Effect of Sr²⁺doping on the phase transition of BaTiO₃ lead-free ferroelectric ceramics

The single phase Ba_1−xSr_xTiO₃ (x = 0, 0.4, 0.8) ceramic compositions were fabricated through solid state (mixed oxides) method calcined at 850 °C and sintered at 1200 °C in air. The XRD patterns revealed the single phase BaTiO₃ composition with a space group of pm-3m. The shifting of the (1 0 0) XRD peak to higher 2θ values is accredited to the substitution of comparatively smaller ion of Sr²⁺ (1.4 Å) for larger Ba²⁺ (1.6 Å) ion following the Braggs diffraction law (2dsinθ = mλ). The phase transition or Curie point from polar ferroelectric phase to non-polar paraelectric phase of Ba_1−xSr_xTiO₃ was reported to decrease with increasing Sr²⁺ content in Ba_1−xSr_xTiO₃ compositions. The value of the dielectric constant decreased with increasing the content of Sr²⁺, which may be attributed to the substitution of comparatively smaller ion of Sr²⁺ for Ba²⁺ in the perovskite structured Ba_1−xSr_xTiO₃. (paper)