Crystal structure refinement and investigation of electrically heterogeneous microstructure of single phased Sr substituted BaTiO3 ceramics

• Single phased Sr substituted BaTiO3 ceramics prepared via solid state reaction.
• Rietveld refinement of the ceramics showed tetragonal symmetry, P4mm space group.
• Linear decrease in Curie temperature was observed with increase in Sr substitution.
• Multiple activation energies revealed electrically heterogeneous microstructure.
• Conduction and relaxation were attributed to oxygen vacancies.

Single phased Sr substituted BaTiO3 ceramics were synthesized via solid state reaction technique and were found to crystallise in tetragonal symmetry with P4mm space group using Rietveld refinement. With increase in Sr content the tetragonality was reduced and the Curie temperature decreased at rate of 3 K/mol%. The contribution of grain interiors and grain boundaries to conduction and relaxation mechanisms was discerned on basis of ac conductivity, impedance and modulus formalisms. Three conduction mechanisms were observed in grain interiors; two via conducting electrons from VO′ and VO″ and third one via oxygen vacancies itself. The relaxation at grain boundaries was attributed to the defect associate (Vo″-2Ti3+). Saturated hysteresis loops confirmed the ferroelectric nature of the ceramics. The remnant polarization Pr and the coercive fields Ec decrease with increase in Sr content.