Strong red emission and enhanced ferroelectric properties in (Pr, Ce)-modified Na_0.5Bi_4.5Ti₄O₁₅ multifunctional ceramics

Bismuth layer-structured ferroelectric (BLSFs) ceramics of Na_0.5Bi_4.5−x (Pr_0.5Ce_0.5) _x Ti₄O₁₅ (NBT-x(Pr, Ce), x = 0.000, 0.004, 0.008, 0.012) were prepared by a conventional solid-state reaction method, and the influence of (Pr, Ce) additive on the ferroelectric, dielectric, and photoluminescence properties of samples were investigated. It is found that all the samples have a bismuth oxide layered structure with a dense microstructure. After (Pr, Ce) doping, the samples showed a bright red photoluminescence. The sharp excitation peaks around 449, 480 and 491 nm correspond to the ³H₄ → ³P₂, ³H₄ → ³P₁ and ³H₄ → ³P₀ transition, respectively. Upon the excitation of 492 nm light at room temperature, samples show two emission bands located at 611 and 656 nm, respectively. The strong red emission band centered at 611 nm is attributed to ¹D₂ → ³H₄ transition, and the weak red emission located 656 nm is due to the ¹D₂ → ³H₅ transition. In addition, it is an intrinsic ferroelectric and piezoelectric material, and the enhanced ferroelectric properties were obtained by (Pr, Ce) doping. At x = 0.004, the remnant polarization 2P _r reaches 13.54 μC/cm², together with a high Curie temperature (T _c = 662 °C) and activation energy of E _a = 0.83 eV. As a multifunctional material, the (Pr, Ce)-modified NBT piezoelectric ceramic may be useful in white LEDs, sensor and optical-electro integration.