Gd/Mn Co-Doped CaBi4Ti4O15 Aurivillius-Phase Ceramics: Structures, Electrical Conduction and Dielectric Relaxation Behaviors

In this work, Gd/Mn co-doped CaBi4Ti4O15 Aurivillius-type ceramics with the formula of Ca1-xGdxBi4Ti4O15 + xGd/0.2wt%MnCO3 (abbreviated as CBT-xGd/0.2Mn) were prepared by the conventional solid-state reaction route. Firstly, the prepared ceramics were identified as the single CaBi4Ti4O15 phase with orthorhombic symmetry and the change in lattice parameters detected from the Rietveld XRD refinement demonstrated that Gd3+ was successfully substituted for Ca2+ at the A-site. SEM observations further revealed that all samples were composed of the randomly orientated plate-like grains, and the corresponding average grain size gradually decreased with Gd content (x) increasing. For all compositions studied, the frequency independence of conductivity observed above 400 degrees C showed a nature of ionic conduction behavior, which was predominated by the long-range migration of oxygen vacancies. Based on the correlated barrier hopping (CBH) model, the maximum barrier height W-M, the dc conduction activation energy E-d(c), as well as the hopping conduction activation energy E-p were calculated for the CBT-xGd/0.2Mn ceramics. The composition with x = 0.06 was found to have the highest E-dc value of 1.87 eV, as well as the lowest conductivity (1.8 x 10(-5) S/m at 600 degrees C) among these compositions. The electrical modules analysis for this composition further illustrated the degree of interaction between charge carrier beta increases, with an increase in temperature from 500 degrees C to 600 degrees C, and then a turn to decrease when the temperature exceeded 600 degrees C. The value of beta reached a maximum of 0.967 at 600 degrees C, indicating that the dielectric relaxation behavior at this temperature was closer to the ideal Debye type.

Automated summary

In this study, Gd/Mn co-doped CaBi4Ti4O15 ceramics were prepared and their structural and electrical properties were investigated. It was found that Gd3+ successfully substituted for Ca2+ at the A-site, and the grain size decreased with increasing Gd content. The maximum barrier height and activation energy were calculated for a specific composition, and the relationship between conductivity and temperature was determined.