Photoluminescence and electrical properties of Eu3+-doped Na0.5Bi4.5Ti4O15-based ferroelectrics under blue light excitation

Na_0.5Bi_4.5?x Eu _x Ti₄O₁₅ (NBT- _x Eu³⁺) ceramics with x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 and 0.40 were prepared by conventional ceramics processing. NBT-0.25Eu³⁺ ceramics show the strongest red and orange emissions corresponding to the ⁵D₀ → ⁷F₂ (617 nm) and ⁵D₀ → ⁷F₁ (596 nm) transitions, respectively. The strongest excitation band around 465 nm matches well with the emission wavelength of commercial InGaN-based blue LED chip, indicating that Eu³⁺-doped NBT ceramics may be used as potential environmental friendly red-orange phosphor for W-LEDs application. As an inherent ferroelectric and piezoelectric material, the electrical properties of this potentially multifunctional electro-optical material have been also studied. The introduction of Eu³⁺ distinctly increased the Curie temperature (T _C ) of NBT- _x Eu³⁺ ceramics from 640°C to 711°C as x ranges from 0 to 0.40. For higher temperature applications, the electrical conductivity was also investigated. The conduction of charge carriers in high-temperature range originates from the conducting electrons from the ionization of oxygen vacancies. High T _C and low tanδ makes Eu³⁺-doped NBTceramic also suitable for high temperature piezoelectric sensor applications and electro-optical integration.