Evidence of large hopping polaron conduction process in strontium doped calcium copper titanate ceramics

Abstract Strontium (Sr) doped Calcium Copper Titanate Ca 1−x Sr x Cu 3 Ti 4 O 12 with two values x  = 0 and x  = 0.05 commonly known as CSCTO ceramics have been obtained by using the semi wet route synthesis method. Rietveld refinement shows that the powders crystallize in the cubic perovskite related structure with Im3 space group. Scanning Electron Micrograph (SEM) analysis shows that the average grain size of ceramics becomes larger when Sr doping is considered. Both DC and AC electrical conductivity are investigated throughly in the temperature and frequency ranges between [373–653 K] and [20 Hz–1MHz], respectively. The values of the average activation energies for CSCTO-0 ( x  = 0) and CSCTO-5 ( x  = 0.05) were found to be 612 meV and 576 meV, respectively. In Fact, Sr doping has an effect on the broadening of the impurity band that can lead to a dramatic decrease in the activation conduction energy of CSCTO ceramics. A systematic study of AC electrical conductivity reveals that the predominant conduction mechanism existing in these ceramics is generated by large polaron hopping process. This mechanism has also been identified by the modulus analysis and confirmed by comparing the hopping polaron size with the lattice parameter.