Composition and poling-induced modulation on photoluminescence properties for NBT- x BT: Pr 3+ ceramics

In this work, the modulation of photoluminescence (PL) properties, which was realized by the composition and poling-induced structural evolution, for the Pr3+ doped (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 (NBT-xBT: Pr3+) piezoelectric ceramics was systematically investigated. Based on the Rietveld refinement structural analysis, there were two distinct composition ranges characterized by different structural features for NBT-xBT: Pr3+ ceramics at room temperature: (i) rhombohedral R3c+monoclinic Cc phases for the compositions of x≤0.03, and (ii) tetragonal P4bm+monoclinic Cc phases for 0.04≤x≤0.07. It was interesting to notice that the PL emission intensity is positively correlated with the phase fraction of Cc, which is closely related to the crystal symmetry of NBT-xBT: Pr3+ ceramics. The compositions with x≤0.06 underwent an irreversible phase transformation on the application of electric field. The dielectric and Raman measurement revealed a transition from a relaxor state to a normal ferroelectric for the x≤0.06 compositions under an applied poling electric field, with not only the reduction in the in-phase octahedral tilting disorder but also the establishment of long-range ordering. These electric field-induced structural changes were responsible for poling-induced PL quenching behaviors as a result of the increased local structure symmetry around doped Pr3+ ions in the poled ceramics.