Unveiling the role of ZrO2 doping in Sr2SmTi2Nb3O15 ceramics: From structural study to dielectric enhancement

Solid-state processing was used to synthesize tungsten bronze type (TTB) solid solutions, specifically Sr2Sm(Ti1xZrx)2Nb3O15 with x values of 0, 0.2, 0.3, and 0.4. The study examined the crystalline structure, optical properties, morphology, and electrical and dielectric characteristics of these compounds. X-ray diffraction revealed a tetragonal structure (space group P4bm). Scanning electron microscopy showed significant sample densification with grain sizes decreasing from 6.19 mu m to 2.78 mu m. Dielectric measurements indicated that the dielectric constant varied from 150 for x = 0 to 567.24 for x = 0.2, then decreased to 380.88 for x = 0.4, with the x = 0.3 compound having the lowest dielectric loss. The Curie temperature (Tc) decreased from 332 degrees C to 248.5 degrees C with increasing Zr content, corresponding with a reduction in grain size. The energy gap (Eg) narrowed from 2.914 eV to 2.714 eV as Zr content increased. AC conductivity increased with temperature and frequency. Electrical conductivity followed Jonscher's power law, with activation energies decreasing from 1.54 eV to 0.87 eV, explained by the small polaron tunneling (NSPT) model.