Site-Selective Eu³⁺ Doping and Enhanced Luminescence from Eu³⁺ at B Sites in Perovskite-Type Strontium Zirconate and Hafnate

To achieve efficient Eu³⁺ luminescence, site-selective doping of Eu³⁺ was attempted in perovskite-type (ABO₃) SrMO₃ (M = Zr, Hf). In contrast to CaMO₃ and BaMO₃, it was found that the doping sites of Eu³⁺ (Eu_Sr^• or Eu_Zr^′/Eu_Hf^′) could be highly controlled in SrMO₃ by a codoping technique. This was mainly because the size of Sr²⁺ was suitable for the site-selective doping of Eu³⁺ in SrMO₃. The codoping of small Ga³⁺ at B sites (Ga_Zr^′/Ga_Hf^′) was carried out for A-site doping of Eu³⁺, whereas the codoping of large La³⁺ at A sites (La_Sr^•) or small Nb⁵⁺ at B sites (Nb_Zr^•/Nb_Hf^•) was conducted for B-site doping of Eu³⁺. As a result, the proportion of Eu³⁺ at A and B sites became more than 90% by the A-site and B-site doping, respectively, from the analysis of X-ray absorption near-edge structures for the Eu L₃ edge. Eu³⁺ ions were driven to intentional sites by codoping due to the dual effects of charge compensation and ionic size balance. The high Eu³⁺ proportion at B sites, viz. the almost complete B-site doping, led to the findings of significant enhancement of Eu³⁺ luminescence, which was derived from the magnetic dipole transitions from ⁵D₀ to ⁷F₁ states. The quantum efficiencies of the enhanced luminescence from SrMO₃ doped with Eu³⁺ at B sites exceeded 50% at room temperature.