Fabrication, structure, and frequency-dependent electrical and dielectric properties of Sr-doped BaTiO3 ceramics

Lead-free strontium-doped ferroelectric ceramics with the compositional formula Ba1-xSrxTiO3 (barium strontium titanate, BST) M (x = 0, 0.25, 0.3, and 0.35) are effectively synthesized through a solid-state reaction. The as-prepared samples are characterized by X-ray diffraction (XRD) and Raman spectroscopy. Further dielectric properties and impedance are examined in detail. XRD and Raman studies reveal that the lattice constant, unit cell volume along with tetragonality ratio change with the Sr concentration, Curie temperature (T-c), and dielectric constant along with dielectric loss factor decrease with increasing Sr2+ ions in BST. A stable dielectric constant is detected in a wide frequency range of 1-1000 kHz. Curie-Weiss law and theoretical estimations indicate a large difference in structural disorder in BaTiO3 (barium titanate, BT) ceramics. Consistent with applied temperature and frequency, a noteworthy change is observed in dielectric constant and loss tangent behavior between lowly and highly doped BT samples. Diffusivity decreases with the increase in Sr2+ amount up to x = 0.3. The relaxation response in BST ceramic is observed for higher values of x. Impedance spectroscopy reveals those oxygen vacancies (OVs) are responsible for conduction in BST ceramics. This study is a systematical investigation on the relationship among the structure, dielectric, and impedance properties of Sr2+ substituted BT ceramics.