Grain size-dependent dielectric, piezoelectric and ferroelectric properties of Sr2Bi4Ti5O18 ceramics

• Published in: Journal of materials science 2016-10, Vol.51 (20), p.9253-9266
• Main Authors: Shet, Tukaram, Bhimireddi, Rajasekhar, Varma, K. B. R.
• Format: Article
• Language: English
• Subjects: Ceramic powders; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Coercivity; Coupling coefficients; Crystallites; Crystallography and Scattering Methods; Curie temperature; Curvature; Dielectric properties; Ferroelectric materials; Ferroelectricity; Grain boundaries; Grain growth; Grain size; Materials Science; Original Paper; Phase transitions; Physical properties; Piezoelectricity; Polymer Sciences; Powder compacts; Sintering (powder metallurgy); Sol-gel processes; Solid Mechanics; Temperature; Temperature dependence; Transition temperature
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-016-0172-5

Fine powders comprising nano-crystallites of Sr 2 Bi 4 Ti 5 O 18 (SBT) were synthesized via citrate-assisted sol–gel route. Different ceramics of SBT with different grain sizes (93 nm–1.42 μm) were fabricated by varying sintering temperatures and durations. The usage of nano-crystalline powders for fabricating ceramics facilitated lower sintering temperatures. The grain growth in these powder compacts was found to be controlled by the grain boundary curvature mechanism, associated with the activation energy of 181.9 kJ/mol. Interestingly, with a decrease in grain size there was an increase in structural distortion which resulted in a shift of Curie temperature (phase transition) toward higher temperatures than that of conventional bulk ceramics. Extended Landau phenomenological theory for the spherical ferroelectric particles was invoked to explain experimentally observed size-dependent phase transition temperature, and the critical size for SBT is predicted to be 11.3 nm. Grain size-dependent dielectric, ferroelectric and piezoelectric properties of the SBT ceramics were studied and the samples comprising average grain size of 645 nm exhibited superior physical properties that include remnant polarization (2 P r ) = 16.4 μC cm −2 , coercive field ( E c ) = 38 kV cm −1 , piezoelectric coefficient ( d 33 ) = 22 pC N −1 and planar electromechanical coupling coefficient ( k p ) = 14.8 %.