Role of charge-compensation process on the structural, microstructure and electrical properties of pure and Nb-doped Sr2SnO4

This article explores the charge compensation method by synthesising Sr2SnO4, Sr2Sn0.99Nb0.01O4, and Sr1.995Sn0.99Nb0.01O4. The synthesis of a monophasic, tetragonal sample was achieved using a typical ceramic approach and high-temperature heat treatment. The XRD followed by Rietveld refinement, confirmed the crystallization of material under the space group I4/mmm. The crystallite sizes for all samples determined to be less than 50 nm, while the micro-strain falls within the range of (1.78-2.93)x10-3. The microstructure exhibits a cuboidal shape for all samples, and the grain size is observed to decrease with the addition of Nb. The dielectric characteristics of the samples indicate the existence of Maxwell-Wagner and Orientational polarization in the sample. The sample Sr2Sn0.99Nb0.01O4 demonstrates a greater conductivity value compared to Sr1.995Sn0.99Nb0.01O4. This is attributed to the presence of excess electrons that compensate for the overall charge, as opposed to Sr1.995Sn0.99Nb0.01O4 where the extra charge is compensated by a cationic vacancy V_Sr^''. The time-temperature-superposition principle (TTSP) is applicable to all compositions and indicates that similar sources are responsible for both conduction and relaxation processes. The dielectric permittivity and dissipation factor are found to be in the range of 150 to 175 and 0.2 to 0.5, respectively. This suggests that they have potential for future use in millimeter-wave communication with dielectric resonator antennas (DRAs). Due to the presence of oxygen ions and the ability to conduct both ions and electrons, at temperatures above 400℃, it is a suitable choice for electrode materials in the application of intermediate temperature solid oxide fuel cell (IT-SOFCs). Exploring the manipulation of defects using electrical and ionic charge compensation methods shows potential for enhancing materials in semiconductor technology.