solid State Communications 0038-1098/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ssc.2012.12.019 n Corresponding author. Tel.: þ91 9719006563. E-mail address: s.husain@lycos.com (S. Husain). Solid State Communications 157 (2013) 29–33