Host-to-Activator Energy Transfer Developed by Eu3+ Doping at B Sites in Perovskite-Type Strontium Stannate Phosphor

Site-selective doping and site-dependent luminescence of Eu³⁺ were examined in the perovskite-type strontium stannate host, SrSnO₃, which is reported as a transparent oxide semiconductor (TOS). The X-ray diffraction patterns and the spectra of the X-ray absorption near edge structure (XANES) for the Eu L₃ edge revealed that the site-selective doping of Eu³⁺ was achieved almost completely by Mg²⁺ and La³⁺ or Nb⁵⁺ codoping. The site-dependent Eu³⁺ luminescence was clearly observed in the codoped samples, and the luminescence derived from the magnetic dipole transitions from the ⁵D₀ to ⁷F₁ states was seen intensively from Eu³⁺ at the B sites, Eu³⁺(B). The intense luminescence from Eu³⁺(B) was found to occur only in the samples with a high Eu³⁺(B) proportion attained by La³⁺ or Nb⁵⁺ codoping. It is also noteworthy that the intense Eu³⁺(B) luminescence was obtained not by the charge transfer excitation for Eu³⁺(B) but by the excitation for the host of the SrSnO₃ TOS, revealing the efficient energy transfer from the host to Eu³⁺(B). The finding indicates that both the Eu³⁺ luminescence and semiconducting features could be available in SrSnO₃, which is preferable for optoelectronic applications such as cathodoluminescence and electroluminescence.