Structural, electrical, and photoluminescence properties of Pr³⁺ doped Na_0.25K_0.25Bi_2.5Nb₂O₉ bismuth layer-structure ceramics

In this paper, Pr³⁺ doped Na_0.25K_0.25Bi_2.5Nb₂O₉ (NKBN-xPr³⁺) ceramics were successfully prepared via a conventional solid-state reaction process. The structural, dielectric, and piezoelectric properties as well as photoluminescence performance of the samples were systemically studied. All the ceramic samples possessed a pure two-layered bismuth layer-structure with the A2 ₁ am space group. Raman spectra revealed that the doped Pr³⁺ ions mainly replaced Bi³⁺ at the A-sites in the pseudo-perovskite layers. With increasing Pr³⁺ concentration, the Curie temperature and the maximum dielectric constant of the samples decreased, while the piezoelectric constant d ₃₃ increased from 15 pC/N for x = 0 to 21 pC/N for x = 0.01. Addition, d ₃₃ remained almost unchanged for all samples when the annealing temperature was lower than 450 °C. Under excitation with 452 nm light, the obtained samples exhibited a typical emission of Pr³⁺ ions, with the strongest red emission peak centered at 609 nm. The corresponding color tone of the ceramics shifted from red-orange to orange-yellow with increasing Pr³⁺ doping. The thermal quenching behavior of the photoluminescence of the x = 0.01 sample was also investigated in detail, and the thermal quenching activation energy was calculated to be 0.4473 eV. Our study indicated that NKBN-xPr³⁺ ceramics may have potential applications in multi-functional devices.