An efficient gel-combustion synthesis of visible light emitting barium zirconate perovskite nanoceramics: Probing the photoluminescence of Sm³⁺ and Eu³⁺ doped BaZrO₃

Barium zirconate (BZO) nanoceramics were synthesized using self-assisted gel-combustion route. BZO powders were characterized systematically using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) and photoluminescence (PL). Doping of Eu³⁺ and Sm³⁺ was confirmed by XRD. Intense blue and green emission was observed in undoped sample without activator ion. PL and EPR study shows the presence of oxygen vacancy (shallow and deep defect) is responsible for such visible emission. Bases on PL spectroscopy; it was inferred that majority of Sm³⁺ ion stabilizes at Ba²⁺ site without inversion symmetry though oxygen vacancies are introduced in vicinity to ensure local charge compensation whereas majority of Eu³⁺ ion occupies Zr⁴⁺ site. The fact that in Ba_1−xEu_xZrO₃; electric dipole transition (EDT) is much more intense than magnetic dipole transition (MDT); asymmetry ratio is found to be much greater than unity (I⪢1) indicating majority of Eu³⁺ at site without inversion symmetry in BaZrO₃ perovskite. The actual site symmetry for Eu³⁺ ion in barium zirconate was also evaluated based on stark splitting pattern which comes out to be C₆ in BaZrO₃.This is also reflected in the trend of Judd Ofelt (JO) parameter; Ω₂ value was found to be greater than Ω₄ indicating high covalency and low symmetry around Eu³⁺ ion.