Investigation on microstructure and dielectric behaviour of (Ba0·999 − x Gd0·001Cr x )TiO3 ceramics
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Ceramics of BaTiO3 co-doped with Gd and Cr at Ba-site was synthesized via solid-state reaction route. Surface morphology shows the increase in grain size with the increase of Cr-content below 3 mol%. The high value of ε in the synthesized samples is associated with space charge polarization and inhomogeneous dielectric structure. Gd is diffused well into the most of Ba sites and vacancies leaving very few defects or voids for the generation of absorption current which results in dielectric loss. Below 3 mol% of Cr-concentration, dissipation factor was improved. Increase in a.c. conductivity with rise of temperature is due to increase in thermally activated electron drift mobility of charges according to the hopping conduction mechanism. Moreover, samples show the positive temperature coefficient of conductivity, which is most desirable for developing highly sensitive thermal detectors and sensors. Also, higher frequency indicates motion of charges in the ceramic samples.
KeywordsCeramics chemical synthesis microstructure dielectric properties positive temperature coefficient of conductivity
Two of the authors (SM and RS) gratefully acknowledge UGC, New Delhi, for sanction of RFSMS fellowship no. F.4-1/2006(BSR)/11-129/2009(BSR). (RS) also wishes to acknowledge DST, New Delhi, for award of a INSPIRE fellowship no. DST/INSPIRE fellowship/2011/(31). (NS) acknowledges UGC, New Delhi, for grant of a UGC-MRP project fellowship vide F.No. 37-177/2009(SR). Thanks to Prof. Aslam, Mr Anand Raut and Mr Shripal Singh, Department of Physics, Indian Institute of Technology, Mumbai, for extending SEM facility.