Structural and Electrical Characterization of SrMn_0.97Ce_0.03O₃ Ceramics

Abstract

Cerium doped strontium manganese (SrMn_0.97Ce_0.03O₃) ceramics was prepared by solid state reaction route. The structural analysis suggests a hexagonal structure (P63/mmc) with refine lattice constants are;$\text{ a }=\mathrm{b}=0.5532\mathrm{nm},\mathrm{ }\mathrm{c}=0.9108\mathrm{nm},\mathrm{ }\mathrm{\alpha }=\mathrm{\beta }={90}^{\mathrm{°}},\mathrm{ }\mathrm{\gamma }={120}^{\mathrm{°}},$ $\rho =5.42$ g/cm³, and $V=241.38\times {10}^6\mathrm{ }{\mathrm{pm}}^3.$ The average crystallite size and micro-strain in the material are 35.8 nm and 0.0717%, respectively. The study of SEM micrograph suggests a highly dense material with small porosity. It is clearly noticed that material has well defined grains surrounded by grain boundaries with average grain size is 9.5 μm, which play important role to define electrical properties. Activation energy increases from 275 meV to 504 meV with temperature in the material confirms a thermally activated conduction process, which is also well supported from decreasing tendency of diameter of Nyquist plots. Temperature dependent relaxation time graph suggests two conduction channels (E_a1=212 meV & E_a2 = 51 meV) i.e. immobile charge carriers at low-temperature while defects at higher temperature. The gap between the peak of ${\text{ Z}}^{\text{''}}$ and ${\text{ M}}^{\text{''}}$ is becoming wider with temperature confirming non-Debye-type relaxation character. The bulk resistance (R_b) decreases from 8.622 × 10³ Ω at 25$\mathrm{°}$ C to 1.380 × 10² Ω at 500$\mathrm{°}$ C after fitting (CQR) (CR) model with Nyquist plot supporting the NTCR behavior of the material, which is well supported from Cole-Cole plots. Prepared material can be used in cathode for making solid oxide fuel cells (SOFCs) and biosensors.

Keywords:

• Hexagonal
• lattice strain
• activation energy
• SOFCs
• non-Debye relaxation
• Nyquist plots