Luminescence and Location of Gd³⁺ or Tb³⁺ Ions in Perovskite-Type LaScO₃

The luminescence properties of Gd³⁺ or Tb³⁺ ions at La and Sc sites were investigated in LaScO₃ with a distorted perovskite-type structure (ABO₃). Although the luminescence of lanthanide ions located at B sites is not common and has not been examined in detail, Gd³⁺ or Tb³⁺ luminescence from B sites and A sites is clearly observed in Gd³⁺- or Tb³⁺-doped LaScO₃. The differences in the luminescence characteristics concern peak positions, peak shapes, and decay time, which are all influenced by the crystal field and the site symmetry. The UV luminescence of Gd³⁺ at B sites shows a red shift compared to Gd³⁺ at A sites, and the green luminescence of Tb³⁺ at B sites contrasts with the blue-violet and green luminescence of Tb³⁺ at A sites. The decay time of the luminescence from B sites is systematically longer than that from A sites in both the Gd³⁺ and Tb³⁺ cases

Luminescence and Valence of Tb Ions in Alkaline Earth Stannates and Zirconates Examined by X‑ray Absorption Fine Structures

The difference in Tb³⁺ green luminescence intensities in doped perovskite­(ABO₃)-type alkaline earth stannates, AeSnO₃ (Ae = Ca, Sr, Ba), and the Mg codoping effect on the luminescence intensities in doped CaMO₃ (M = Sn, Zr) were investigated utilizing the X-ray absorption fine structures (XAFS) of the Tb L_III absorption edge. It is considered that the local symmetry at A sites is responsible for the different Tb³⁺ luminescence intensities in AeSnO₃ (Ae = Ca, Sr, Ba) doped with Tb ions at A sites. However, it was found from the XAFS spectra that some Tb ions are unintentionally stabilized at B sites as Tb⁴⁺, especially in BaSnO₃. Not only the central symmetry for Tb³⁺ at A sites but also the presence of Tb⁴⁺ at B sites were considered to bring about the absence of Tb³⁺ luminescence in doped cubic BaSnO₃. No obvious changes in the Tb³⁺ local structure at A sites were detected between Tb single doped and Tb–Mg codoped CaMO₃ (M = Sn, Zr) from the extended XAFS oscillation, but the trace of Tb⁴⁺ at B sites in the Tb single doped sample was observed in the X-ray absorption near edge structures. It is, therefore, considered that the Tb³⁺ luminescence enhancement by Mg codoping is primarily attributed to the charge compensation rather than the changes in the local structure around Tb³⁺ at A sites