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

Daowen Wu; Huajiang Zhou; Lingfeng Li; Yu Chen

doi:10.3390/ma15175810

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

Materials (Basel). 2022 Aug 23;15(17):5810. doi: 10.3390/ma15175810.

Authors

Daowen Wu¹, Huajiang Zhou¹, Lingfeng Li¹, Yu Chen^{1

2}

Affiliations

¹ School of Mechanical Engineering, Chengdu University, Chengdu 610106, China.
² Institute of Advanced Materials, Chengdu University, Chengdu 610106, China.

Abstract

In this work, Gd/Mn co-doped CaBi₄Ti₄O₁₅ Aurivillius-type ceramics with the formula of Ca_1-xGd_xBi₄Ti₄O₁₅ + 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 °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 × 10^-5 S/m at 600 °C) among these compositions. The electrical modules analysis for this composition further illustrated the degree of interaction between charge carrier β increases, with an increase in temperature from 500 °C to 600 °C, and then a turn to decrease when the temperature exceeded 600 °C. The value of β reached a maximum of 0.967 at 600 °C, indicating that the dielectric relaxation behavior at this temperature was closer to the ideal Debye type.

Keywords: CaBi4Ti4O15; dielectric relaxation; electrical conduction; ion doping; oxygen vacancies.

Grants and funding

This work was supported by the State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and astronautics (Grant No. MCMS-E-0522G01), the State Key Laboratory of Crystal Materials, Shandong University (Grant No. KF21-08), and the Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion (Grant No. MATEC2022KF001).