Temperature-dependent Raman and dielectric studies of Sm and Zr Co-doped BaTiO₃ ceramics

Sm and Zr co-doped BaTiO₃ ceramics were investigated for their microstructure and dielectric characteristics. (Ba_{1 − x}Sm_x)(Ti_0.75Zr_0.25)O_3−δ (BSTZO) with x = 0.02, 0.04, and 0.06 mol% of ceramic compounds were prepared by solid-state reaction route. The primary objective is to obtain higher dielectric constant with lower dielectric loss in the proposed material composition. The prepared BSTZO and sintered compounds were found to be highly crystalline with a tetragonal perovskite structure. A typical X-ray photoelectron spectroscopy spectra of BSTZO sample with Sm = 0.02 mol% calcined at 1273 K revealed the elemental composition, binding energy, and chemical state of the elements. Oxygen vacancy concentrations evaluated by in situ high-temperature Raman spectroscopy in the temperature range of 301–773 K were found to decrease with increasing Sm³⁺ concentration and the substitution of the lowest concentration of Sm³⁺ (0.02 mol%) in the A site of the BSTZO was found to be higher (V_O^··= 1.98 × 10²¹ cm⁻³, at 773 K) than that of the other compositions. The measured maximum dielectric constant was found to be 1808, 2010, and 1736 for BSTZO pellet with x= 0.02, 0.04, and 0.06 mol%, respectively in the temperature range of 323–773 K and at frequency of 20 MHz. Among these compounds, (Ba_0.96Sm_0.04) (Ti_0.75Zr_0.25)O_3−δ has shown high dielectric constant and low loss tangent compared to other compositions.