STUDY OF SAMPLE - ELECTRODE INTERFACE IN CERAMICS BY USING IMPEDANCE SPECTROSCOPY *Shukdev Pandey, Om Parkash, Devendra Kumar Department of Ceramic Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi, Uttar Pradesh, India *Address for Correspondence: Shukdev Pandey, Department of Ceramic Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi, Uttar Pradesh, India; E mail ID: spandey.rs.cer12@iitbhu.ac.in ABSTRACT The electrical behavior of ceramic system BaFe Ti O (x= 3% and 5% )containing coexisting x 1-x 3 tetragonal and hexagonal phases was studied by using Impedance Spectroscopy as function of temperature ( 450K – 650K) in the frequency range 20 Hz – 1 MHz .Equivalent circuit model comprising four parallel RC's connected in series corresponding to the two phases, grain boundary region and contact electrode represented the data well. When the sample contained predominantly tetragonal phase, the time constant for sample - electrode interface showed an Arrhenius type behavior with activation energy (0.58 ± 0.05) eV whereas when the sample contained both tetragonal and hexagonal phases no clear trend was observed. These observations are useful in selection of electrodes for applications and for developing techniques for dielectric studies of materials when measurements are done as function of temperature. Keywords: Ceramics; Impedance Spectroscopy; Equivalent Circuit Model; Sample-Electrode Interface; CNLS. Ceramics are inorganic non-metallic solids that have been processed and shaped by heating at high temperatures. Modern day ceramics include oxides, nitrides, carbides etc. and constitute a large fraction of technologically useful materials. Ceramics used in electrical and electronics industry are broadly termed as electro-ceramics and are heavily used in electrical insulators, TV balunes, mobile antennas and speakers, substrates for electronic circuits, computer memories, magnetic recording heads, high temperature heating elements, cryogenic sensors etc. By utilizing various processing strategies such as heating/cooling rates , presence of additives, developing certain microstructures, controlling the grain sizes etc. ,certain interesting and useful properties not so possible in single crystalline form can be imbibed in ceramics . Together with this, due to ease in preparation, processing and casting in desired shapes and sizes, materials in [1-5] ceramic form are preferred for applications . One of the traditional and still popular methods of preparation of a ceramic is the so called solid state reaction method which involves mixing the components in appropriate amounts in a mill and then heating the mixture at suitable elevated temperature so that reaction takes place in solid state. Other methods such as wet chemical and sol-gel methods have been developed that are used based on various considerations such as purity, homogeneity, particle size etc. The as- prepared ceramics are usually in powder form that are processed and shaped for device applications. The ceramic piece thus comprises small crystallites called grains that are joined together in random orientations. The joining region called the grain boundary has, due to mismatch, strained bonds. Therefore properties of grain boundary are different from those of grains and highly depend upon the processing variables such as heating/ cooling rates and atmosphere. Ceramics prepared by controlled crystallization of glass are called glass-ceramics. In glass ceramics the grain boundary consists of uncrystallized glassy [1,2,6] matrix . Usually, it is the interplay of 'grain' and 'grain boundary' behaviour that bestows ceramics with several technologically useful properties. The INTRODUCTION www.ijsir.co.in 43 International Journal of Scientific and Innovative Research 2018; 6(1) : 43 ‐ 52 P‐ISSN 2347‐2189, E‐ ISSN 2347‐4971